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Mount Okmok

Okmok

Gunung api perisai · United States · 1073 m

The summit of 35-km-wide Okmok has two largely overlapping 10-km-wide calderas. Both calderas formed by voluminous eruptions of tephra and pyroclastic flows during the Holocene, one about 8,250 years ago and the other about 2,400 years ago. Numerous cones and lava domes formed on the caldera floor and flanks. Historical explosive eruptions and lava flows have originated from cones within the caldera.
The summit of 35-km-wide Okmok has two largely overlapping 10-km-wide calderas. Both calderas formed by voluminous eruptions of tephra and pyroclastic flows during the Holocene, one about 8,250 years ago and the other about 2,400 years ago. Numerous cones and lava domes formed on the caldera floor and flanks. Historical explosive eruptions and lava flows have originated from cones within the caldera. · Foto: Photo by John Reeder (Alaska Division of Geological & Geophysical Surveys). · Wikimedia Commons
Tipe
Gunung api perisai
Negara
United States
Wilayah
North America Volcanic Regions / Aleutian Ridge Volcanic Arc
Ketinggian
1073 m
Koordinat
53.430, -168.130
Letusan terakhir
2008
Kondisi tektonik
Subduction zone / Intermediate crust (15-25 km)
Bentuk lahan
Shield
Batuan utama
Basalt / Picro-Basalt
Ringkasan geologi

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. More than 60 tephra layers from Okmok have been found overlying the 12,000-year-old caldera-forming tephra layer. Numerous cones and lava domes are present on the flanks down to the coast, including the SE-flank Mount Tulik, which is almost 200 m higher than the caldera rim. Some of the post-caldera cones show evidence of wave-cut lake terraces; more recent cones were formed after the caldera lake, once 150 m deep, disappeared. Eruptions have been reported since 1805 from cinder cones within the caldera, where there are also hot springs and fumaroles.

Ringkasan Wikipedia

Ringkasan Inggris

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.

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Riwayat letusan

Ringkasan (VEI dari waktu ke waktu)
Klik pada bar untuk melihat letusan individu
6310 BCE~6033 BCE · 1 letusan · VEI maks. 4210 BCE~67 · 1 letusan · VEI maks. 61731~2008 · 17 letusan · VEI maks. 46310 BCE4369 BCE2151 BCE210 BCE1731

Garis waktu rinci

  1. 2008VEI 4Teramati
    2008-07-12 – 2008-08-19
    NE caldera floor
  2. 1997VEI 3Teramati
    1997-02-11 – 1997-05-19
    SW part of caldera (Cone A)
  3. 1986VEI 2Teramati
    1986-11-18 – 1988-02-26
    SW part of caldera (Cone A)
  4. 1983VEI 2Teramati
    1983-07-08 – 1983-07-08
    SW part of caldera (Cone A)
  5. 1981VEI 3Teramati
    1981-03-24 – 1981-03-24
    SW part of caldera (Cone A)
  6. 1960VEI 3Teramati
    1960-10-15 – 1961-04-15
    SW part of caldera (Cone A)
  7. 1958VEI 3Teramati
    1958-08-14 – 1958-08-25
    SW part of caldera (Cone A)
  8. 1945VEI 2Teramati
    1945-06-04 – 1945-12
    SW part of caldera (Cone A)
  9. 1943VEI 1Teramati
    1943-06 – Berlangsung
    SW part of caldera (Cone A)
  10. 1938VEI ?Teramati
    1938 – Berlangsung
    SW part of caldera (Cone A)
  11. 1936VEI ?Perkiraan geologi
    1936 – Berlangsung
    SW part of caldera (Cone A)
  12. 1931VEI 2Teramati
    1931-03-21 – 1931-05-13
    Cone A?
  13. 1899VEI 3Teramati
    1899 – Berlangsung
    SW part of caldera (Cone A)
  14. 1878VEI 2Teramati
    1878 – Berlangsung
    Cone A?
  15. 1824VEI ?Teramati
    1824 – 1830
    Cone B?
  16. 1817VEI 3Teramati
    1817-03-01 – 1820
    Cone E? or B?
  17. 1805VEI ?Teramati
    1805 – Berlangsung
  18. 100 SM (±50 tahun)VEI 6Perkiraan geologi
    BCE 100 – Berlangsung
    Okmok II caldera
  19. 6310 SM (±500 tahun)VEI 4Perkiraan geologi
    BCE 6310 – Berlangsung

Tautan eksternal

⚠ Untuk referensi saja. Bukan untuk tanggap darurat.