|Catalogue of Canadian volcanoes|
Catalogue of Canadian volcanoes
Garibaldi volcanic belt: Garibaldi Lake volcanic field
Figure A3. Landsat image
This Landsat image of the area surrounding Garibaldi volcano shows several different volcanic features including lava flows (Ring Creek, Rubble Creek, Clinker Ridge), a volcanic neck (The Black Tusk), and a partly eroded stratovolcano (Mount Garibaldi, Atwell Peak, Dalton Dome). Also visible is The Barrier, which has been the source of several catastrophic rock avalanches. The approximate outline of the Squamish District Municipality is also shown for reference.
Garibaldi volcano is an eroded, dacitic stratovolcano in southwestern
British Columbia; like Mount Baker to the south, it is part
of the Cascade volcanic arc. Garibaldi volcano, 80 km due north
of Vancouver, is made up of Mount Garibaldi, Atwell Peak, and
Dalton Dome (Figure A3, Figure A4).
This Pleistocene volcanic centre is a part of a volcanic field
that contains some 13 vents in an area 30 km long by 15 km wide,
much of which is in Garibaldi Provincial Park.
The eruptive history of Garibaldi volcano involves an initial period of volcanism
(200,000-300,000 years ago) followed by a period of quiescence.
Renewed activity in the last 50,000 years has rebuilt the edifice
in a series of violent eruptions, similar in character to those
that issued from Mount Pelée in 1902 and destroyed the
town of St. Pierre on the island of Martinique. As successive
pyroclastic flows travelled down the mountain's gentle slopes
and were deposited, the volcano took on a broad, conical form.
Part of the volcano's southwest flank built out onto thick glacial
ice filling the Squamish River valley (Figure A3).
Subsequent rapid melting of the ice at the close of the last
ice age removed support from the western part of the cone. The
volcano collapsed, producing much of the existing rugged topography
of Mount Garibaldi and Atwell Peak. This catastrophic failure
left a scarp on which is exposed the internal structure of the
volcano and a debris fan with an estimated volume of 150,000,000
m³ at the foot of the mountain north of the town of Squamish.
As valley glaciers retreated, two lava flows erupted from Clinker
Peak, immediately north of Garibaldi volcano (Figure A3).
The northernmost Rubble Creek flow was partly confined by
a wall of ice, resulting in a lava flow over 244 m (800
ft.) thick. The steep, northern edge of the Rubble Creek
flow partly collapsed several times, most recently in
1855-1856 (Figure A5).
The village of Garibaldi was abandoned because of the
danger of future collapses. The most recent period of
activity occurred shortly after the disappearance of
the glacial ice filling the valley, 10,700 to 9300 radiocarbon
years ago, and ended with the eruption the Ring Creek
lava flow from Opal cone, on Garibaldi's southeastern
flank (Figure A3). The Ring Creek flow is very unusual.
It is 15 km long - a length usually only attained by fluid basalt flows,
except that the Ring Creek flow is dacite.
Figure A4. Four volcanoes of Garibaldi Volcano
View looking south of four volcanoes with different morphologies. Garibaldi volcano, which encompasses three different mountain peaks (Mount Garibaldi, Atwell Peak, and Dalton Dome), is the large stratovolcano in the background. Table Mountain is a flat-topped, steep-sided volcano that erupted under glacial ice. Clinker Peak and Mount Price are the volcanoes in the foreground. Prominent levees are visible emanating from Mount Price. These levees demarcate the edges of a lava flow that erupted about 10,000 years ago.
(Photograph by C.J. Hickson (Geological Survey of Canada))
Figure A5. Mount Price
Lava flows emanating from Mount Price flowed towards the Cheakamus River valley (foreground). At the time of eruption, the valley was filled by glacial ice. The lava flow was stopped by the ice and ponded, eventually cooling. When the ice melted away, the ice-cooled lava-flow front formed a precipitous cliff; water ponded behind the lava dam, forming Garibaldi Lake (ice-covered lake to the left). The steep cliff failed in a series of landslides, the most recent of which occurred in 1855-1856. The location is referred to as 'The Barrier'. View to the east-southeast.
(Photograph by C.J. Hickson (Geological Survey of Canada))
Renewed volcanism in the Garibaldi area would pose a serious threat
to the local communities of Whistler and Squamish. Altthough
no Plinian-style eruptions are known, even Pelean-type eruptions
could produce large quantities of ash that could significantly
affect these nearby communities. Ash columns could rise to several
hundred metres above the volcano whose close proximity to Vancouver
would make this a hazard for air traffic. The danger from lava
flows would be low to moderate because the nature of the lavas
would prevent them from travelling far from their source, even
though the Ring Creek lava flow ends only 6 km from Squamish.
Melting of remnant glacial ice capping the Mount Garibaldi area
could produce floods, lahars, or debris flows that might endanger
small communities including Brackendale. Highway 99, which links
Whistler and Squamish with Vancouver, is already plagued by
landslides and debris flows from the precipitous Coast Mountains.
An eruption producing floods could destroy segments of the highway.
Flooding and debris flows could also have serious consequences
for the salmon fishery on the Squamish, Cheakamus, and Mamquam
rivers. In addition, explosive eruptions and the accompanying
ash could cause short- and long-term water-supply problems for
Vancouver and much of the lower mainland. The catchment area
for the Greater Vancouver watershed is downwind from the Garibaldi
area. Air-fall material could also have a deleterious effect
on the ice fields to the east of Garibaldi volcano, causing
increased melting and spring flooding. This in turn could threaten
water supplies from Pitt Lake as well as fisheries on the Pitt River.