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United States · Shield volcano

Mount Okmok

Okmok

Type
Shield volcano
Elevation
1073m
Last eruption
2008
Mount Okmok
Photo: J. Reeder. Alaska Division of Geological and Geophysical Surveys · Public domain · Wikimedia Commons
Type
Shield volcano
Country
United States
Region
North America / Aleutian Ridge Volcanic Arc
Elevation
1073m
Coordinates
53.430, -168.130
Last eruption
2008
Tectonic setting
Subduction zone / Intermediate crust (15-25 km)
Landform
Shield
Major rock type
Basalt / Picro-basalt

Geological summary

The basaltic Okmok shield volcano forms the NE end of Umnak Island in the Aleutian Islands. The summit of the low, 35-km-wide volcano is cut by two overlapping 10-km-wide calderas formed during eruptions about 12,000 and 2,050 years ago when dacitic pyroclastic flows reached the coast.

Excerpt from the Global Volcanism Program, Smithsonian Institution · Read the full summary on GVP →

From Wikipedia

Mount Okmok is a volcano on eastern Umnak Island, in the central-eastern Aleutian Islands of Alaska. Part of the Aleutian Volcanic Arc, it was formed by the subduction of the oceanic Pacific Plate under the North American Plate. Okmok is a large shield volcano capped by a 10-kilometer (6.2 mi) wide caldera. The caldera contains numerous cinder cones, their lava flows, and a few lakes. Okmok erupts mainly basaltic lava, mostly from the cones within the caldera.

Wikipedia · CC BY-SA · Read full article →

Eruption history

19 recordedGlossary

Record summary

Confirmed eruptions
18
Uncertain eruptions
1
Span of confirmed record
6310 BCE (±500 yrs) – 2008
Largest confirmed eruption
VEI 6 (100 BCE)
Confirmed eruptions since 1900
11
Summary (VEI over time)
Click a bar to see individual eruptions · Use arrow keys to move between bars, Enter to open
6310 BCE~6033 BCE · 1 eruptions · max VEI 4210 BCE~67 · 1 eruptions · max VEI 61731~2008 · 17 eruptions · max VEI 46310 BCE4369 BCE2151 BCE210 BCE1731

Detailed timeline

  1. 2008VEI 4Observed
    2008-07-12 – 2008-08-19
    NE caldera floor
  2. 1997VEI 3Observed
    1997-02-11 – 1997-05-19
    SW part of caldera (Cone A)
  3. 1986VEI 2Observed
    1986-11-18 – 1988-02-26
    SW part of caldera (Cone A)
  4. 1983VEI 2Observed
    1983-07-08 – 1983-07-08
    SW part of caldera (Cone A)
  5. 1981VEI 3Observed
    1981-03-24 – 1981-03-24
    SW part of caldera (Cone A)
  6. 1960VEI 3Observed
    1960-10-15 – 1961-04-15
    SW part of caldera (Cone A)
  7. 1958VEI 3Observed
    1958-08-14 – 1958-08-25
    SW part of caldera (Cone A)
  8. 1945VEI 2Observed
    1945-06-04 – 1945-12-16
    SW part of caldera (Cone A)
  9. 1943VEI 1Observed
    1943-06-16 – end unknown
    SW part of caldera (Cone A)
  10. 1938VEI ?Observed
    1938-07-02 – end unknown
    SW part of caldera (Cone A)
  11. 1936VEI ?Method not stated
    1936-07-02 – end unknown
    SW part of caldera (Cone A)
  12. 1931VEI 2Observed
    1931-03-21 – 1931-05-13
    Cone A?
  13. 1899VEI 3Observed
    1899-07-02 – end unknown
    SW part of caldera (Cone A)
  14. 1878VEI 2Observed
    1878-07-02 – end unknown
    Cone A?
  15. 1824VEI ?Observed
    1824-07-02 – 1830-07-02
    Cone B?
  16. 1817VEI 3Observed
    1817-03-01 – 1820-07-02
    Cone E? or B?
  17. 1805VEI ?Observed
    1805-07-02 – end unknown
  18. 100 BCE (±50 yrs)VEI 6Geological estimate
    100 BCE – end unknown
    Okmok II caldera
  19. 6310 BCE (±500 yrs)VEI 4Geological estimate
    6310 BCE – end unknown

Nearby volcanoes

External links

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