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Okmok volcan

Mise à jour: 5 déc.. 2022 17:08 GMT -
Central shield complex with nested caldera 1073 m (3520 ft)
Fox Islands, Aleutian Islands, USA, 53.4°N / -168.17°W
Condition actuelle: normal / en sommeil (1 sur 5)
Last update: 10 déc. 2021 (changes in ground deformation pattern)

Okmok is one of the most active volcanoes in the Aleutian island chain (Alaska). It consists of a complex of shields truncated by a caldera and several active vents inside the caldera, which have built small cones and lava flows.

Montrer carte interactive
Style éruptif tipique: Explosive and effusive
Eruptions du volcan Okmok: 1817, 1824, 1878(?), 1899, 1931, 1935, 1936, 1938, 1943, 1945, 1958, 1960, 1981, 1983, 1986, 1997, 2008

Derniers séismes proches

HeureMag. / ProfondeurDistance/Lieu
vendredi, 2 décembre 2022 GMT (1 séisme)
2 déc. 2022 02:35 (GMT -9) (2 déc.. 2022 11:35 GMT)
0.3

7.3 km
2.4 km (1.5 mi)
68 Km NE of Nikolski, Alaska

Introduction

Okmok's caldera was formed by at least two collapses following catastrophic pyroclastic eruptions, at around 8200 y B.P. and 2400 y. B.P.
Within the caldera, the oldest volcanic deposits are brecciated pillow lavas and pyroclastic rocks once deposited in a caldera lake. The lake attained a maximum depth of about 150 m and the upper surface reached an elevation of about 475 m, at which point it overtopped the low point of the caldera rim. A small shallow lake near the outlet of the caldera is all that remains today. Three dissected tuff cones may have been produced by eruptions beneath the former caldera lake. Other cinder cones occur atop pillow lavas; such cones apparently breached the surface of the former lake. Cinder cones and associated lava flows that are younger than the caldera lake are identified by structures and textures characteristic of subaerial eruption. The documented eruption of 1945 occurred at a cinder cone near the southwest caldera wall; this cone may have been the site of all historical activity of Okmok volcano. Hot springs and fumaroles occur both within Okmok caldera and at Hot Springs cove, 20 km to the southwest.
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Source: Alaska Volcano Observatory


See also: Sentinel hub | Landsat 8 | NASA FIRMS
ven., 10 déc. 2021, 03:57

Okmok volcano (Aleutian Islands, USA): changes in ground deformation pattern

A long-term ground deformation change has been detected at the volcano by Global Navigation Satellite Systems (GNSS) stations during September and November. ... Read all
mer., 18 mars 2009, 06:00

Okmok volcano (Fox Islands, USA) - Smithsonian / USGS Weekly Volcanic Activity Report for 18 March-24 March 2009 (Continuing Activity)

On 20 March, AVO lowered the Volcano Alert Level for Okmok to Normal and the Aviation Color Code to Green. Seismic activity had been at low to near background levels and satellite views showed no activity during the previous two weeks. The last confirmed ash emission at Okmok occurred on 19 August 2008. ... Read all
map showing location of Mount Okmok. Image source: Cameron, Cheryl, courtesy of the Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys
map showing location of Mount Okmok. Image source: Cameron, Cheryl, courtesy of the Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys
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