Deschutes & Ochoco National Forests
Crooked River National Grassland

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Deschutes National Forest
1001 SW Emkay Drive
Bend, OR 97702

(541) 383-5300

Ochoco National Forest
3160 N.E. 3rd Street
Prineville, OR 97754

(541) 416-6500

Crooked River National Grassland
813 S.W. Hwy. 97
Madras, OR 97741

(541) 475-9272

Geology

Holocene Eruptions

During the last 10,000 years (Holocene) there have been numerous periods of eruptive activity involving eruptions from over 75 different eruptive vents.

	Geologic Summary
	Geomorphic Provinces
	Geothermal Energy
	Holocene Eruptions
	Local Earthquakes
	Oregon Volcanoes
	Soils

ERUPTION	LOCATION	AGE	TYPE	FEATURES
South Cinder Peak	South of Mt. Jefferson	about 1000 A.D. age based on stratigraphic estimate	Basaltic	Cinder cone Lava flows
Big Obsidian Eruptive Episode	Newberry Caldera	about 700 A.D. age based on C14 date of 1310 yrs BP (1260 calendar yrs BP)	Rhyolitic	Newberry Pumice (airfall deposit) Paulina Lake Ashflow Big Obsidian Flow
Blue Lake Eruption	Belknap Volcanic Field	about 675 A.D. age based on C14 date of 1330 yrs BP (1275 calendar yrs BP)	Basaltic	Explosion crater Spatter cone chain Tephra deposit
Belknap Crater	Belknap Volcanic Field	about 650 A.D. age based on C14 date of 1400 yrs BP (1300 calendar yrs BP)	Basaltic	Shield Cinder cone Lava flows Secondary shield and lava flows (Little Belknap)
Collier Cone Eruption	Belknap Volcanic Field	about 440 A.D. age based on C14 date of 1600 yrs BP (1510 calendar yrs BP)	Basaltic	Cinder cone Lava flows
Lost Lake Cones Eruption	Sand Mountain Volcanic Field	about 70 A.D. age based on C14 date of 1950 yrs BP (1880 calendar yrs BP)	Basaltic	Cinder cones
Devils Hill Eruptive Episode	South Sister	about 60 A.D. age based on C14 date of 1970 yrs BP (1890 calendar yrs BP)	Dacitic	Devils Hill chain of vents - 15 domes Newberry Flow - dome and large flow Carver Lake vents - 4 domes Devils Hill Tephra - airfall pumice
Four-in-One Cone Eruption	Belknap Volcanic Field	about 40 A.D. age based on C14 date of 1980 yrs BP (1910 calendar yrs BP)	Basaltic	Cinder cone Lava flows
Rock Mesa Eruptive Episode	South Sister	about 180 B.C. age based on C14 date of 2150 yrs BP (2130 calendar yrs BP)	Dacitic	Rock Mesa - dome and large flow Rock Mesa ENE - small dome Rock Mesa Tephra - airfall pumice
Sand Mountain Eruptions	Sand Mountain Volcanic Field	about 850 B.C. age based on many C14 dates ranging from 2590 yrs BP (2740 calendar yrs BP) to 2990 yrs BP (3190 calendar yrs BP)	Basaltic	Cinder cones Lava flows
East Lake Eruptive Episode	Newberry Caldera	about 1550 B.C. age based on hydration date	Rhyolitic	East Lake Obsidian Flows
Black Rock Eruptive Episode	Davis Lake area	about 3540 B.C. age based on C14 date of 4740 yrs BP (5490 calendar yrs BP)	Basaltic	Davis Lake Flow and cinder cones North Black Rock Flow and cinder cone South Black Rock Flow and cinder cone
Northwest Rift Eruptive Episode	Newberry Volcano	about 5050 B.C. age based on many C14 dates ranging from 5800 yrs BP (6640 calendar yrs BP) to 6380 yrs BP (7240 calendar yrs BP)	Basaltic	Lava Butte/Gas-Line Segment Lava Butte - large cinder cone Lava Butte Flows Gas-Line Flows Spatter ramparts Mokst Butte Segment Mokst Butte - large cinder cone Mokst Butte Flows Spatter cones South Kelsey Segment Small cinder cone Spatter cones South Kelsey Flows Sugarpine Segment Large cinder cone Spatter cones and ramparts North Sugarpine Flows South Sugarpine Flows Lava Cast Forest Segment Spatter cones and ramparts Forest Road Flows Lava Cast Forest Flows Lava Cascade Flows Hidden Flows North Summit Segment Spatter cones and ramparts Unnamed flow North Summit Flows East Lake Fissure Surveyor Segment Small cinder cone Spatter ramparts Surveyor Flows
Interlake Eruptive Episode	Newberry Caldera	about 5100 to 5320 B.C. ages based on stratigraphy and C14 date of 6400 yrs BP (7270 calendar yrs BP)	Rhyolitic	Interlake Obsidian Flow and related pumice deposits (5100 B.C.) Central Pumice Cone and related flows (5200 B.C.) East Lake Tephra (5320 B.C.)
Forked Butte Eruptions	South of Mt. Jefferson	about 5400 B.C. age based on stratigraphic estimate	Basaltic	Forked Butte and another cinder cone Lava flows
Climactic Eruption of Mt. Mazama	Crater Lake	about 5680 B.C. age based on C14 date of 6845 yrs BP (7630 calendar yrs BP)	Rhyolitic	Caldera Mazama Tephra
Llao Rock Eruption at Mt. Mazama	Crater Lake	about 5850 B.C. age based on C14 date of 7015 yrs BP (7800 calendar yrs BP)	Rhyolitic	Dome and flow Tephra
East Rim Eruptive Episode	Newberry Caldera	about 9210 B.C. age based on C14 date of 10000 yrs BP (11160 calendar yrs BP)	Basaltic	Cinder cones and spatter ramparts Lava flows

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USDA Forest Service - Deschutes & Ochoco National Forests
Last Modified: Wednesday, 26 November 2003 at 12:01:59 EST