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The last update: July 4, 2010
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ANNOTATION
Here the author's idea (first it was published in IZVESTIA ACADEMY
OF SCIENCES OF USSR in 1991, and now it is already rather popular among
Tunguska researchers) is explained that the famous 1908 Tunguska event
in Siberia was not an impact of a stony asteroid/meteorite or a comet, but a
manifestation of geophysical (terrestrial) processes: roughly speaking, a
result of coupling between tectonic and atmospheric processes in very rare
combination of favourable geophysical factors.
In general it is based on the following:
Simultaneous realization of all these geophysical phenomena together
with Tunguska as just pure accidental coincidence is very unlikely.
Remarkably, that on small scales similar geophysical micro-Tunguskas
occur rather often.
The exact physical mechanism of Tunguska event is still disputable.
In my opinion electromagnetic phenomena play large role in it.
Here is a note from SCIENCE magazine - a reaction on the above-mentioned discussion of Tunguska at the Brunel Univ. conference (SCIENCE's issue of Sept.13, 2002, p.1803):
On the morning of 30 June, 1908, in the remote Tunguska forest of Siberia,
a vast explosion charred and flattened trees across an area nearly as large
as Rhode Island.
Scientists have been mystified for years over the cause, although
prevailing wisdom has it that an extra-terrestrial chunk of ice or rock
struck Tunguska (Science, 20 August 1999, p. 1205).
At a conference in London last week on environmental
catastrophes, physicists from Russia and Germany rejected the 'ET
hypothesis.' Andrei Ol'khovatov, formerly of the Soviet Radio Instrument
Industry Research Institute, noted that decades of research has failed to
find definitive traces of extraterrestrial material. No impact crater has
been found and, more tellingly, patches of trees were left untouched near
the epicenter of the blast.
Wolfgang Kundt, an astrophysicist from Bonn University, Germany,
then proposed an alternative scenario: a massive gas explosion. A large
natural gas deposit lies below the site, a well-known fact unconnected to
the event until now, he said. Kundt has modeled a Tunguska 'outgassing' and
says it would fit with eyewitness accounts of the event.
"The geophysical hypothesis is a fresh idea," says Jesus Martinez-Frias of
the National Aerospace Institute in Madrid, Spain "It could be the answer."
But Ol'khovatov believes Tunguska was a "poorly understood strong coupling
between subterranean and meteorological phenomena" that science is not yet
ready to understand.
1. INTRODUCTION
2. THE PROBLEMS OF THE METEORITE FALL INTERPRETATION
2.1. THE EYEWITNESSES ACCOUNTS
2.2. THE FOREST FALL
2.3. THE TREES BURN
2.4. THE SEISMIC PHENOMENA
2.5. THE CHEMICAL TRACES
2.6. THE BIOLOGICAL CONSEQUENCES
2.7. THE SKY GLOW
3. THE TECTONIC INTERPRETATION
3.1. LUMINOUS EFFECTS OF TECTONIC ACTIVITY
3.2. MAIN FEATURES OF THE TECTONIC EXPLOSIVE EVENTS (GEOMETEORS)
3.3. EXAMPLES OF NNE (GEOMETEORS)
3.4. THE TECTONIC AND METEOROLOGICAL ACTIVITY AT THE
SITE AND THE TIME OF THE TUNGUSKA
3.5. THE PROPOSED SCENARIO OF THE TUNGUSKA
3.6. THE EYEWITNESSES ACCOUNTS
3.7. THE FOREST FALL
3.8. THE TREES BURN
3.9. THE SEISMIC PHENOMENA
3.10. THE CHEMICAL TRACES
3.11. THE BIOLOGICAL CONSEQUENCES
3.12. THE SKY GLOW
3.13. OTHER TUNGUSKAS
4. CONCLUSION.
6. REFERENCES
The problem of the nature of the 1908 Tunguska event has already excited
researchers over the course of many decades, and there is no consensus on
Tunguska still (see results of "what was Tunguska" internet poll
here
).
In the morning of June 30,
1908, the ground trembled north and northwest of Lake Baikal in Central
Siberia, and underground jolts struck panic into the hearts of the local
population. Reports of a glowing body flying over came from various points
of the territory. The Tunguska forest fall, called the "impact/explosion
site" or the "epicenter" was discovered just in 1927 at
61 N & 102 E, i.e. in the northern part of the Tunguska event manifestations
region. Various conjectures were soon offered in 1908 to explain the nature
of the event. The most popular were a meteorite fall, a ball lightning
(or its formation) and an earthquake (because of the seismic phenomena).
Since official science of the time put in doubt the existence of ball lightning,
while the possibility of glow occurring during earthquakes was, as a rule,
rejected, and a false report about a meteorite fall near a town of Kansk
appeared, the general consensus was that a very large meteorite had come
down in Siberia. Attempts to put forward any other interpretation had been
quashed for many years.
Since that time the situation with the "meteorite fall" rather resembles
a pendulum: one group of scientists turns up new strong evidences that it
couldn't have been an asteroid made of stone or iron, thus it had to be a
comet.
Pretty soon, another group of scientists comes up with new strong
arguments that Tunguska could not have been a comet, thus it must have been
an asteroid!
The number of supporters of each idea varies with time.
The latest maximum for the "asteroid" was around 1995. Since then,
the attractiveness of an asteroid explanation seems to decline again.
These swings hint that both groups are right and wrong at the same
time: Tunguska 1908 was neither an asteroid, nor a comet. But then,
what was it?
Many researchers seeing the failure of asteroid/comet interpretation proposed other ideas: a "black hole", an "antimatter bullet", a "mirror matter" asteroid, and, of course, UFO (the latter one is, no doubt, the most correct: indeed the event was related with some "unindentified flying object", or sooner with "objects", as it will be shown below!).
In late 1980-s I came up with the idea that Tunguska event was something
completely different, not a cosmic, but a geophysical event, associated with
tectonic processes. My idea, which in
the meantime has been presented at several scientific conferences as well
as in scientific journals (including such as SCIENCE and NEW SCIENTIST),
should not be confused with an earthquake,
although earthquakes were indeed associated with the 1908 explosion.
It was a more complicated event of tectonic origin in which atmospheric
processes played a large role. So probably we can call Tunguska
as tectono-atmospheric phenomenon. Now we can just to admit that it
was related with some still poorly understood processes of the Earth
electricity, but it is just a speculation.
Unfortunately, till now, such phenomena are a little known and poorly
understood. Moreover, there is no scientific term accepted for the
phenomena still. I prefer to call it as None-local Natural Explosion (NNE),
or geophysical meteor (geometeor), which probably sounds better (you
can read about it here). In a very simplified
form often it can be imagined as an explosion of a high-speed ball-lightning
tectonic origin.
In [1] the author ("the author" in the present paper means
"the present author" i.e. A. Ol'khovatov, unless otherwise stated)
have published the first time that the Tunguska was a tectonic (endogenic)
origin. Later this interpretation was developed in [2-5].
The author also reported it at the International conference "Tunguska
95" (1995) in Moscow, Tomsk, and at the
1998 International Tunguska conference in Krasnoyarsk and
Tunguska 2001 International conference in
Moscow (see a German Professor account on the latter
here).
No real arguments against were put forward. On the
contrary the idea gets a support by a group of geophysicists and geologists.
Also 3 my books on "tectonic" Tunguska were published in 1997-2008 (one
of them with a co-author).
Some time ago I got a proposal to place my point of view on Internet in English. The result is the present article. At first I write about the problems of the meteorite fall interpretation. Then I give examples of explosion-like manifestations of tectonic activity, which I proposed to call NNE (or geometeor), and apply them to the tectonic interpretation of the 1908 Tunguska.
In this article you can read also about modern mini-Tunguskas, and probable other Tunguskas of the past.
As it is very hard to permanently update this rather large article,
so in some places new references are given as Smith J.[2001], and you
can contact me for details.
Also I post the latest data in other
places of my www-site.
In the present paper a sign asterisk '*' means a multiplication, 'PI' means the PI-number i,e. 3.14159... , a sign '^' means raising to power (10^(-3)=0.001, for example).
Here are, for instance, some of the problems. The author also advises to read Vasilyev N.V. articles at http://www.galisteo.com/tunguska/docs/tmpt.html. and his the most "free/open" article here or here.
As above-mentioned, the reason to attribute the Tunguska to the fall of a meteorite was the reports about flying fiery body. For a science of 1908 it means just a meteorite and nothing else. But let's look at these 'flying bodies' carefully from our modern knowledge. Here and below after geographical denominations, the distances from the Tunguska explosion epicenter and azimuths in degrees from the epicenter, measured from the north to the east are also given ( and you can find a catalog of Tunguska witness's accounts in Russian here).
To better understand the situation, there is a map below (taken from the 1949 Krinov's book on Tunguska), with Krinov's marks of various Tunguska manifestations. I must add, that later it was discovered that Tunguska event manifested itself also in some farther areas, and there is spatial inhomogenity in its manifestations.
Let's read some witness's accounts.
Some details of the observed phenomena and especially the duration hardly conform to the meteorite fall.
Dyomin, Dmitriev, and Zhuravlev [1984] conducted analysis of "what did the witnesses see", based on complete data-set of the accounts [Vasilyev, Kovalevskii, Razin, et al., 1981]. The result is as follows:
Shape of the flying luminous body Percentage of accounts a ball-like 18.8 a cylinder 16.3 a cone-like 2.1 a star-like 3.4 a "tail-like" 14.0 a "snake-like" 2.3 a lightning-like 2.1 stripes of light 2.5 pillars of fire 4.9 a flame 10.3 a sparks-like 11.2 other forms 12.1
The eyewitness's accounts are hardly conformed with the meteorite fall. Even just in a few days-weeks after the event different time was given by different people, from early morning to the afternoon. So was the duration - from a few minutes to an hour. Astronomer Yevgenii Krinov, writing in his book "The Tunguska meteorite" published in 1949, about this side of evidence frequently uses phrases like, "the eyewitnesses either confused the cardinal points or just forgot the details".
All researchers noted, however, that the stories told by the local Evenks sounded true and were nearly always confirmed by other evidences later. The following story was typical for the area close to the epicenter. Two Evenk brothers, Chuchancha and Chekaren, sleeping in their tent (tepee) were suddenly awaken by shaking. They heard whistling sounds and "sensed a strong wind". One of them was pushed so heavily that his head struck a supporting pole and he fell on the hot embers in the fire-place. From outside came a hideous noise and sounds of trees falling. The brothers were about to dash out of the tent when a deafening thunderbolt clapped. The ground started to tremble and sway, and, a ferocious gust of wind toppled the tent. One of the men saw from under the immobilizing poles falling trees, their branches set on fire, and the dry unbrushed and moss burning. All the place was wrapped in smoke and it was so hot the brothers feared they "could be grilled alive". Suddenly a bright lightning flashed over the hill, as if another sun suddenly went up, and a series of thunderclaps followed immediately. Several more "lightning" flashes and claps of thunder, and the frightening sounds look like fading.
Evenk woman, Akulina, who was together with several Evenks in a tent (36 km, 121) said that suddenly "somebody strongly pushed our tent". Then it repeated again, and they fell on the ground. A loud noise came from outside, "somebody rattled and knocked the tent's cover". Suddenly bright light appeared, the bright sun was shining, strong wind was blowing". After "somebody fired (shot) and at once a whirlwind arrived". Akulina was frightened and lost consciousness. When she saw as a whirlwind "danced", she recovered. The whirlwind put her down. When she looked at the forest, she saw stems without branches and leaves. Many trees were put down. Wood bedding was burning. Ivan, her husband was thrown about 40 meters, his arm was broken and soon after he died (the another Evenk, who was in the tent told the same story, being interrogated independently).
Evenk, Ul'kigo (56 km, 176) said that suddenly in the early morning dogs began to howl, and small children cried. The persons inside the tent felt that "somebody began to knock the ground below them and to swing a tent". When Ul'kigo got out from the sleeping bag and began to put the clothes on, "somebody pushed the earth strongly" (right before it, "somebody fired from a gun a lot"). Suddenly again "just like somebody hit the earth". Utensils fell inside the tent. A loud thunderclap followed. When Ul'kigo got out from the tent, and looked at the sky, he suddenly saw a bright flash on the clear sky with following thunderclap. Ul'kigo was so frightened that he fell on the ground. He saw as wind put down trees and burning dry wood bedding. After Ul'kigo stood up, a whirlwind struck. The knocking, smoke and thunderclaps continued for some time.
Other eyewitnesses from the epicentral area gave similar reports. What has all that to do with the meteorite fall? Many other eyewitnesses also reported about luminous phenomena ( columns, stripes, lightning, flame, red sky glowing, etc.) which hardly resembled the meteorite fall.
Remarkably, that even supporters of the "meteorite fall" have to recognize that practically nobody of numerous witnesses saw any trail left by the "Tunguska fireball"...
On the basis of the eyewitness's accounts, three probable trajectories of the "Tunguska spacebody flight" were reconstructed (see also above). The first one was southern i.e. the meteorite flight from the south to the north (proposed and supported by Voznesenskii A., Kulik L. and Astapovich I. since 1920-s). Then in 1949 Krinov Ye. put forward the southeastern trajectory. Finally in the early 1960-s the eastern trajectory was proposed based on eyewitness accounts as well as on a pattern of the forest fall. Clearly, the meteorite could not have come from so many directions!
Remarkably that there are witnesses who stated that some anomalous phenomena commenced before 'fall' (i.e. before 00.14 UTC June 30, 1908). For example an outstanding Soviet ethnographer Sevyan Izrailevich Vainshtein
( http://en.tuvaonline.ru/2008/10/20/4204_vainshtein.html ) was in expeditions in the settlement Sulomai ( ~580 km to the west of the epicenter ) in the late 1940s. Some of the local residents were witnesses of Tunguska
( the Vainshtein's article in Russian is here: http://www.nkj.ru/archive/articles/14336/ ).
In brief: the witnesses stated that the anomalous skyglow commenced ~2 days before Tunguska! Also during Tunguska there was a windstorm in there which put down trees.
Vainshtein informed some scientists who studied Tunguska about the accounts after his return to Moscow, but the scientists did not believe them as the accounts contradict the meteorite-fall...
Below here is a map by W. Fast of the famous "butterfly" pattern of the Tunguska forest-fall.
Since mid-1960s numerous attempts were conducted to numerously stimulate the
forest fall by a meteoroid explosion (disintegration, to be exact). One of
the most detailed one was by Victor Korobeinikov, corresponding member of the
Russian Academy of Sciences, with co-workers at the Academy's Computer Center.
Their results are very remarkable in several aspects.
First they have determined that to produce the tree-fall, an altitude of
maximum energy output (caused by meteoroid's disintegration and the follow-up
aerobraking) of the hypothetical cosmic body (roughly speaking, the "explosion"
altitude) would be about 6-7 km (see picture 6 of their large article in: SLEDY
KOSMICHESKIKH VOZDEISTVII NA ZEMLYU; Novosibirsk, 1990, Nauka, p.69.). But we
know from large observational data-set that even much smaller meteoroids
disintegrate much higher in the atmosphere. Here are several well-documented
examples of confirmed falls (i.e. some residue were discovered):
- The Tagish Lake meteoroid (meteorite), which weighed about 200 t
(see SCIENCE, Oct.13, 2000, p.320 for details). On January 18, 2000 it
entered the Earth atmosphere with speed 15-16 km/s and "exploded" at 25 km
altitude.
- The St-Robert meteoroid (meteorite) entered the Earth atmosphere with
speed about 13 km/s over Canada on
June 15, 1994. It "detonated" at 36 km altitude (see METEORITICS & PLANETARY
SCIENCE, v.31, p.502 (1996)).
- The Jan.19, 1993 Lugo meteoroid (meteorite) over Italy "exploded" at
about 30 km altitude (see: ASTRON. ASTROPHYS., 337, L5-L8 (1998)).
And there is a well-known law, that with increase of meteoroid's dimensions,
its average strength decreases, and it disintegrates at higher altitude.
So the giant hypothetical "Tunguska stony meteorite" with mass in order of
100000-1000000 t (and, moreover, rather fragile and speedy comet!) was to
explode much more higher!
But, as it will be shown below, even a proposal that the Tunguska was
caused by some unusually strong exotic cosmic body would not help to explain
the forest fall.
It is based on the fact that the Tunguska spacebody explosion stimulation
undertaken by Victor Korobeinikov with his co-workers has shown the internal
energy of the spacebody to be commensurate with its kinetic energy to produce
the existent forest fall (otherwise the hypothetical meteoroid could not
"explode" switfly enough)[6]. In plain language, this means that the Tunguska
meteorite had to be an enormous block of super-explosive!
Moreover, it's possible to demonstrate that from the Korobeinikov's calculations the explosion of the hypothetical
Tunguska body must be practically completely due to its internal energy!
It's because the shape of the treefall reveals the presence of a significant
spherical component of the air-shock wave. But due to the law of a conservation
of a momentum, the explosion due to a kinetic energy don't produce a spherical
air-shock wave ( a total momentum of a spherical air-shock wave is zero,
while the total momentum of the bolide's generated air-shock waves is qual
to the momentum of the disintegrating meteorite). By the way, it is a strong
argument against modelling a meteoroid disintegration ("explosion") by
a method of "equivalent charge", i.e by exploding (really or numerally)
a charge (this method is often used for simplicity).
The absence of the spherical
component is clearly seen on Fig.4 of work [7]. In there the air-shock
wave of the "Tunguska meteorite" ( the latter is at 3 km/s speed,
i.e. practically already transferred all his momentum to air-shock waves)
is as must be - the conical one, which can't produce the shape of the Tunguska
forest fall!
Another intriguing detail of the forest fall is that despite the central
area of the forest fall is often considered to be covered with standing trees,
there are traces of the radial forest fall even in this area too! From the
traces, Kulik even came to conclusion about 2 closely spaced epicenters!
Anyway, the traces is one more problem for the meteorite interpretation
according to which just the vertical-falling shock wave could be present in
the epicentral area.
It is also remarkable, that Korobeinikov's and other results of the "Tunguska spacebody explosion" calculations point to an angle of inclination of the hypothetical spacebody trajectory must be about 40 degrees (otherwise it is not possible to get resemblance with the Tunguska forest-fall pattern), while from witness's accounts it must be no more than about 10-15 degrees (otherwise the fireball could not be seen far away). The only way out for meteorite advocates is to artificially insert "non-zero aerodynamic lift" into calculations, but avoiding such aspects as a reality of such "guided flight", and its circumstances (but calculations shows that the meteoritic body can't sustain such large overloads).
Detailed investigation of the Kulikovskii forest-fall conducted by various researchers has shown
that there are remarkable deviations of the forest fall from the radial pattern all over the area. The deviations are shown on the picture below (out of scale). The deviations are larger to the east of the epicenter (especially large in the south-east sector of the forest-fall).
The meteorite interpretation has large problems in explaining the deviations.
Another puzzle for the meteorite interpretation is the area of the forest fall on the ridge Chuvar (23 km, 279), which according to the local Evenks have formed the same morning as the general (Kulikovskii) one. It was discovered by the 1959 expedition. Its square is 30-40 sq. km. and the trees damage was found to occur in about 1908. The peculiarity of that forest fall is that trees were uprooted with their tops to the east (i.e. in the opposite of what expected from the meteorite fall direction). So the supporters of the meteorite fall prefer not to discuss it, or at least, talk just about accidental coincidence. And the coincidence, as could be seen on the picture below (out of scale) is rather remarkable...
The Kulikovskii (right on the picture above) and Chuvarskii (left on the picture above) forest-falls resemble as produced by intensive air-jets (like meteorological downburst and burst swath - see also below).
Some cases of the ignition of wood bedding were reported up to 34 km from the epicenter [9] and even probably farther (see section 2.1). But according to the Tunguska meteorite model it means that everything alive would completely burn at the epicenter. For example, according to the Tunguska meteorite model, the radiant exposure at the distances 5-9 km from the epicenter is about 300 J per sq. cm [7]. It means that right at the epicenter the radiant exposure is about 1200-1700 J per sq.cm!
In reality many groups of trees survived at the epicenter [10,11]. Moreover, some of the single standing trees were without any traces of burn [11]!
From the character of the trees damage it concludes that at first was the breaking of branches and then a burn at the site of the break [9, 12]. In other words, for the meteorite explosion interpretation it means that the air-shock wave from the explosion came faster than light impulse!
It was stated in 1996 that about 15-60% of survived trees near the epicenter have lightning-like damage [13]. So even L. Kulik thought that the fall was accompanied with lightnings. But how the modern meteorite fall theory could explain many thousands of lightning strikes?
The author also would like to mention the local Evenks reports about spots of melted sand and soil.
Here are just several examples of the seismic phenomena accompanied the Tunguska:
There are several intriguing aspects of the seismic observations. As,
for example, that in some places seismic disturbances occured several
hours later than in others. This effect is a typical for all witness's
accounts data, as it was discovered by Dyomin et al. in 1984, and the
effect is not on a border of statistical dispersion, but forms a secondary
weaker statistical maximum at about 12 noon.
Another aspect is the long duration of the seismic events (up to 45
minutes) as reported by numerous witnesses. It is in complete agreement
with recordings by nearest Irkutsk seismic station (see below).
The seismic disturbances were also recorded by 4 seismic stations:
Irkutsk, Tashkent, Tiflis, Jena [14, 15]. The Irkutsk one was the closest
one to the Tunguska
epicenter (about 970 km to the south from the epicenter). Ben-Menahem
[14], and Pasechnik [15] based their analysis on the assumption,
that the seismic recordings were caused by a meteorite explosion over
the epicenter, i.e. dimensions of the source of the seismic waves were
small compared with the distances (short-term point-like source).
In frames of this assumption they have obtained a time of
the earthquake origin 00.14 UT, June 30, and its magnitude 4.5-5. They
also stated that durations of the recordings at Irkutsk was up to
1.5 hours. The long duration of the recording is a puzzle for a long
time, as a seismic signal from a meteorite explosion must be of rather
short duration. Whipple (who did not see the original recording)
wrote in 1930: "A curious feature of the seismological record is the long
duration of disturbance at Irkutsk." He also questioned could
it be a misprint? Later, when it was confirmed, that it was not a
misprint, the question was practically ignored (or just assigned to weak
attenuation of seismometers without any consideration [15]).
However, my research has showed that the long duration of the signal
could not be explained by the weak attenuation [5]. I
have investigated Bulleten Postoyannoi Tsentralnoi Seismicheskoi Komissii
for 1908, and other similar documents, and have
discovered that durations of recordings by the Irkutsk seismic station of
many even much more intensive earthquakes were less than about 20 minutes
in that period of time. And indeed a real damping factor of such
seismometers was in order of 7-30, and a period of free oscillations
20-30 s [14,15], which implies full duration
of the free oscillations no more than about 15 minutes.
So the "meteorite explosion" theory can not explain the long duration of
seismic disturbances in Irkutsk.
And here I will show, that the "meteorite explosion" theory can not
explain the witness's reports on seismic phenomena too. Indeed, there is
an empiric formula for evaluation of seismic intensity
I at various distances R (km), from near surface earthquake with
magnitude M in the Baikal rift region:
Interestingly, there is a report from the Stepanovskii mine, a short distance from the town of Yuzhno-Yeniseisk, that an earthquake struck this area at 23.43 UT June 29, i.e. a half hour before the "fall of the Tunguska meteorite" [5].
No any "Tunguska meteorite" fragments were discovered. And many years ago it was proposed that the meteorite completely burn out into dust (even despite that it resembles a story about a snake which completely swallowed itself, commencing with its tail...). Recently the attempt was done to calculate the burn-out [7,17]. In the author opinion this attempt can't explain the absence of the fragments, because:
a)Even the results of [7,17] conclude that it must be a lot of small fragments a few kilometres from the epicenter. As already mentioned, despite many years of careful search - no one found. And no large quantity of extraterrestrial dust (droplets) was found in the epicentral area. The results of a search for globally dispersed the meteorite dust also are negative [18].
b)In [7,17] the opacity of the meteoroid dust and vapours are neglected [19]. It leads to overestimation of the ablation rate [19]. Below the author tries to demonstrate that the overestimation is very large.
In [7,17] it is proposed that the meteorite disintegrated due to aerodynamic loads and formed a swarm of fragments. The fragments are ablated due to radiation flux from the shock wave (an absorption is neglected) which envelopes the swarm. According to the calculations the average time of the fragment's burn out is about 0.1-0.2 s [17]. It is about the time, which takes the swarm of fragments to slow down to a speed at which the ablation disappears. So even despite the fact that in [7,17] the heat of ablation was taken 2 kJ/g - the minimum one, the conclusion about the burn out is "at the edge".
But now let's take into account absorption in the fragments. The fragments in the outer layers would shadow (screen) the inner ones from the radiation of the shock wave. If the radius of the meteorite before its disintegration was Rm =30 m [7], the radius of the swarm of the fragments is about Rs =200 m [7], the average radius of the fragments Rf =0.03 m [7], we can evaluate the absorption coefficient due to screening
k = PI * Rf^(2) * N,
where N is the average number of the fragments per volume. As the meteorite with radius Rm disintegrates into the swarm with radius Rs, it leads to
N = 3 * Rm^(3) / (4 * PI * Rf^(3) * Rs^(3)).
So the optical thickness of the swarm is (in a plane approximation, which can be used for the evaluation)
k * Rs = 3 * Rm^(3) / ( 4 * Rs^(2) * Rf).
For above-mentioned values the optical thickness is 17! Other words, the inner fragments are completely screened by the outer ones! If we also take into account the screening by the ablation's vapours, this conclusion become even much stronger. In [20] the optical properties of H-chondrite vapours were calculated. It is shown that the absorption coefficient k in vapours for the most intensive part of spectrum of the air-shock wave (at altitudes about 20 km) is in order of 100-1000 1/m. So in [20] it is concluded that taking into account the screening in vapours significantly decreases a rate of ablation for large meteorites. The author just can join this conclusion.
So the fragments in a swarm are practically completely screened, with the exception of the thin outer layer and the majority of the fragments must survive the entry.
V.A. Bronshten has come to similar conclusion (see: METEORITICS & PLANETARY SCIENCE, v.34, p.723 (1999)) with other arguments.
But as the author already has mentioned, no the fragments were discovered.
If you are interested in Tunguska geochemistry, then I would like to advise you to read this group of articles by Evgenii Kolesnikov with coauthors. Kolesnikov wrote many articles on "discovering Tunguska spacebody substance"
since late 1970s. Here is a link to an article by Rasmussen, Kaare L.;
Olsen, Hans J. F.; Gwozdz, Raymond; Kolesnikov, Euginev M.:
"Evidence for a very high carbon/iridium-ratio in the Tunguska impactor"
(
METEORITICS & PLANETARY SCIENCE, vol. 34, no. 6, pp. 891-895 (1999)).
But their results on composition of the "Tunguska spacebody" are
so unusual (if not strange), that it produced some argue by geochemistry's experts:
METEORITICS & PLANETARY SCIENCE, v.36, p.999-1006 (2001).
An Italian reseacher Prof. G.Longo also doubts in reality of these chemical anomalies writing in his article 'The Tunguska Event' (Comet/Asteroid Impacts and Human Society, An Interdisciplinary Approach (2007)):
So if even minor geochemical peculiarities possibly were detected in the "impact place" [16], there is no reason to claim them as of 'Tunguska spacebody', because of their composition. The latter one doesn't resemble a chondritic meteorite, neither a comet (as even pristine ice-rich cometary material is supposed to have a chondritic complement of about 50 wt% [18]).
I can add that the deuterium to hydrogen ratio (D/H) in the Tunguska "catastrophic" peat layer is less than in the adjacent ones (and, much less than in ocean water, of course), while the D/H ratio in all 3 researched comets (Halley, Hyakutake, and Hale-Bopp) is on contrary much larger than even in the adjacent peat layers.
Also isotopic ratio for Tunguska epicenter's rare Earth elements (REE) which was measured in the place of the most REE enrichment is the terrestrial one.
Regarding C-14, its data is rather contraversial, but the latest measurements seem to show no significant deviations against background.
And what about to propose that over the epicenter the
extraterrestrial substance was dispersed into fine microparticles
during the powerful Tunguska explosion and flew away, explaining why
there was no fall out? The answer is "hardly". For example, the latest
published calculations of the hypothetic Tunguska spacebody's explosion
show that a plasma column of the remnants was to strike the ground.
And as it is known. in the case of a powerful nuclear explosion
significant part of radioactive debris falls out not far from its
epicenter. So this scenario (99.999...% of the substance flew accurately
far away from the epicenter) looks very unlikely (impossible in reality).
But the problem is even much more deep. Where is enormous quantity
of extraterrestial substance, which the hypothetic Tunguska body was to
lose before its explosion? Indeed, according to practically all
calculations, the hypothetic Tunguska spacebody was to loose a
significant (probably even dominated) portion of its mass before it
reached the explosion altitude of 5-8 km. In other words, at least,
a hundred thousands tonns of extraterrestrial substance (from
large fragments to dust) would be deposited along the lower part of
Tunguska spacebody trajectory. Despite many years of careful search
nothing was discovered... By the way, a couple years ago application
of just one of the many Tunguska substance search's methods allowed
easily find small fragments of a meteorite (with initial mass of
several tonns, probably), which disintegrated over another place in
Siberia in 1904...
The absence of discernable nitrate excess (produced by the "Tunguska meteoroid" during its descent) is also a problem for the meteorite interpretation [18].
There is also some interesting ice-core data relating the year 1908. Here is from http://adsabs.harvard.edu/abs/2009arXiv0907.1067M
We estimate atmospheric chemistry changes from ionization for the 1908 Tunguska airburst event, finding agreement with nitrate enhancement in GISP2H and GISP2 ice cores, noting an unexplained accompanying ammonium spike. We then consider the candidate cometary impact at the onset of the Younger Dryas (YD). The estimated NOx production and O3 depletion are large, beyond accurate extrapolation, but the ice core peak is lower than predicted, possibly because of insufficient sampling resolution. Ammonium has been attributed to biomass burning, with a coincident nitrate spike found at YD onset in both GRIP and GISP2 ice cores. A similar result is well-resolved in Tunguska ice core data, but that forest fire was far too small to account for this. Direct input of ammonia from a comet into the atmosphere is adequate to explain ice core data at the YD event, but not Tunguska data. An analog of the Haber process with hydrogen contributed by cometary or surface water, atmospheric nitrogen, high temperatures, pressures, and the possible presence of catalytic iron from a comet could in principle produce ammonia, accounting for the peaks in both sets of ice core data.
For more you could read the whole article from the link above.
Here are my comments of the article.
- Authors accepted the speed of the Tunguska spacebody about 30 km/s. At such speed the spacebody unlikely to penetrate to low altitudes ~ 6 km unless it was exceptionally strong. But then it couldn't have been a comet!
- There is an interesting fragment in the article:
To compute an equivalent value from the simulation results, we sum the rate at the 75
degree North latitude band over 90 days following the event, which gives a net peak
enhancement value of about 1.50 x 10-6 kg m-2, in good agreement with the ice core
result.
...
Anyway even such 'loose' approach failed to fit the data with ammonium, so the authors wrote:
And finally, one more interesting fact. Chemically robust carbon particles
(probably diamonds) were found near the epicenter [21,22]. Their composition
leads to the conclusion of their terrestrial origin [21,22].
Here is a the from [22] (http://adsabs.harvard.edu/abs/1995Metic..30S.521H ):
The Tunguska impact event of 1908 caused the destruction of a large forested area but left no impact crater. It was interpreted to have exploded in mid-air and thus would disperse material in a fireball over a wide geographical area. Several attempts have been made to locate particles associated with the impact in materials such as tree resin (1) and even in Antarctic snow (2). One of us (JN) attended an expedition to the Tunguska impact area and collected samples of peat from a depth of 60 cm which is thought to be the level in the peat which holds the impact horizon and indeed contains charred vegetation. The peat was subjected to standard demineralization procedures using mineral and oxidizing acids to destroy all but the most resistant mineral phases. An emphasis was placed on the chromic acid treatment to remove organic carbon as the peat was inevitably of extremely high organic content but perchloric acid was also used to oxidize graphite. The residue after treatment has subsequently been examined using a scanning electron microscope (Jeol JSM-820I at 30kv) with a Kevex system to obtain an energy dispersion scan and subjected to stepped combustion to determine the carbon abundance and isotopic composition. The SEM revealed the predominance in the residue of chromium containing phases possibly as a result of the extensive chromic acid treatments but several very pure carbon-rich particles were also observed. These carbon particles were anhedral and up to 15 micrometers in size. Due to the nature of the acid treatment performed upon this sample only a very robust form of carbon could survive and the most likely mineral is diamond. Further analyses using a transmission electron microscope and selected are electron diffraction will be performed to resolve the true mineralogy of these carbon particles. Stepped heating experiments on the acid resistant residue in conjunction with static mass spectrometry (3) has been used to give both carbon and nitrogen contents as well as carbon and nitrogen isotope compositions. Carbon accounted for 0.6% by weight of the residue and was released between 550-650 degrees C with a delta^(13)C of -25 per mil. The nitrogen yield was 0.02% by weight of nitrogen released between 500-700 degrees C with a delta^(15)N of ca. 0 per mil. These represent terrestrial values and indicate that the carbon particles do not have an extraterrestrial signature. If indeed these carbon particles are diamond and related to the explosion of the Tunguska object then they may well have formed by a plasma process within the fireball (similar to CVD). Further refinements regarding the purification of acid resistant materials are in progress. References: [1] Ceccini S. et al. (1995) in Abstracts Presented to ESF Network on Impacts Meeting, Ancona, Italy, May 12-17, 1995. [2] Roccia R. et al. (1990) GSA Spec. Pap. 247, 189. [3] Wright I. P. and Pillinger C. T. (1989) USGS Bull., 1890, 9.
For more on the geochemical anomalies - see pos. 3.10.
Trees of the second post-explosion generation exhibited higher than normal growth rates in the woodland area devastated by the explosion [23]. In recent decades, the boundaries of the high growth rate zone were "drawing in" toward the eastern "trajectory". Here the frequency of genetic mutations among the young pine trees has increased 12-fold. Till now the meteorite interpretation doesn't explain it.
The unusual glow in the sky was first observed days before the event [23]. Beginning on June 23, 1908, atmospheric optical amonalies were observed in many places of Western Europe, the European part of Russia and Western Siberia. They gradually increased in intensity until June 29 and then reached a peak in the early morning of July 1st. These anomalies included an unprecedentedly active formation of mesospheric (noctilucent) clouds, bright "volcanic" twilights, disturbances in the normal motion of the Arago and Babinet neutral points, a possible increase in the emission of the night sky, and unprecedentedly intense and long solar halos. Later on, after July 1, these effects decreased exponentially [23]. The area involved in these phenomena was limited by the Yenisey river in the East, by the Tashkent - Stavropol - Sevastopol - Bordeaux line in the South, and by the Atlantic coast in the West [23].
It's very hard (practically impossible) to explain it even by the comet dust, because:
a) Nobody saw the comet. If it even existed it must be very small. When the Earth crossed a trail of the large spectacular Halley comet in 1910, it produced practically no effect.
b) For a few days the trail must cover all the Earth around. But the glow was localized in the Europe and the west Siberia in general. Moreover, there were no any reports of the glow in the event region, while the hypothesized cometary coma must be the most dense near its nucleous, i.e. affect the impact region the most.
c) Comet dust must stay in the atmosphere for many weeks, while 'light nights' disappeared in a few days.
d) The enormous quantity of extraterrestrial dust (to produce the prominent sunlight scatter) must strongly influence on the atmospheric absorption. But no unusually large absorption in the atmosphere was detected on the days of the glow (see section 3.12).
e) The sky glow was also observed at rather low latitudes, where it couldn't be originated by the scattering of the sunlight by the dust at night.
It is just a small part of the meteorite interpretation problems. The supporters of the meteorite interpretation usually try to ignore them. For example, when you are talking about the incompatibility between eyewitness's accounts and the meteorite interpretation, they use to say that the eyewitnesses often confuse and so on. But on the other side, the whole idea about the meteorite is based just on the eyewitness's accounts about flying fiery body!
All above-mentioned facts can be explained on the assumption that the Tunguska event was a terrestrial phenomenon, in which tectonic processes played a very large role. One of their manifestations is well-known - it is rupture and trembling of the ground, i.e. an earthquake. But now let's look at some others.
A surge in tectonic activity may produce various optical effects in the atmosphere: luminous columns, stripes, lightnings, flame, glowing sky, etc. Exploding "meteors" are among them.
Here is from http://abob.libs.uga.edu/bobk/ccc/cc042600.html :
...Rada has dug up a Chronicle of Aleppo (a major and very old city in Syria***) that was written down in 1926 - and the author had talked to an eyewitness of the great earthquake that had hit the city in August of 1822****). (Rada actually said August 1, 1821, but all sources I tracked down on the net say either August 13 or 23, 1822.) And what that witness has to say was really weird. From Rada's 'live' translation I got something like the following scenario:
- The witness was sitting in front of his house during a cool night.
- Suddenly the air got so hot that he couldn't breathe, and that
extreme heat lasted for some 20 minutes.
- Then he saw a bright light in the atmosphere that lit the whole
ground like sunshine. He describes the light like as if a "chamber
had opened in the sky."
- Next he heard a sort of great noise like thunder, and
- the air started to move left and right.
- Four shocks lifted him and others out of their seats, and they
were fearing for their lives, as if the sky would be falling.
- And then buildings all around them started to collapse, less than
30 seconds after the bright light had appeared, with the earthquake
and its aftershocks lasting for 40 days.
Here is how the onset of an earthquake at the Russian town of Kola began on February 21, 1873. The weather was calm. Suddenly it became dark and then an enormous fireball of a dark crimson color appeared in the eastern sky and vanished in the west. At this time underground jolt occurred and the earthquake began which lasted for 5 minutes. It was so strong that the houses swung and utensils fell.
Another interesting example. The "meteor" flew at low altitude in a blast of wind over the Russian town of Chembar past midnight on January 4, 1886, exploding on the road out of the town with loud thunderclap. This explosion killed a horse. Later the survived driver (coachman) just could tell that fiery serpent came flying and killed the horse. About 15 minutes after the explosion an earthquake struck the town.
These exploding fireballs happen in connection with many earthquakes. Some of them are mentioned in [24]. Here is an example.
During the earthquake in the Tama Hills, Japan June 17, 1931 "a fireball rose in the sky and disappeared. A sound like "Bah..." was heard. The lower sky was coloured pink-red for some time after the disappearance of the light".
The author thinks that everybody who are well aware of the eyewitness accounts near the Tunguska epicenter marks the similarity between these phenomena.
And one more very important observation proving that such luminous phenomena can be something more than just simple "lights". During the South Hyuga, Japan earthquake November 2, 1931 [24] a fishing boat called the "Ikedamaru" was engaged in fishing on the sea about 50 km off Utiumi, a town on the coast of Hyuganada. Near the time of the earthquake the boat began to pitch so heavily all of a sudden that the crew thought she was near being capsized. At the same time, to the crew's consternation, a large pillar of fire shot up from the surface of the sea near the boat.
During Matsushiro moderate earthquake's swarm in mid-1960s earthquake lights were pictured the first times. Below is a photo of stable glow (which lasted for 96 seconds) taken Sept.26, 1966 (from J.S.Derr: Earthquake Lights...// Bull. Seism. Soc. Amer., 1973, v.63, p.2177).
On April 22, 1974 immediately before the earthquake hit Kiangsu province in China, people saw a bright streak of light in the sky. Sparkling and glittering with the "lightnings" dancing across it, it proceeded from southwest to northeast. The spectacle went on for some 3-4 seconds. In another Chinese province, Liaoning, fiery columns and balls flashed up in the sky on February 4, 1975, and a "flame" shot up toward the sky at the time of the earthquake. The precursors of the Tangshang earthquake in the Chinese province of Hopeh on July 28, 1976, were revealing in a way. About a half hour before the disaster, a bright flickering light was spotted in the distance. Instantly it was transformed from red to silvery blue, and then lengthened into a blinding white strip that darted across the sky and went out immediately. The eyewitnesses had the impression of a nuclear explosion. At the time of the earthquake an engine driver saw a lightning in the form of 3 blinding light beams, which were followed by 3 mushroom-shaped smoke columns.
A very interesting luminous phenomenon was seen a night before aftershock M=5 of the 27 May, 1976 Lungling earthquake (China) [25]. Two Chinese seismologists observed a fireball about 50 metres in diameter 200 meters away. They watched the fireball for almost half an hour. Next morning at the fireball's site they found "an extensive remnant of a sand boil" [25]. Why not the Muong Nong type tektites production on mini-scale?
A great number of luminous phenomena was seen before the Sungpan-Pingwu (China) earthquake, August 1976 [25]. Columns, fans, balls and sheets were seen. Several Chinese seismologists observed on the evening July 21 a small fireball, which originated at the ground surface about 100 meters from where they stood. At first, it was about 1 meter in diameter. It then shot up to a height of 10 or 15 meters, whereupon the volume started shrinking, finally to ping-pong-ball size. After reaching the maximum height, the ball curved over in an arcuate trajectory, resembling a meteor and disappeared as it fell to the earth. The light would dim, then brighten again. Small wisps of white smoke swirled around the light, and a slight crackling sound was heard. A radio compass and telluric currents were unaffected. A small fuunnel-shaped hole in the ground was found at the place where the fireball appeared. In another case, a fireball started near a house, rose up along an arbor, and burned a hole in the roof of the house. A total of about 1000 fireballs were sighted, 50 in one evening. Chinese seismologists discovered that more fireballs occurred along intersections of river beds and faults [25].
In connection with the swarm of earthquakes in Quebec, Canada 1988-1989 a lot of lumonous phenomena were sighted: sparklings, dawn-like diffuse glow, aurora-like bands [26]. Fireballs a few meters in diameter often popped out of the ground in a repetitive manner at distances of up to only a few meters away from the observers. Others were seen several hundred meters up in the sky, stationary or moving. Some observers described dripping luminous droplets, rapidly disappearing a few meters under the stationary fireballs [26].
A very important results on the earthquake lights were recently obtained in relation with the 1995 Kobe earthquake. The investigation of the place where during the earthquake several "streaks of bluish-white color spread out for about a second" (for details see "Geophysical Research Letters v.25, p.2721 (1998)) revealed the traces of 1000 A electric current through the area of about 1000 sq. cm. (Dr. Y. Enomoto, personal communication (1998)).
Very interesting pictures of earthquakes lights and "their" burnt rocks preceding the 1999 Turkish earthquake can be seen here).
It is important also to add that there are some signs of a relation between regional lightning and shallow earthquakes (see "Geophysical Journal International" v.131, p.485 (1997)). Remarkably, that during 19th century an idea was popular that earthquakes are of electric origin!
In general "tectonic lights" could be "meteors", pillars, rays, shooting up flame (usually in an epicenter), semispheres, fireball, patches and bands (in the sky and on the ground), all-sky luminosity, flashes, "auroras", sparks, "clouds", black objects and many others. They have some tendency to move towards an epicenter of an earthquake. Also, please, pay attention, that sometimes earthquake lights accompanied very weak earthquakes.
As we saw, many of these "lights" display energy release, sometimes explosion-like character. Usually these events happen in connection (prior, at the time or after) with earthquakes. But sometimes (see below) the accompanied earthquakes are very weak and an energy release by explosive event exceeds an earthquake one. In the author's opinion [27, 28] these explosive events are arranged in large volume of medium (at first, solid state: rock, soil) and one of their the most remarkable features are explosion-like effects with manifestations often not localized in the vicinity of the epicenter (also see below). So the author proposed to name them nonlocal natural explosions (NNE) [27,28]. Also as they often look like an explosion of a flying luminous body, they also can be called as a geometeor).
Indeed, more and more data appears showing that geophysical medium (at first, soil, rock) is a complicated nonlinear active system possessing its own "memory". Such a medium is to be characterized by self-organizing and self-adjusting processes in it. Possibly that NNE are just one of the way of such self-organization [27]. Remarkably, that atmospheric processes play an important role in NNE, i.e. probably NNE is self-organization in/between two geospheres: solid Earth and atmosphere. The author has a little facts about a role of water, but preliminary it seems to be important too.
It is remarkable that NNE (as well as luminous phenomena) rather often occur at certain places and very seldom in others (it seems that such NNE-areas often don't coincide with areas of increased seismicity, but lie close to them).
Till now we don't know their physical mechanism. The author doubts that it could be explained just by electromagnetism, at least by known forms. Probably we must add something. Maybe just this self-organization? The author have an impression that NNE are just "the top of an iceberg" (one of the most clear manifestations) of some universal fundamental process (of self-organization?)[27,28].
Anyway, NNEs are real and, in general, probably, we can describe NNE events as a high-rate release of energy from a geophysical medium ( a solid state substance (soil, rock) is just the best example, probably), which manifests itself as mechanical and other actions not caused by direct mechanical influence of substance movement (ground oscillations). This definition has its shortcomings, but the author can't propose a much better one now.
In typical cases NNE looks like an appearence of luminous body (sometimes it could be dark and probably even invisible) which travels to some site (or originate at the site). Then it explodes (NNE itself takes place).
Unfortunately, a number of known high-energy NNE, which aren't connected with large earthquakes a rather small, so features of NNE are not well-known (for the latest development see my geophysical meteors article). Anyway, two properties are rather well-established already:
NNEs often resemble (look like) explosions of ball lightnings. So in many cases we could say that it was the explosion of the ball lightning endogenic (tectonic) origin. Who knows, maybe NNE could help better understand when and where better try to create artificial ball lightning in a laboratory?
When NNEs have a form of a high-speed ball-lightnings, they often resemble meteoroidal meteors (and confused with the latter ones). In such cases NNEs can be called "geophysical meteors" or just "geometeors" (see my www-article on geometeors).
In any case, NNEs exist, and could explain some famous hard-to-explain events.
Below are several NNE (geophysical meteors) examples. More of them are in my geophysical meteors article.
The 1991 Sasovo explosion was accompanied a by number of intriguing phenomena, sometimes resembling a (ball) lightning and even a tornado damage. There was some unusual and selective damage in the town and even in the village 20 km from epicenter. The azimuth distribution of hurled frozen soil from the crater and the damage has 4 lobes. But, on the other side, the small tree in about 10 m from the epicenter was undamaged. There were no damage on the ground level at distance up to about 1 km from the crater (only ground swing and jerking). At large distances there was unusual damage on the ground level and even water-pipes at distances up to 15 km from epicenter were torn off. During the explosion in closed and undamaged rooms in much cases different things flew with soft landings and even several persons were transported by unknown force. Hollow plastic toys and electric lamp bulbs exploded. At the distance about 10 km from the main crater two more pits in the ground appeared that night. Soil was hurled and there were accompanied light phenomena.
In the mid-1992 the second cratering explosion happened in sparsely populated area in about 8 km from the first one. The crater diameter was 11 m and depth was 4 m. In the crater soot-like film cover was present. Unfortunately, a little is known about the crater's appearance.
At the end of 1992 an instrumental research established the following. A decrease in the magnetic field reached 100 nT in the 1991 crater and 30 nT in the 1992 crater was recorded. The gravimetric survey with regard to a mass deficiency inside the craters indicated elevated values of gravity with fluctuating amplitudes up to 100-150 microGal for the 1991 crater and 100 microGal for the 1992 crater. Seismic monitoring for 2 weeks in the vicinity of Sasovo recorded not less then 2 small earthquakes endogenic origin.
An important fact: a tectonic fault passes through the area.
Here is a meteorological situation at the time of the 1991 Sasovo
explosion taken from NOAA-CIRES Climate Diagnostics Center ( the
data is interpolated, i.e. smoothed).
Comparing data for sea level airpressure of
April 11, 18 UT,
April 12, 0 UT, and
April 12, 6 UT,
the airpressure raise is clearly seen.
Cloudiness level also gradually raised (compare smoothed cloudiness's
data averaged for the following time intervals:
April 11, 18-24 UT,
April 12, 0-6 UT,
April 12, 6-12 UT,
April 12, 12-18 UT, and
April 12, 18-24 UT).
On the next day it increased further, as it can be seen on daily
averaged maps for
April 11,
April 12, and
April 13.
On March 29, at 4 a.m. (i.e. about midnight UT) the eyewitness suddenly felt a headache. He turned to the window, saw a flash of light, and heard "a clap". A formation in the form of straw-white-colored cylinder rose above the forest and flew into clouds. The air over the forest was filled with a smoke, and then it rained.
In the autumn a forest fall 30 m by 25 m size was found in a marshy area. The trees were uprooted there with its tops away the epicenter, forming a spiral with two branches. The rind of some trees was burned forming vertical stripes. The roots of trees were burned in a form of concentric bands. A part of the roots was charred from above and sometimes under rind (which, however, remained unaltered). The outer part of the spiral was characterized not only by burning trees, but also by concentric scorched circles around the standing trees.
In this region of Russia weak earthquakes (M~3) occurred from time to time pointing to some level of tectonic activity.
Meteorological situation was favorable for this geophysical event.
Atmospheric pressure dropped (compare smoothed data for
18 UT March 28,
0 UT March 29, and
6 UT March 29), while cloudiness
increased (compare smoothed data for
March 28,
March 29, and
March 30).
Interestingly, that detailed look at the cloudiness's development
reveals one more remarkable feature: there was a spike in the cloudiness
level right after the event (compare smoothed cloudiness's
data averaged for the following time intervals:
March 28, 18-24 UT, and
March 29, 0-6 UT).
The author is aware also of findings of unexplained radial (sometimes fan-like) forest-falls at different places of the world.
The extraordinary sequence of events made leading news items that evening and the following day. At first it was proposed that a giant meteorite fell in UK near Arthur's Table. But the following research didn't find any traces of the fall. Quietly, the item slipped from the news as it became apparent that the experts would be unable to find an explanation.
In [29] it is also mentioned that Arthur's Table is on Bala fault. The author discovered in [30] this earthquake. Its origin time was 20.38 UT and the position 52.7 N; 3.7 W. The depth was 33 km (i.e. uncertain) or 0 km. Totally it was recorded by 29 seismostations. One seismostation recorded dilatational first motion of seismic wave (i.e. motion toward epicenter), while a meteorite fall could produce only compressional (i.e. motion away from the epicenter) one.
Since that time several earthquakes were detected in the area.
Smoothed meteorological data shows airpressure rise at that time
(compare sea level airpressure for
18 UT, Jan.23, and
0 UT, Jan.24).
Also cloudiness level increased on the next day (compare smoothed
cloudiness data averaged for time intervals
January 23, 18-24 UT, and
January 24, 18-24 UT).
It was first described as an unidentified atmospheric explosion and sounded similar to the booms that have been heard in those years along the coast of Nova Scotia and New England.
It was a fairly fine day with just a light snow falling on Bell Island. A little bit later 11 a.m. local time a local resident saw a straight beam of white light coming down from the sky at a 45 degree angle to the ground. The glow was not strong, accompanied with a low noise and there was a strong thunderclap at the end of it. The thunderclap was heard more than 100 km away.
One witness said she heard 3 blasts and the ground shook with each blast. Another witness said that he heard another weaker blast a few hours after. The electric power in the houses went out just before the first explosion.
People on the mainland shore of Conception Bay reported seeing fireballs coming down out of the sky and hitting Bell Island. Four miles from Bell Island across open water, said there were streaks of super bright silvery bright light.
In result of the event one house was damaged, especially its electric devices. Nearby a small shed and electric transformer were struck also. Futher away a barn with attached henhouse were damaged. The henhouse was virtually destroyed, a wall smashed in and the roof torn off. Five hens were killed. Nearby 3 circular holes in the snow appeared, under the branches of a thin lir tree, which was scorched black about 5 feet high. A couple of other trees were also slightly scorched. The holes formed a triangle. The biggest hole was 4 feet deep and 3 feet wide. Fused material was present at bottoms of the holes.
All over Bell Island there was a momentary loss of electric power during the event, which soon has recovered, with the exception of a few houses in the vicinity of the incident.
Initially 2 main interpretations (a lightning strike and a meteorite fall) were put forward. At first local meteorologists confirmed that there was no thunderstorm activity in that area at the time, but it was snowing. But later the meteorologists have concluded that atmospheric conditions were in fact of a "thunderstorm nature" (to tell the truth, the author doesn't know what does it mean), so the idea about very powerful lightning (probably a ball lightning) became more popular, as no meteorite traces were discovered.
Remarkably that Bell Island contains one of the richest iron ore bodies in the world.
At 19.55 local time (09.55 UT) a red fireball was seen over the town of Dal`negorsk (appr. 44.5 N; 135.5 E), Russian Far East. It flew silently parallel to the ground surface with the speed of 15 m/s leaving no wake neither trail. After the fireball have passed the town, it 'dived' to the slope of the small mountain (the height 611m), then jumped up and down 6 times above the mountain surface. It was accompanied with a very bright light persisted for an hour. One eyewitness said that after it, the fireball took off and flew away.
The 'impact' site was researched 2 days after. The fireball destroyed about 2-3 cub. m of the rock. The site was covered with singed pieces of the rock with small metallic spherules sprinkled. At the edge of the site there was a burnt tree-stump.
Even in 1989 a strange 'field' existed in the site. Living organisms avoided the site. It negatively influenced on human health. Radio-electronic devices and photo-cameras used to malfunction in the site. For example, the photo-images often were absent while taken at the site, and when taken outside the site they were of good quality.
Three main types of remnants were found at the site. Pb-spherules (about 60 g.), Fe-spherules (about 15 g.) and 'sponge'.
The Pb-spherules consisted of Pb with a small percentage of other elements like rare-Earth ones. Dimensions - upto 4 mm.
The Fe-spherules were 2-4 mm in diametre and consisted of Fe with C and O and a small percentage of Cr, Co, W. The Fe-spherules were magnetized.
'Sponge' was a glass-like substance covered with a lot of 'holes'. Silicon 'threads' about 17 microns width with a gold 'thread' inside were discovered. The 'sponge' probably was remnants of rocks and the tree-stump in general.
The singed pieces of the rock were dehydrated and enriched in oxides of various metals. The silicon contents was slightly lowered.
The trajectory of the fireball was parallel of 2 faults and the 'impact' site was in the intersection of several faults.
In the evening (20.30 local time) of Febr. 8, 1986 two fireballs were seen near this mountain. They flew around the mountain 4 times and then flew away.
On the evening (about 22.40 local time) of Nov. 28, 1987 totally 32 fireballs flew over the Russian Far East region. Four of them flew over the mountain, three ones were above the town of Dal`negorsk and five ones illuminated environs.
Analysis by Soviet researchers revealed that the 'fireballs' tend to appear above faults and ore deposits during a full Moon.
First I would like to say that in the region some weak earthquakes occur from time to time.
And here is the meteorological situation for the Jan.29, 1986 event.At 23 hours local time (15 UT) a large orange red spherical "fireball" with a very small bluish white conical tail had flown from low down in the south over observers travelling to the north. Some observers reported that the fireball was cylindrical in form and more yellow-blue-white in colour. It was heard as a pulsed roaring or loud diesel engine sound - well before it arrived, it dropped off no glowing fragments, and had no long luminous tail or sparks - as is common meteor activity. Its speed was similar to a 747 jet liner or a fast jet plane.
No sonic booms were reported, and no observer believed that any explosion was heard until the "object" got to ground level - or very nearly so (behind low hills or tree line cover) - and exploded/or impacted.
It flew apparently parallel to the Earth's curvature in a long "nap of the Earth" arcing trajectory at low altitude (some 1-2000 metres ?) from low down on the southern horizon, not with a "normal" meteor inbound high angle high altitude trajectory. The fireball lit up some observers and their vicinity as it passed overhead. It's flight trajectory was observed over a distance of least 250 km. It then appeared to arc down towards the ground and disappeared out of sight behind trees or low hills.
This was followed after a 5-minutes delay by a near blinding massive high energy burst of blue-white light that rippled for about 3-5 seconds. It lit up the night (windless, cloudless, and moonless) sky as if daylight. The energy intensity involved in this light flash was similar to the light flash generated by a significant nuclear blast, and in many respects the incident strongly resembled a night time nuclear test.
A huge red coloured flare then shot vertically skywards for some considerable distance (several kilometres ?), and this was immediately followed by a massive seismic ground wave that hit the observers nearest to "ground zero" such that rocks and beer cans vibrated off of tables and the ground shook violently so that persons tending a camp fire fell over. At the small gold mine (the Alycia Mine) underground 7.5 cm steel pipes sheared clean in half and collapsed underground drives and shafts.
A very loud major explosive blast then followed that was heard over a 250 km by 150 km corridor, minor quake damage was reported as far as 150 km southeast of the "ground zero" - the other directions (excepting Leonora to the southwest) being largely uninhabited.
A large deep red-orange coloured hemisphere of opaque light with a silver outer shell lining then rose from ground level to hover around over the "ground zero location". This structure when fully developed was approximately three times the size of a typical Goldfields setting Moon as seen by observers located 30-50km from it - (i.e. it was very big), and it bobbed around a bit for nearly two hours, before disappearing suddenly.
This "half soup plate structure " (looking like a "deep red very large and half set Sun") was seen by two observers from widely separated locations, one at the Banjawarn station buildings, and one at the Deleta station buildings.
Almost exactly one hour after the first big event three observers (located at the Banjawarn station buildings) also saw a second much smaller fireball - more blue-green-white in colour, which appeared to rise from ground level (?), but which definitely rose from behind distant trees well south of the station perimeter, and flew to the north in a high mortar shell type arc before coming down to ground level, behind distant bush. It's flight path was divergent to the north northeast when compared to that of the first major "fireball" event of that night.
This later event then created a second but very small explosion and concomitant minor ground shake - similar to the first event, but much smaller in size, and with no resultant rising hemisphere of opaque light. This second event does not appear to have been of a magnitude sufficient to register on A.G.S.O. seismographs.
Next morning nothing unusual was seen from the hills nearby.
In 1995 H. Mason spent a considerable time in a airplane, but failed to find any crater or ground anomaly of any kind there or anywhere else in a 300 km diameter search area. Ground and air examination of the nearby Celia fault-lineament could find no evidence of any movement on this structure.
At about the same time H. Mason got a report by the three truckies seeing yet another fireball soon after starting work at 5.00 a.m. (exact date unknown) in May or June of 1993. Their "moon sized" fireball flew from south to north at low level (some 1000 metres) with a high speed jet plane velocity. It was yellow-orange-red in colour and had a very small blue-white tail, and lit up the early morning dark sky in an intense blue white light flash that silhouetted the countryside, as it too headed immediately west of Laverton directly for Banjawarn station. As they were sitting next to loud diesel engines of their own we do not know if this third Banjawarn fireball made any pulsed roaring noise. This third fireball held a course that, would pass over Banjawarn.
As H. Mason have informed the author, the 95% of eyewitnesses of luminous phenomena and seismic effects gave the epicenter at 121 deg 10 min East, 27 deg 05 min South. The distance from the Celia Lineament is 10-15 km on harmonic parallel linear. The rest 5% of eyewitnesses (just seismic effects) and the seismic monitoring network gave the epicenter a several dozens km to the south, right on the Celia Lineament, where it crosses with another fault. It is interesting to note, that the Laverton town water supply pumping station is quite close to the latter epicenter and there was a drought at that time, while several following years there was enormous flooding. In 1994 there were a few reports from the region of the "luminous epicenter" about strange 'explosive' sounds accompanied with minor seismic effects (in the author opinion - brontides, probably). Moreover, two other large orange-red hemisphere static light form structures have also been observed at night northwest of Banjawarn (in 1988 and in October 1992).
As the author found in the "Bull. of the Intern. Seismol. Centre", the focus depth of the earthquake was 1 km (according to H. Mason, the quake is calculated as negative in depth i.e. up in the air) and magnitude M=3.6, according to the Australian seismostations. One seismostation recorded compressional first wave motion, while another recorded the dilatational one ( this fact alone is enough to exclude a meteorite fall as a possible origin).
H. Mason takes into account 5 possible origin of the event. He admits
that is it unknown natural event, but, rejects 'earthquake lights', because,
as he writes "of their usually very low energy output". But as
he discovered strong correlation of this and other similar events in Australia
(see below) with geology (tectonic faults) and earthquakes, he is supposing
that the most probable it was the experiment with electromagnetic weapon
for inducing earthquakes conducted by Russians or Americans!
P.S. In August 2000 H. Mason e-mailed me asking to underline, that he has in
mind several possible origins of similar events, including natural ones.
Here the author would like to attract attention at one interesting aspect of the event. A surface explosion of about 500-1000 t TNT produces an earthquake of magnitude 3.6 (and a crater about 200 m in diameter). As no crater were found, it could be proposed that the explosion was aerial (if to ignore the given focal depth of 1 km), but it increases TNT equivalent at several orders of magnitude. But there were no reports or any signs of strongest air-shock waves produced by such powerful explosion. So we should conclude that the explosion and the seismic phenomena have another, much more tighter coupling mechanism than just shock-air waves (see also below).
The author have many arguments that the event was not such the weapon experiment and, of course, not a 'meteorite'(see: "Science News", June 7 (1997), p.359), but already known to us NNE, in some way a "powerful" kind of 'earthquake lights'.
Here is interpolated sea level air-pressure data for 27.5S, 121.25E (based on NOAA-CIRES Climate Diagnostics Center data):
1993, May 26, 12UT - 1025.2hPa
1993, May 26, 18UT - 1022.0
1993, May 27, 00UT - 1023.8
1993, May 27, 06UT - 1018.2
1993, May 27, 12UT - 1018.0
1993, May 27, 18UT - 1015.3
1993, May 28, 00UT - 1014.2
1993, May 28, 06UT - 1009.7
1993, May 28, 12UT - 1014.7
1993, May 28, 18UT - 1017.3
1993, May 29, 00UT - 1021.8
1993, May 29, 06UT - 1020.1
1993, May 29, 12UT - 1022.8
1993, May 29, 18UT - 1023.9
1993, May 30, 00UT - 1025.6
1993, May 30, 06UT - 1022.5
1993, May 30, 12UT - 1025.7
1993, May 30, 18UT - 1025.3
It is clearly seen that the event took place during a sharp air-pressure variations.
Recently I discovered this publication on the event. I think that the data presented could help you to evaluate a possibity of a 'meteorite fall' (some more info here: http://www.nsf.gov/news/news_summ.jsp?cntn_id=102814 , http://www.nytimes.com/1997/01/21/science/seismic-mystery-in-australia-quake-meteor-or-nuclear-blast.html?sec=health&&n;=Top/Reference/Times%20Topics/Subjects/M/Mines%20and%20Mining/Mining%20Disasters , http://adsabs.harvard.edu/abs/2002AGUSM.U22A..01H ).
At about 2 a.m. local time (18 h. UT, April 30) a large spherical orange-red fireball with a small conical blue-white tail was observed flying from the Indian Ocean over Bunbury in the Western Australia in a north northeasterly direction at a relatively high altitude, apparently flying a trajectory that was parallel to the earth's curvature. The altitude of this fireball is open to question as many observers thought that it was not too high in the sky but newspaper reports later placed it at several kilometres altitude.
The fireball soon arrived above the eastern side of the City of Perth, and was seen and heard by many eye-witnesses over it's 150 km land flight trajectory. Observers reported that the "object" emitted a loud roaring pulsed noise - similar to a diesel freight train - before it arrived - and that it flew at a steady speed similar to a high speed jet aircraft. There was no report of a sonic boom.
Whilst opposite the eastern side of Perth near Midland the fireball reportedly stopped dead in the sky and the tail inverted through the fireball to point towards the previous direction of travel.
There was then an enormous burst of blue-white arcing light energy that lit up the city and it's suburbs for many kilometres - briefly as clear as daylight - similar in many ways to that of a nuclear blast. A loud vibrating massive explosion cum seismic wave reverberated around Perth and the city buildings shook whilst books and objects fell off of shelves.
Several observers reported that at the instant of the explosion four white lights raced apart from the main "object's" centre forming a right angle white cross in the sky. No object was actually seen at any time - just a bright orange-red fireball of light emission and it's very small blue-white light conical tail.
One observer reportedly told the Perth Astronomical Observatory of seeing sparks drop off of the fireball during it's flight and that it had a long tail or streak of orange colour. All other Police and Public eye-witnesses reported the fireball as having no, or at best a rudimentary very short, tail, and they definitely saw no sparks, noting that it was spherical or cylindrical in form as defined by light energy emission.
About half of the city's population was woken up by the violence of this explosive and seismic wave event. The ground vibration wave was picked up by the A.G.S.O. Mundaring Seismic observatory as a paper analogue recording lasting some two minutes timed at 17.57 UT i.e. commencing at 1.57 a.m. local time.
This event raised some discussion in the press over the next few weeks and was generally explained in the media by the Perth Astronomical Observatory as the explosion of a meteor fireball with a power of one or more mega-tonnes of TNT equivalent, at an altitude of several (20 km ?) kilometres. Surprisingly this event was not apparently widely reported in the World press.
Reports soon came in of small lights and strange aerial noises that had moved to the north northeast of Perth towards the small town of Toodyay (about 70 km to the north-east of Perth) and beyond, on the night in question. Amateur meteor astronomers spent a considerable amount of time interviewing farmers out that way but no meteor fragments have been recovered at least to the date when H. Mason was writing the article [31], i.e. December 1996.
Later reports noted that on the same night, some 1900 km to the north- north east of Perth, a couple situated on Sunday Island, north of Broome, in the Kimberley region of the Western Australia, were woken some time around 3.00 a.m. local time by a loud roaring pulsed diesel engine noise - similar to a D9 bulldozer or tank engine - advancing directly towards their front door. This noise rose to a crescendo and books and objects fell from their shelves. The seismic ground vibration wave and sound event lasted for some 1-2 minutes. Believing they had experienced an earthquake the family listened to the early morning ABC radio, but the only story was of the explosive meteor fireball event above Perth. A check of the Mundaring seismic records has shown that no earthquakes of any magnitude at all occurred at Sunday Island or anywhere else in their region that night.
And again H. Mason inclines to think that it was electromagnetic weapon experiment! The author don't touch here his idea, just marks, why hardly it could be a meteorite.
1) Its flight and trajectory don't conform the meteoritic one.
2) It didn't look like a meteorite.
3) Its roaring sound and absence of sonic boom are hard to explain by a meteorite fall.
4) Its explosion looked like an explosion of a ball lightning, but not a meteorite.
5) Let's compare the seismic effects of its explosion with the seismic effects of the explosion of the real St-Robert meteorite June 15, 1994 near Montreal, Canada [32]. During this meteorite explosion at 36-33 km height, its mass was about 1200 kg, and it transferred to the acoustical energy equivalent of about 500 t TNT. Windows rattled, and skyscrapers swung, but the amplitude of the ground vibrations was very small - just 4 nm [32]! Other words, the above-mentioned 'seismic' effects were produced by air waves, not by a quaking of the ground. The characteristic 'sign' of air wave actions on buildings - the superiority of 'external' disturbance over 'internal' quaking. It means, for example, that windows could rattle and be broken, but bottles in a refrigerator don't fell. A good example of the air-wave action is the destructions in a settlement 400 km away (a region of a focus of blast air-waves reflected from the ionosphere) from the 1961 Soviet 58 Mgt nuclear blast at 4 km height. Wood houses were destroyed, at stone ones roofs, doors and windows were absent (blown away).
In the Perth event we see considerable 'internal' seismic effects, with no report on 'external' damage ( mass broken windows, roofs etc.). So it could be stated that there was another origin of seismic effects besides air-waves, as well as at the 1993 Banjawarn event.
6) After the explosion of the St-Robert meteorite at 36-33 km height more than 25 kg of its 1200 kg mass were found [32]. But as the hypothetical Perth meteorite is expected (from the comparison of the explosions energies) to be hundreds-thousands times larger and the explosion height even lower, the absence of any recovered debris looks very astonishing.
7) It is very remarkable that the Perth fireball whole 150 km long land flight trajectory and the explosion site are exactly over the Darling tectonic fault, where small earthquakes occur from time-to-time (in H. Mason's opinion, there was a small 10 degrees difference, as he e-mailed me in August 2000) .
As a conclusion, it could be stated that the 1995 Perth event reveals many signs of NNE.
Here is sea level air-pressure interpolated for the Perth's area (based on NOAA-CIRES Climate Diagnostics Center data):
1995, April 28, 18UT - 1016.3hPa
1995, April 29, 00UT - 1018.2
1995, April 29, 06UT - 1017.0
1995, April 29, 12UT - 1018.6
1995, April 29, 18UT - 1019.4
1995, April 30, 00UT - 1020.7
1995, April 30, 06UT - 1019.2
1995, April 30, 12UT - 1019.4
1995, April 30, 18UT - 1020.5
1995, May 1, 00UT - 1022.3
1995, May 1, 06UT - 1022.4
1995, May 1, 12UT - 1025.2
1995, May 1, 18UT - 1027.3
1995, May 2, 00UT - 1030.7
1995, May 2, 06UT - 1029.7
1995, May 2, 12UT - 1030.7
1995, May 2, 18UT - 1031.4
It is seen that the event took place during atmospheric pressure jump.
A bolide was seen (and a sky was very bright) followed by a huge electric discharge and also some seismographic records. The event happened in Poland near Cracow (Babia Skala, Jerzmanowice) on January 14, 1993. A good part of the "Babia Skala" limestone crag was thrown to distances of over 200 m, and the largest piece was of more than 100 kg (80 m apart from the stroke). Sinuous or zigzagging furrows radiating away and bifurcating were carved in the grass-cover soil surface within 50 m from the detachment point on the crag. Electric wiring in the village was melted.
This event was connected with three discharges, which were practically straight-line discharges. The first one was the largest (at 17h 58min 53.9s UT, timing from the seismic records), and proved to be about 17 degrees (+- 10 degrees) inclined to horizon, very shallow. It started at a height of 2.05 km (+-065 km), longitude 19,693 +-0.014 deg, latitude 50.183 +-0.004 deg, and terminated exactly at longitude 19.756 deg, latitude 50.207, height 0.48 km. It was 5.5 +-1.2 km long. The second discharge happened at 18h 00min 16.4s UT and the third one at 18h 01min 43.3s UT.
The author can add that the site of the event is the site where weak small-focus-depth earthquakes happen from time-to-time and a cold front (which was passing the area) is also favourable for 'earthquake lights' activity.
In the clear dawn of January 18, 1994 a bit before 7h 15min UT many people in Santiago de Compostela witnessed a very bright luminous object crossing the sky in a descending trajectory (according to some reports, at a certain point of the trajectory the descent changed to a sharp fall). It was described as a fireball with a small red-orange tail with apparent angular size. A surface crater in Cando (8.864 deg. W, 42.843 deg. N) with dimensions 29 m by 13 m and 1.5 deep was later discovered near the projected "impact" point of the luminous object. At this side, in addition to the topsoil, full-grown pine trees more than 20 meters high were thrown downhill over 90 m away. No meteorites were discovered.
Meteorological conditions were favourable for geometeors. There was an airpressure upsurge (compare smoothed data for sea level airpressure for January 18 6 UT, and 12 UT). Also cloudiness level increased several hours after the event. You can see it in smoothed and averaged cloudiness's data for the following time intervals: January 18 0-6 UT, 6-12 UT, 18-24 UT, and Jan.19 0-6 UT.
The author can add that the site of the event is the site where weak small focus depth earthquakes happen from time-to-time.
In the clear evening of Nov.22, 1996 at the large area of the Western Honduras there were a lot of luminous phenomena, accompanied by sounds and ground trembling. Immediately after the event the Moon became dark and the night became foggy/cloudy. Some people reported smelling sulfur. Also at some places coffee plants faded away, the water became bad, many people became ill, some fissures were discovered on the ground, several landslides took place at about these times.
Here are some examples of the luminous phenomena: very bright fireball followed by loud concussions 2-3 seconds later; the sky split and fire came down; bright diffuse light; string of pearls; a group of stars crossing the sky; a rotating object with curved trajectory; an object moving in zigzag; a red clearness.
A remarkable phenomenon took place in El Progresso town about 8 hours before the event. A small stone fell on the ground. The stone was retrieved from the yard while still warm. It was spinning and de-gassing (with strong smell of sulfur) after digging itself into a small crater. The stone was red-hot, about 4 cm in diameter, and turn black on cooling. After a few days the fragment had disintegrated into gray ash. Approximately 2 minutes before the fall a bright fireball was seen high in the sky. The author would like to attract attention to this phenomenon, because it resembles (in smaller scale) some Evenks accounts of stone falling at the Tunguska times. They resemble the famous (and still unexplained) 1855 Igast episode ( see "Nature" v.209, p.67 (1966)) and some others.
Several international expeditions searched for the meteorites, but no meteorites were discovered.
Besides a connection with the weather change, the author would like to attract attention also to a remarkable coincidence of the event with solar activity. While the solar activity was very low at that period in average, there was a short-term upsurge of it right at the time of the event.
It took place at about 55.4 N, 77.5 N on June 27. The sky turned black, thunders and lightnings struck. Through the clouds came the fireball. It disappeared behind the horizon, then the fireball struck with a loud bang and flash. The hunters were the closest witnesses to the impact of the fireball. When they returned home, a new bay had been carved out of the shoreline. The whole area affected had about a quarter-mile radius. Geologists proposed that it was just a landslide of the shore. But it didn't conform with the debris found 3 miles out on an ice floe, and a bus-sized crater discovered in the water. Moreover, soon reports appeared about fireballs at other dates. For exapmle, a fireball was seen speeding towards the site in the evening June 22. There were also reports of 2 separate tremours at the time. A seismic station 210 km away recorded a disturbance in the evening of June 22. Geologists were stumped by the cause of the tremours, but said weather is probably responsible. In total, fireballs were seen on 4 different days: June 22, 24, 27 and July 4. Some local residents said that similar event took place in years gone by. As usually after large initial interest (a large meteorite fall!), it is now almost forgotten, as many other events, which don't conform popular explanations (a meteorite fall, a landslide, etc).
For more info, below is a part of an e-mail, which Alex Roslin sent me:
Geophysical situation was favorable for NNE (geometeor).
Besides coincided "thunders and lightnings", there was airpressure
fall on that day (compare sea level airpressure data for
June 27, 1997
12 UT,
18 UT, and for June 28
0 UT, and
6 UT).
Also compare GOES-8 infrared picture of the area taken
12:15 UT, June 27, and
00:15 UT, June 28 i.e. right after the event.
A tremendous development of cloud's cover in the area is clearly seen.
THE AUGUST 3, 1963 "ALMOST TUNGUSKA" near South Africa.
To finish the examination of certain NNE (geometeor) events, the author would like to mention that anomalous sounds, described as gun shots etc. and sometimes accompanied by small tremors are well-known from many places of the world (including the West Australia, where they were heard, for example, on June 26, 1908 [33]). They are usually called "Barisal guns" or "brontides" [34] and, as a rule, are reported to be heard at the places of increased tectonic activity (which often doesn't manifest itself through strong earthquakes). Sometimes strong whirlwinds and other forms of wind actions appear with these sounds. Some authors incline to think that the sounds precede a bad weather. There is a report that the site where these sounds used to come from resembled a site which was struck many times by lightnings. The author thinks that brontides are caused by NNE (recently he was surprised to discover that as long ago as in 1896 the proposal was published that Barisal guns and other natural booming sounds are likely due to ball lightning explosions!).
Till the end of the 18-th century the general scientific opinion was that all fireballs are terrestrial origin. Soon after the pendulum swung in the opposite direction. In the author opinion, the truth is, as usually, in-between.
You can read about more fresh NNE-events in Tunguska-related news and in geophysical meteor article.
Let's return to the 1908 Tunguska.
Now the author try to demonstrate that the increase of tectonic activity is expected at the site and the time of the Tunguska.
At first, the Tunguska occurred the place of the most powerful volcanic
activity in the Earth history 250 millions years ago. The Tunguska explosion
epicenter is right in the middle of the ancient volcanic crater, which
after its discovery in 1972 got the name "Kulikovskii". This
volcano is a part of Khushminskii tectono-volcanic complex [35].
You can see this with your eyes below. Here is a satellite photo (as I
understand, probably in near-infrared band) of Tunguska epicenter (from
www.adbelkin.boom.ru/tunguska/infr-cn-tung.jpg). In there a "star" marks
the epicenter. Pay attention to bean-like Lake Cheko (the largest dimension
is 700 m) about 8 km to the NNW of the epicenter.
There are many prominent tectonic faults, circular structures and other geological formations in the region (see FIGURE1). Many of these tectonic faults are no older than of the Neogene age [38]. Several prominent tectonic faults are intersecting near the Tunguska explosion epicenter.
The southern border of the Tunguska event manifestation is the Lake Baikal rift. This rift is a place of high tectonic and seismic activity.
At least, during last century and at the beginning of 20-th, there were many reports about seismic activity in the middle of the Tunguska event region (about the latitude of Kirensk town) [39]. The author also found a couple reports about earthquakes from the northern part of the Tunguska event region in the middle of 19-th century [5].
There are signs of increased tectonic activity during the time of the Tunguska. For example, in 1908 ten observer's reports on seismic events came from the Lake Baikal region. In the next few years, their number dwindled abruptly (1 - in 1909, 2 - in 1910), no shocks having been registered in 1911 [39].
The distribution of the reports on seismic events inside the year 1908 is also remarkable. On FIGURE2 there are the reports on earthquakes in the Lake Baikal region from the spring to the fall of 1908 [39].
It is seen that the seismic events are concentrated near the Tunguska date, June 30. It is also notable to mention the July 1908 message by the Tomsk's student Bryukhanov A. to the director of the Irkutsk magnetic-meteorological observatory, in which Bryukhanov wrote about unusual event near Ust'-Kut settlement (513 km, 152) - the appearance in the 1908 summer of a hot spring with various chemical elements presented. It didn't exist before.
So there are evidences of the activation of tectonic processes at the place and at the time of the Tunguska.
Moreover the author's analysis reveals activation of tectonic processes at the Tunguska times not only in the Lake Baikal rift and the southern part of the Siberian platform but also on more large (global?) scale. The evidences are following.
June 23 - 9
June 24 - 10
June 25 - 7
June 26 - 7
June 27 - 4
June 28 - 7
June 29 - 6
June 30 - 17
July 1 - 17
July 2 - 7
July 3 - 10
July 4 - 3
July 5 - 6
July 6 - 8
July 7 - 7
So there are evidences of the large scale (global?) disturbances in the Earth interior in 1908 which culminated at about the Tunguska time.
There are also some other evidences of the extreme geophysical situation at the time of the Tunguska. On June 29 the 'Alps Glow' phenomenon was registered in Austria [46]. Remarkably, it was the only registration of this phenomenon for the whole 1908 summer [46]! Interestingly, that the exceptional sky glow (aurora?) was observed by the Sir Douglas Mawson expedition in the Antarctic just 7 hours before Tunguska [47]. In the expedition papers this glow was described as "The most extensive glow aurora seen on trip" [47]. Curiously, the global geomagnetic activity on these days was rather low [46], so the geomagnetic conditions were against the auroral activity. The only geomagnetic disturbances known to the author were unusual character and were registered in Kiel, Germany [48]. The disturbances occurred every evening June 27-30 for about 7 hours and had the period of 3 minutes. They were not ascribable to any recognized cause [48].
There was a report on disturbances of telegraph lines near Prague at about June 30 [49].
A very powerful (gas?) explosion occurred on July 1 at Makar'evskii mine (not far from the town of Taganrog, Russia) with catastrophic results and on this day the Geophysical observatory near S-Petersburg rcgistered strong air-pressure disturbances.
It is important to note that on June 30 the appearance of a rather large solar protuberance was discovered [46]. I also suspect powerful solar proton event in the late of June, 1908.
There were also some peculiarities in global atmospheric circulation at about the Tunguska date. In June 1908 a high barometric maximum was lying in the north (the Arctic region), and the winds were blowing from the north [49,50]. Cyclones over the Siberia in June were much deeper than usual, it led to significant increase of air pressure gradients [51] (it could also lead to activation of tectonic processes). Another peculiarity was a unusual warm (hot) weather over the Europe and, especially, Siberia in the second half of June. Together with the small number of thunderstorms it led to drought in some regions.
At the beginning of July the situation sharply changed. There was a strong increase in thunderstorm activity. Powerful thunderstorms took place [51,52]. For, example in the Perm' province, Russia in July a quantity of precipitation was a record for the whole 70 previous years of measurements. The northern (Arctic) area of high pressure sharply decreased in dimensions [51].
Remarkably, that an Greenland ice layer corresponding to the spring-summer of 1908 contains extremely large quantity of terrestrial dust (probably soot, in general)!
The author also would like to emphasize that notes of the Tunguska region meteorological stations reveal that it was a change from good weather to a bad weather right on June 30, 1908 (expecially on the morning). Recently the author discovered that in late 1920-s while discussing the Tunguska in Soviet Academy of Science outstanding Soviet meteorologist Prof. Mul'tanovskii B. attracted attention on a possibility of cyclonic air mass movement activation at the place and the date of the Tunguska!
The recent research by the author reveals that Tunguska took place during
strong meteorological anomaly on the regional level, in particular it exactly
coincides with a powerful peak of the atmospheric pressure upsurge.
Here are some details below.
Recently I have ended a research of a cloudness level in association with Tunguska. A reason was an empirical fact that the NNE (geometeors) have a tendency to occur on the eve of cloudiness upsurge (also it is known that sometimes before an earthquake a cloudiness is decreased in an epicentral area ). For geometeors you can see a graph of cloudiness (for details see my geophysical meteors www-article).
So I have found data of 9 meteorological stations situated no far than 1000 km from the Tunguska epicenter (the closest was 500 km away). I have averaged the data between the stations for better statistics. And indeed, Tunguska was in 'lacuna' in cloudiness, and the averaged daily cloudness level shows strong increase of cloudiness after Tunguska! You can see it on the graphic below.
And one more meteorological peculiarity of the Tunguska. It is thought by
seismologists that atmospheric pressure variations can trigger
earthquakes.
And geometeors have some tendency to occur during atmospheric pressure
variations (especially during its peaks) - see this
picture (for details see
my geophysical meteors www-article)
So I used the data of 9 meteorological stations situated no far than
1000 km from the Tunguska epicenter (the closest is 500 km away). I have
averaged the data between the stations for better statistics. And indeed,
the time of the Tunguska was right at the time of a maximum of atmospheric
pressure strong upsurge. In the best way it is seen from the data of the
Irkutsk station, which had a sampling rate every 3 hours. And the maximum of
the air-pressure upsurge was between 6 and 9 a.m. local time (UT + 6h.57min.),
while the Tunguska explosion was a little bit later 7 a.m.!
You can see it on the graphic below, where the time of Tunguska is marked
with a vertical line.
Unfortunately, a little known on meteorological data right in the Tunguska
epicenter. While in the closest to the epicenter places witnesses
(Evenks) said about a clear weather at the time of the Tunguska event,
in some others (typically a little bit far away), they said that weather
was not so good. Here are several interesting accounts below. Also,
please, pay attention to remarkable "red color" and that sequences of
the phenomena don't conform with a meteorite explosion).
- Nastya Genkoul'(river Khushma (somewhere ~32km, ~125)). There was a
good weather,
then suddenly it rained, strong wind commenced. Trees were uprooted.
- Aksenova O. (upper reaches of the Mutorai river (54 km, 244)). There
was a good weather on the early morning. Then wind commenced. It became
dark, as before a rain. The ground got red color, and a strong thunder
struck. She did not see anything on the sky.
- Andreeva E. Ya. (upper reaches of the Severnaya Chunya river (137km,
84)). There was a windstorm in the morning, then there was a strong
thunder, and the ground shook. After the thunder, the sky got red color
towards Vanavara.
- Dmitrieva M.V. (a little bit to the north of the mouth of Kimchu river
(96 km, 305)). On the early morning the weather not not rainy, but gloomy.
The sky was covered with high clouds. No wind. Then there were
"explosions", a strong wind, and an earthquake at once. Also after the
explosions, the sky got red color, and then the red color gradually moved
to the west.
The closest to the Tunguska epicenter Kezhma meteorological station (214 km, 193) registered at 9 pm local time on June 29 cloudiness 3. At 7 am local time June 30 (i.e. at about the time of the Tunguska) cloudiness was 4, and at 1 pm local time June 30 (i.e just less than 6 hours after Tunguska) - cloudiness was 10, i.e. maximum! Also at 2 pm local time a thunderstorm with hail occured between Kirensk (491 km, 131) and Nizshne-Karelinskoye (465 km, 133) settlement (but closer to Kirensk).
Conducted by Dyomin, Dmitriev, and Zhuravlev [1984] statistical analysis of witness's accounts revealed that Tunguska event was accompanied with various meteorological phenomena, including strong wind (windstorms), haze, fog, temperature changes, thunderstorms, whirlwinds.
In other words Tunguska indeed took place during a strong meteorological anomaly, as the tectonic Tunguska interpretation predicts!
It is interesting, how supporters of meteorite/comet fall explain the facts. As just accidental coincidences? But aren't too many the "accidental coincidences"?
As a conclusion, it could be stated that at about the date of the Tunguska there was the large-scale (global?) as well as local (Tunguskan) disturbance of geophysical situation, including activation of the tectonic processes.
The simplified form of proposed scenario of the 1908 Tunguska event is following.
The large-scale (global?) geophysical disturbances of late June 1908 (see section 3.4) manifested as the activation of the tectonic processes in the southern part of the Siberian platform and in the Lake Baikal rift. On June 30, at the time of large-scale weather worsening, the activation coupled with meteorological activity revealed itself in the most bright form - the Tunguska event.
The first phase of the Tunguska began with the appearances in the
atmosphere over the southern part of the Siberian platform (and possibly in
adjacent regions) of luminous phenomena. Some of them were bolide-like and
being mistaken for a bright bolide (meteorite fall). In general, they
appeared above tectonic faults, circular structures, etc.. At about the
same time, a swarm of (apparently shallow) earthquakes commenced, accompanied
by brontides.
At the vent of the Kulikovskii paleovolcano, the coupling between
tectonic and atmospheric processes manifested in a spectacular explosion-like
form. In general the seismic and other phenomena probably lasted for several
hours from place to place.
Unfortunately physical mechanisms of many of the above-mentioned processes are still unknown. But there are numerous hints that probably terrestrial electricity (electromagnetic procceses) play a large role. Anyway their manifestations on much smaller scales are known.
Below, the author tries to demonstrate, how the tectonic interpretation can explain the phenomena, which the meteorite one fails to explain.
The luminous phenomena of the Tunguska are in the stream of the "tectonic lights" (see sections 3.1, 3.3). So now just let explain the existence of the "three trajectories of the Tunguska meteorite fall". If we look at the tectonic map of the region (see FIGURE1) we could see that all three trajectories are above the main tectonic faults of the region. The eastern trajectory superimposes on the Beryozovsko-Vanavarskii fault, the south-eastern projects on the Norilsk-Markovskii fault, and the southern trajectory is over the Angaro-Khetskii fault and partly Angaro-Viluiskii fault. They intersect inside the Vanavara circle structure.
Interestingly, at first, it was thought that the meteorite fell at this intersection site, because local Evenks told about a forest fall, fire and a disintegration of a hill (cliff) in this region. Also there were reports about an appearance of unusual pits in the ground at this region. But, unfortunately, the first research in the area was conducted just in 1960-s and didn't produce definite conclusion.
The other places whence reports came about some manifestation of the Tunguska also happen to lie near major geologic features, like the Chadobedsko-Irkineevskii fault and the Chadobedskaya circle structure in the southwestern sector, for example.
The low heights of luminous phenomena explain why there where different accounts from the same settlement, and why practically nobody saw the fireball close to the epicenter, as at Vanavara, for example. The several lightning-like explosions at the epicentre, reported by the Evenks are in a good agreement with the typical series of 3-4 explosions during the Barisal guns events (see section 3.3).
According to the tectonic interpretation, there could be the following causes of the forest fall (probably they combined):
Early the author already mentioned unexpected strong wind accompanied the 1886 Chembar event and whirlwinds, accompanying the Barisal guns events. Here are examples of winds connected with earthquakes, taken from the author's collection and from [53].
One of the first cases was referred by the great French physicist Arago F., that on July 5, 1582 in Germany the earthquake produced a strong windstorm.
Of course, some of the occurrences maybe just coincidental, but in the others the probability of accidental coincidence seems to be very small. The analysis of 490 earthquakes [54] revealed that a few percent of them were accompanied with different forms of wind action.
It is interesting to note that the Tunguska forest damage resembles a damage caused by so called a downburst (a strong downdraft of the atmospheric air). Moreover, the Tunguska meteorological conditions hint on their some possible resemblance with those favorable for 'dry downburst'. Maybe a downburst, or several of them triggered or even driven by the tectonic processes (for example, by heating the atmospheric lower layer, by an increase of the atmospheric electric field, by degassing etc.) played a large role in the formation of the Tunguska forest-fall?
According to Zotkin, Nikolaev, and Peskov [2000] experiments with 26 trees in the epicenter of Tunguska event have estimated an average wind speed to uproot a tree in the epicenter's area as low as of 26 m/s (the rather low value is probably due to a shallowness of trees roots in the area). For comparasion, a wind speed in a meteorological downburst can easy attain much larger values. It is also remarkable, that the Chuvar forest-fall resembles the one produced by a powerful inclined downdraft - so called "burst swath".And one more interesting detail. As above-mentioned, the great percentage of the survived trees have lightning or lightning-like damage (also see below). But sometimes lightning strikes could be accompanied by blasts of hot air [55]!
Now a few words about the rotation of the fallen trees in the Tunguska epicenter (see section 2.2). A rotation of various objects in epicenter areas of many earthquakes is well-known. For example, in the epicenter of the 1966 Tashkent, USSR earthquake the rotation was about 10-20 degrees. At some earthquakes the rotation achieved 180 degrees. Probably, the most intriguing rotation is known during the 1822 Valparaiso, Chile earthquake, where 3 standing close to each other palm-trees turned around each other like a screw. Also, it could be mention that ball lightning explosions can produce some torque. Moreover Dr. Alfred J. Bedard Jr. of NOAA/Environmental Technology Lab. confirmed to the author that some downbursts indeed produce a rotation.
According to the tectonic interpretation there could be 2 general sources of the trees burn: the light (including infrared and ultraviolet) radiation from the explosive source(s) and electric currents generated by it (them). The burn by the electric currents could explain the 'lightning-like' tree damage, the burn at the site of the branch break (see section 2.3) and the spot-like character of this burn. Please, also pay attention that the electric discharges could be responsible for the thermoluminescence anomaly in the epicenter.
Anyway, cases of burn in connections with earthquakes are known. For example, during the 1693 Sicilian earthquake, the small town of Millitello was suddenly plunged into an unusual mist, and a loud explosion was heard. After the disaster, the ruins of the town and its environs showed traces of burn, while the vines in the surrounding countryside looked scorched. More recently, in 1988, bushes were burnt in places in the area of a tectonic fracture on the site of the earthquake in Spitak, Armenia. See also sections 3.1, 3.3.
If we look at the map of the tectonic faults at the region, we could see, that the reports on seismic phenomena came from the areas close to tectonic faults and circular structures. Especially strong the seismic phenomena were along the Angaro-Khetskii fault and the southern part of the Angaro-Viluiskii fault. The Angaro-Khetskii fault is also a part of the Trans-Aziatskii lineament, which crosses the whole Siberian platform. The increased number of sky glows (auroras?) was detected over it.
So, besides the main seismic source at the Tunguska epicenter, there were probably a lot of weaker sources in those areas. Some of them were strong enough even to affect the nearest Irkutsk seismograph and to prolongate the recording. Probably, the sources were of the small focal depths.
In [16] it was recognized that the composition of the discovered microparticles resembles the traces of increased tectonic activity or volcanic activity. But authors of [16] were not aware of the increase of the tectonic activity at the Tunguska site and time (see section 3.4).
The author also states that discovered chemical anomalies are very similar with accompanying tectonic and volcanic activity. The author compared them with microparticles from the Kamchatka volcanoes and found that their morphology and even dimensions are also similar.
Iridium is also revealed in the volcanic emanations, especially from the "hot-spot" regions [56].
Discovered isotopic anomalies at the Tunguska epicenter also conform the tectonic activity.
One more remarkable fact: there is a large ore deposits of platinoids (including Ir) about 1200 km to the north of Tunguska epicenter.
Besides volcanic (tectonic) degassing/emanation, it is also important to mention that there are some evidences that some substance could be brought by the luminous objects, at least, sometimes.
The author can refer to the work [57]. In there it was discovered the increased number of chromosome mutation in seismically active regions. It is also known that electricity (remember its probable role in Tunguska!) accelerates a tree's growth.
And the another interesting effect, possibly having relation to some anomalous manifestations of the Tunguska. At a half an hour before the 1988 Spitak earthquake (Armenia, USSR) the launched at Yerevan city ballooned cosmic rays counter began to register the increase of counts unusual character [58].
It is interesting also to note, that at many trees from the Tunguska epicenter the lignification of the 1907 tree rings wasn't completed to the time of the Tunguska [59]. It looks strange from the meteorite point of view. But from the tectonic interpretation, it is well-known, that before earthquakes a plants are affected sometimes, with a tendency to a negative influence.
As we saw, the meteoritic interpretation doesn't explain the sky glow. So it can be proposed that the Tunguska and the sky glow are independent and their coincidence is pure accidental. It is possible, despite the impression amongst many scientists that they are somehow related.
The tectonic interpretation admits that probably they are just different manifestations of the same geophysical processes. The author already mentioned some geophysical peculiarities of the mid-1908. But there are also some signs that they began earlier. The spring of 1908 was rather unusual. There were very strong floods on many Russian rivers. For example, Moskva-river (which had a record flood for the whole previous 100 years period), Oka-river, Volga-river. Large areas were flooded.
It is interesting to recall the work [60], where it was discovered that a high Mississippi river level suppresses local earthquakes 3 months after and induces 9 months after, but the number of reports on unusual luminous phenomena is increased a few months after, i.e. when earthquakes are suppressed. On the other hand, in [60] there is an example of the "airship" event during which odd, nocturnal luminosities were seen over more than a dozen central and southern USA states from January through April, 1897. At the time one of the greatest floods to have ever affected the midwestern USA, was occurring. One month later, on 31 May, the intense Giles Country, Virginia earthquake struck "and the airships were seen no more". In some way, it resembles the 1908 events, as some authors state that during the 1908 spring there were the numerous reports about unusual luminosities, and the places of their appearance were drifting from the European part of Russia to Siberia, and that after the Tunguska the luminosities disappeared. But, of course, the definite conclusion can't be done now.
Let's continue with the geophysical peculiarities of the first half of 1908. On May 23/24 it strong snowed in Switzerland. On June 5 and 6 it snowed in S-Petersburg and Petrozavodsk, Russia. Many unusual atmospheric phenomena were seen; a great number halos, strange rainbow etc. But, of course, the most remarkable were phenomena seen on the night (evening) sky. In the evening, March 27 an unusual sky illumination was seen in the north-eastern parts of USA and a thousand km from the shore [61]. It was described as never seen before and in many aspects resembled the sky glow of late June-early July 1908. The author also should mention that similar phenomenon was seen on the evening March 26 and the following several nights in the town of Yur'yev, Russia (now Tartu, Estonia). On this days a geomagnetic activity was enhanced, but as, already mentioned, the glows didn't look like usual aurora. On May 27 the first time since 1906 the "sky-colored clouds" were seen in UK [62]. The next days the sky was too cloudy.
Here we come up to the atmospheric abnormalities of late June-early July 1908. In [46] they are explained as, i) the explosive development of noctilucent clouds; ii) the increased luminosity of the night sky glow. Let's think about their possible origins. Now it is usually thought that for development of noctilucent clouds 3 main conditions must exist: a low temperature at about 80-90 km height, a presence a sufficient quantity of water vapor and small nucleus of water vapor condensation. What could be the cause of the upsurge in any of them?
At first, let us remark, that the late June-early July is the season maximum of a noctilucent clouds appearance. Moreover, as we already saw, this time was the time of the large-scale weather break, roughly speaking, from drought to thunderstorms. In other words, in the atmosphere the quantity of water vapor was significantly increased.
The following factors could also "help" the noctilucent clouds formation. The first one is the increase of the solar activity in the late June. It is known that the increase of the solar activity leads to some decrease of the atmospheric transparency, probably due to build up of microparticles, i.e. condensation nucleus. And also solar flares, and especially solar proton events could lead to the cooling of the middle atmosphere [63]. The author also proposed that the increased tectonic activity could produce an upsurge in the Earth degassing and some of the gases through various chemical reactions could lead to elevated quantity of water vapor in the atmosphere. Anyway, the majority of the noctilucent clouds registrations from the "Salyut" spacestation was over the regions with high volcanic and seismic activity [64]. And finally, the Tunguska explosion itself could lead to a cooling of the upper atmosphere and an upsurge of the noctilucent clouds formation due to a generation of acoustical-gravity and other atmospheric waves [65].
The sky glow of the late June-early July produced no appreciable absorption of a light: "though thin, they were strongly illuminative, and stars shone through them with surprising distinctness" [50]. The daily atmospheric absorption measurements in Paris [46] also revealed no extraordinary absorption on the days of the sky glow, but, as usually on the eve of a weather change, a polarization have changed [46], revealing the appearance of small nucleus in the atmosphere. The author discovered monthly averaged data on absorption in Irkutsk, and they also revealed no anomalies [66]. The detailed analysis of the Smithsonian Astrophysical Observatory data on absorption in USA [12] also revealed that no increase of dust in the atmosphere is associated with the Tunguska, just increased water vapor quantity.
So, despite we don't understand the physics of the processes well, the unusually large appearance of noctilucent clouds conforms with the geophysical situation of that period and the air-waves from the Tunguska explosion probably also made a contribution.
Now let's consider the increased luminosity of the night sky glow. At first, the author would like to mention that the sky glow phenomenon occurred in connection with earthquakes (see also section 3.1). Here are just 2 examples. The earthquake happened September 12, 1841 near Russian town of Nizshnii Tagil. At 2. a.m. a thunder-like rumble was heard and the ground trembled. At 4 a.m. the sky was flooded with the pink light, which at 5 a.m. transformed to the yellow one. The whole day the sky was yellowish, and filled with a smoke. At the place located 40 km to the south-west from Nizshnii Tagil at first a fiery cloud appeared at 5 a.m. on the north-west and for a few hours spread all over the sky. No wind. The second example is the ill-fated Rumanian earthquake of March 4, 1977. From the western part of USSR the permanent pink sky glow was seen with flashes imposed on it. In Rumania the sky glow was in western direction from the earthquake epicenter [55].
Another intriguing luminous phenomenon is probably related with submarine volcanoes activity 1000-2000 km away from it [67]. On 9 April 1984, crews of three separate commercial airlines observed a gigantic mushroom-like weakly luminous cloud. It reached an altitude of about 18 km and a diameter of 320 km for about 2 minutes. No other abnormalities were observed. After the detail research, the connection was proposed with the upsurge of the submarine volcanoes activity about 1000-2000 km from the cloud, but the physical mechanism is still a mystery.
So the first cause for the large-scale sky glow could be the large-scale activation of tectonic processes. Of course, with the present day knowledge we can just propose it and can't prove. But the most important is that similar sky glows happen many times without any giant meteorite or comet. We begin with cases of just luminous spots in the night sky. When this phenomenon looks like bands on the sky, it is sometimes called "non-polar aurora". Some displays seem related to auroras, while others not. German researcher Hoffmeister C. studied this phenomenon for many years. He got their altitudes 90-180 km, with distinct maximum at 120-130 km. According to Hoffmeister's opinion, their spectrum is the enhanced usual night glow one, and they are closely related with noctilucent clouds. He discovered their correlation with disturbances of radiowaves ( wave lengths 350-530 m) propagation. He also conducted statistical analysis and revealed 12 yearly (i.e. 'inside' year) maximums, with one of them on June 18-30. Below are several examples of luminous spots taken from [55].
Returning to the Tunguska, we see again the probable role of the acoustic gravity waves, excited by the Tunguska explosion, as well as lunar-solar tide (the angle between the Moon and the Sun was rather small on the Tunguska days).
Now let's examine the cases of the whole sky glows, which often called "glowing night skies" [55].
So, these luminous phenomena are rare, but not unique events. The physical mechanism is not known, but the author probably can say, why we could expect their appearance at the late June-early July 1908.
The first and probably the most important argument is so called "weather lights" [55]. Usually they are luminous whitish or reddish patches on the horizon, often mobile, and located at any azimuth. Their appearance followed by a sharp weather change, generally a storm [55]. As we are aware, the early July there was a large scale weather break to thunderstorms (also favorable for NNE). A good example of a similar glow on mini-scale is the sky glow on December 23, 1916 (see above).
It is interesting, that "earthquake lights" tend to occur during a passage of cold weather front!
Another argument is the upsurge of the atmosphere glow sometimes seen by cosmonauts from spacestation by naked eyes [64]. The phenomenon consists of several parts. i) The appearance of the second luminous layer of the atmosphere at 250-350 km heights. ii) The increase of the luminosity of the well-known first luminous layer at about 90 km height. iii) The complete glow of the whole atmosphere. It is interesting that the areas with the second luminous layer coincide with the areas of increased proton and electron radiation intensity and increased ionospheric turbulence. Usually these phenomena tend to occur during geomagnetically calm period between geomagnetic disturbances and during solar flares (see also above on the glow of November 30, 1959). As we know, the late June-early July 1908 was a period of increased solar activity.
Sometimes glow was seen even above the spacestation, and one time the visible reddening of bright stars was registered! Indeed, our planet still has a lot of puzzles!
And finally the last, but very important factor.So, the author think that the 1908 Tunguska event and the sky glow of late June-early July 1908 are just different manifestations of the same 'interesting' geophysical situation of that time.
As we saw, there are a lot of examples of small-scale Tunguska. But do besides Tunguska powerful events occur? In the author opinion the answer is positive. Let's look through the known history. Even some events described by ancient authors hint on their possible NNE origin. Of course, we can understand ancient writers descriptions very badly, so the author could talk just about "suspected" events. Here are just everal examples.
The circumstances of the event hint on NNE. It is supported by that the prominent Suphan Dagi volcano is sleeping on Lake Van shore, and this area is the area of increased tectonic activity (earthquakes occurred rather often),
In [70] it was proposed, that it was caused by a large extraterrestrial projectile. According to geological research, this crater is a geological formation [70]. In the author opinion, existing data favour for endogenic origin (NNE), this area is the area of increased tectonic activity (earthquakes happen from time-to-time).
This was the time of "light nights"[71].
In Naples, Italy, in the evening, when the sun was 25 degrees below the horizon, a light was observed in the north, as if the air was on fire, and flashing. At 3 a.m. it was much brighter and spread much westward. Its greatest height was about 65 degrees. The light boundaries were jagged, and scattered, and follow the course of the westerly wind. Stars of 3-th and 4-th magnitude could be easily seen through it. About 4 a.m. a very regular arch was seen to rise gently. About the 6 a.m. the intenseness of the color disappeared, and it vanished at 7.30 a.m.
In [71] there is a reference on the preceding eruption of the Vesuvius volcano, but the closest preceding eruption the author is aware was just in May, 1737.
In Padua, Italy, after sunset on the preceding days, as well as Dec. 16, there appeared in the west a remarkable redness. The same glow happened and on the following evening. On the evening Dec. 16 the air was calm and the barometer was remarkably high. At 5.15 p.m. there appeared near the horizon a blackish zone. Above this zone was another very luminous, resembling the dawn pretty advanced. The highest zone was of a red fiery color. Eastward they extended to the 55 degrees on the horizon, and westward to the 70 degrees. Near zenith there appeared some thin lucid clouds. A little after 6 p.m. the upper part began to emit streamings, or rays, in plenty. Its color was red mixed with whitish and darkish. In a few seconds after, there issued out from the very equinoctial west, a red and very bright column, and a little later, it became curved in the shape of the rainbow. At 8.30 a.m., almost in an instant the bright zone, from the 8 degrees west to the 50 degrees east, became more vivid, and rose higher; and above this appeared a new large one, of a red fiery color, with several successive streaming tending upward, and passing 60 degrees of altitude; the western part had assumed the form of a thin cloud. At 12 p.m. the light was nearly extinct. Twenty minutes after, there appeared a white brightish beam, at 30 degrees west and 60 degrees high, but it soon became invisible. In half an hour later, a very weak light remained in the west, near the horizon.
In Bolonia the glow was so very remarkable that no one remembers to have ever seen the like, it was possible to distinguish houses at a great distance. At 8 p.m. the glow formed itself into a concave arch towards the horizon. The polar star was near the top of its convexity, and some stars shone bright in the midst of the light. At 8.34 p.m. the red light continued spreading. At the upper part, a considerable part of heavens was enlightened with a very vivid red light, which was interrupted by several vertical streaks or columns of a bright yellowish light. At 9.04 p.m., there remained but a little reddish light at the north pole, all the rest was collected near the zenith. In the south, where the sky was clear, there were seen some of those meteors, called falling stars. Several persons reported that in the evening Dec. 16 they perceived a certain stench in the air. There was a very thin fog in the air not only on Dec. 16 but also on the preceding and following days. The mornings of Dec. 17, 18, before and a little after sunrise, the air appeared of an uncommon fiery color. The evening of Dec.17 the crepusculum was of an extraordinary height. Between the north and west, there was seen a very thin fiery red "vapour", which lasted almost till night.
At Edinburgh, England, at 6 p.m. on looking out at windows, the sky was in flame. There was an arch of this red light reached from the west, over zenith, to the east. The northern border of this light was tinged with somewhat of a blue color. This glow did not look like common aurora. It gradually and gently stole along the face of the sky, till it had covered the whole hemisphere. A great circle of the glow came from the west to the zenith.
At Sussex, England. It was a strong and very steady red light. It did not seem to dart or flash at all, but continued going on in a steady course against the wind, which blew fresh from the south-west. It began about north-north-west, in form of a pillar of light at about 6.15 p.m. In about 10 minutes, a 4-th part of it divided from the rest, and never joined again. In 10 minutes more it described an arch, but didn't join the top. Exactly at 7 p.m. it formed a bow, and soon after quite disappeared. It was all the while lightest and reddest at the horizon. At 8 p.m. it began again exactly north. In half an hour it made an arch from east to west, and went quite away to the south, when it ended much with the same appearance as it began in the north, but not quite so red.
At Sheffield, England, at 5 o'clock, afternoon, and all the evening appeared a remarkable brightness in the sky, of a blood-red color, very bright [72].
At Philadelphia on Dec. 16 nothing unusual was seen, but on Dec. 18 an earthquake struck. And "the second evening after, and for several evenings in that month, a red vapour appeared to the south and south-west, like the aurora borealis" [73]. On November 28, about sunset, many people in this town saw a fiery "meteor" in the air, large and bright, it seemed in the zenith, and so it seemed to others some miles from the town.
At Solikamsk, Russia (59.6 N, 56.8 E) on Dec. 17 night as a red light was everywhere above. In the morning it was hazy and stuffy. On Dec. 24 and 25 the phenomenon repeated in smaller degree.
In Chiloe Island, Chile, on Dec. 30 the fiery cloud from the north traversed the archipelago [55].
But probably the most remarkable event occurred at Kilkenny in Ireland on Dec. 16. A great ball of fire appeared, which burst with an explosion that shook great part of the island, and set the whole hemisphere on fire, which "burned most furiously, till all the sulphureous matter was spent." [72]. In [55], cited another source, it was written that on Dec. 26 (probably misprint), much of the Southern Europe was covered by a reddish, luminous haze. At Kilkenny it appeared like a ball of fire in the air, which lasted about an hour and then burst into pieces.
There is a tectonic fault near Kilkenny, and weak small focal depth earthquakes happen in there from time-to-time.
Why not the Ireland Tunguska of 1737!
The author inclines to think that extremely powerful NNEs played some role in astrobleme's formation millions years ago [3].
The author thinks that the present material clearly points out to the endogenic origin of the 1908 Tunguska event, or, at least, the endogenic interpretation conforms with the facts much better then the meteoritic one.
Anyway, there are a lot of things to investigate about our miraculous planet, which, no doubt, will present us a much more puzzles!
My experience in contacts with scientists and general public reveals some typical questions, which are asked about the tectonic Tunguska. Below I summarize them.
What do other scientists say about your idea?
In 1990, when I sent my article on the tectonic Tunguska to the PHYSICS
OF THE EARTH journal, they were surprised with it, but were to recognize
that there were no mistakes in it. So they have accepted and have printed
it. Since that time the tectonic Tunguska got many supporters (you can
understand it, if look at the abstracts of the
Tunguska 98 conference, for example). But of
course, if you wrote many articles, for example, on the asteroid/cometary Tunguska,
you will not be glad with the popularity of the tectonic one. Just read a citation below
from http://www.spaceref.com/news/viewpr.rss.html?pid=25819
Why do you think that your explanation is better than
a cometary one?
Because if you peruse arguments for the "cometary Tunguska", you will
see that there is no solid argument in its favour! Moreover, there are
a lot of arguments (many of them are very reliable and solid) against
cometary Tunguska. By the way, many scientists prefer to talk about a
stony asteroid fall in Tunguska, just because the extremely large
problems with the cometary Tunguska.
Remarkably, that the cometary Tunguska itself has appeared just because
there were very large problems with the "stony asteroid Tunguska"!...
In my opinion the "tectonic Tunguska" nowadays is the best in explaining
the Tunguska event.
Interestingly, that when I sent my article on the tectonic interpretation
of the Tunguska event to PHYSICS OF THE EARTH journal in 1990, I knew not
much on Tunguska. Since that time more and more new facts in favour of
the tectonic intepretation appear.
And the tectonic interpretation was the only theory, which was able
to predict new results in Tunguska - related meteorological
peculiarities (see pos. 3.4)
Do you think that Tunguska was an earthquake?
No, if you ask: "was it just an earthquake?". According to modern
encyclopedias, an earthquake is trembling of a ground produced by earth's
rupture. But, for example, earthquakes lights are out of this definition.
And indeed, some of them appear hours, days, and even weeks before an
earthquake. So it would be strange to say that a burnt (by an earthquake
light ) roof in a house a couple weeks before the August 16, 1976
earthquake in China was caused by that earthquake!
So the phenomena are another way of manifestations of tectonic processes,
besides rupture of the ground (i.e. earthquake itself). And observational
data point that atmospheric conditions play a large role in the
manifestations too. It seems that it is a way of coupling of the
subterranean and atmospheric processes, possibly involving some
electromagnetic mechanisms, but we still poorly understand it.
You can read more in my
geophysical meteors www-article.
In typical cases the phenomena are not very energetic, but in Tunguska
there was a very rare combination of supportive/intensifying factors (see
above), which apparently made them so energetic.
Do you know other geophysical events, similar
to Tunguska?
There are several events, which in my opinion were probably "other
Tunguskas" (see pos. 3.13).
On mini and micro-scales similar events occur rather often (see pos.
3.3), and
geophysical meteors www-article).
What is the difference between NNE and a geometeor?
NNE seems to be a little bit more general term. But NNE is often precede
by a geometeor, and when a geometeor explodes - it is a NNE. So in many
cases they are closely related. NNE is a temporarily term, proposed to use
just untill we better understand physics of the explosive phenomenon.
1. Ol'khovatov, A.Yu., O veroyatnoi roli seismotectonicheskikh protsessov v Tungusskom fenomene 1908 g. // Izvestiya AN SSSR, Fizika Zemli, N 7, p.105 (1991) (in Russ.).
2. Ol'khovatov, A.Yu., The meteorite that never was. // Science in Russia, N 2, p.19. (1996) (unfortunately due to translation there are some inaccuraties).
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Go to the A. Ol'khovatov Web-site directory in English: http://olkhov.narod.ru/tunguska/index.html
