Newberry National Volcanic Monument
Deschutes National Forest

Newberry Volcano

Type: shield-shaped volcano with caldera
Activity: dormant
Last Eruption: 1300 yrs ago
Rock Type: basalt to rhyolite
Eruptive Volume: 450 cu km
Latitude: 43.69 N
Longitude: 121.25 W
Location Map
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Newberry Photo Menu

GEOLOGIC BACKGROUND:

Newberry Volcano is a shield shaped composite volcano, about 40 miles north-south and 25 miles east-west. During its more than half million year history of activity, including caldera collapse and subsequent caldera-filling volcanism, Newberry has erupted often, including several times in the Holocene. The volcano rises about 3,600 feet above the surrounding area but covers an area of in excess of 500 square miles and has a volume of over 110 cubic miles. The erupted volume is probably substantially greater than this, because lava flows and alluvium from Newberry extend more than 40 miles beyond the base of the volcano.

The east and west flanks of the volcano consist almost entirely of ash-flow and air-fall tuffs, alluvial deposits, and a few basaltic flows. The north and south flanks, on the other hand, cover mainly by basaltic andesite cinder cones and lava flows.

There are approximately 400 basaltic cinder cones and fissure vents on the flanks of Newberry (majority are on the north and south flanks). These vents are the source of the many flows that cover much of the surface of the volcano. Dacite, rhyodacite, and rhyolite domes and flows also occur at many localities on the middle and upper flanks of the volcano.

The summit caldera of Newberry is approximately 5 miles east-west and 4 miles north-south. The west wall of the caldera is only a few tens of feet high where Paulina Creek has cut a channel to drain Paulina Lake. In other areas of the caldera the walls are 500 to 1600 feet high. The caldera was initially deeper by at least 1600 feet but has been filled during late Pleistocene and Holocene time by pyroclastic rocks, flows, domes and sedimentary rocks.

During the late Pleistocene and Holocene there have been six eruptive episodes; four rhyolitic (east half of the caldera) and two basaltic (on the flanks).

• South Obsidian Eruptive Episode: An estimated 12,000 calendar yrs ago, an obsidian dome and related obsidian flow erupted in the southeast part of the caldera.
• East Rim Eruptive Episode: About 11,200 calendar yrs ago (10,000 C14 yrs B.P.), mafic cinders, scoria, spatter, and lava flows erupted from a fissure on the east rim of the caldera.
• Interlake Eruptive Episode: A series of rhyolitic eruptions began in the caldera approximately 7,300 calendar yrs ago (6,200 C14 yrs B.P.). They produced a widespread phreatomagmatic pumiceous tephra deposit, obsidian flows, large and small pumice cones, and a pumice ring. This eruptive episode probably lasted for about 200 years.
• Northwest Rift Eruptive Episode: About 7,000 calendar yrs ago (6,100 C14 yrs B.P.), basaltic andesite lava and cinder cones erupted from extensive fissure vents on the northwest and south flanks of Newberry. Spatter and cinders also erupted from a fissure on the north caldera wall. The lava flows range up to 9 km long and are more voluminous at lower elevations. This eruptive episode probably lasted for less than 50 years.
• East Lake Eruptive Episode: About 3,500 yrs ago, obsidian flows and associated pumice deposits in the caldera erupted from caldera ring fractures.
• Big Obsidian Eruptive Episode: About 480 A.D. (1,470 calendar years B.P.), a 3-part sequence of rhyolitic eruptions began, which included an air-fall tephra, ash-flow tephra, and an obsidian flow, from a common vent at the base of the south caldera wall. The initial Plinian eruption 480 A.D. (1,580 C14 yrs B.P.) produced the Newberry pumice fall deposit which blanketed the east flank of the volcano and areas to the east. About 210 yrs later the Paulina Lake ash flow (1,310 C14 yrs B.P.) spread from near the south caldera wall to Paulina Lake. The final phase of the eruption produced the Big Obsidian Flow which covers 2.8 sq km.

Map of Newberry Caldera (22k gif)
Map of NW Rift Zone (17k gif)
Map of Lava Butte Flow (52k jpg)

HISTORIC ACTIVITY:

Hot springs occur in East and Paulina Lakes.

RECENT STUDIES:

• Julie Donnelly-Nolan of the U.S. Geological Survey is studing of the volcanic hazards of Newberry Volcano.
• Bob Reynolds of Central Oregon Community College is looking at the underwater geology of Paulina and East Lake.
• Bob Jensen and Larry Chitwood from the Deschutes National Forest found evidence for a large prehistoric flood along Paulina Creek and for uplift of the caldera floor.
• Steve Kuehn from Washington State University has looked at the Holocene and latest Pleistocene tephras of Newberry Volcano.
• Bob Jensen studied the explosion craters on the surface of the Big Obsidian Flow.

ADDITIONAL INFORMATION: (these links all open in a pop up window)

• Link to U.S.G.S. - CVO's Newberry Volcano Info
• Link to U.S.G.S. Visit a Volcano Info for Newberry Caldera
• Link to U.S.G.S. Visit a Volcano Info for Lava Butte
• Link to Volcano World's Newberry Volcano Info