EarthChem Home
Decade Home
About EarthChem
Overview
News
About DECADE
Help
Login
Data from the Global Volcanism Program of the Smithsonian Institution
Details for: Okmok
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. Photo by John Reeder (Alaska Division of Geological & Geophysical Surveys).
Volcano Number:
311290
Volcano Name:
Okmok
Country:
United States
Volcano Type:
Shield
Last Eruption:
2008 CE
Elevation:
1073m
Tectonic Setting:
Subduction zone / Intermediate crust (15-25 km)
Pop. within 100km:
4
Latitude:
53.43
Longitude:
-168.13
Details
Hide
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.
Download XLS
Eruption Data from the Global Volcanism Program of the Smithsonian Institution
Show 19 Results
Hide Results
Emissions Data from the Global Volcanism Program of the Smithsonian Institution
Show 1 Results
Hide Results
Data from the Earthchem Library
Sorry. No data exist for this volcano in the EarthChem Library.
Data from the Earthchem Portal
Sorry. No data exist for this volcano in the EarthChem Portal.
Data from the SESAR Database
Show 81 Results
Hide Results
Data from the MaGa Database
Sorry. No data exist for this volcano in the MaGa database.
Data from UNAVCO
Sorry. No data exist for this volcano in the UNAVCO database.
Data from USIEI
Sorry. This volcano is not covered by any USIEI projects
Data from IRIS FDSNWS
Show 794 Results
Hide Results