Geology and Physiography of the Pribilof Islands

This page was written by Jeanette Wolak and Erin Klauk as part of the DLESE Community Services Project: Integrating Research in Education.

St. George Island Village, Pribilof Islands, Alaska. Details

The Pribilof Islands are located approximately 250 miles (400 km) north of the Aleutian Arc on the southern edge of the Bering Sea shelf (57°N, 107°W). The islands formed via basaltic lava flows which erupted onto the Pribilof Ridge, a structural arch that trends north-northwest and parallels the shelf-break (Barth, 1956 ; Winer et al., 2004 ). The two largest, inhabited Pribilof islands include St. George and St. Paul.

The islands are considered part of the Bering Sea Basalt Province (BSBP), a group of ~ 15 late Cenozoic basaltic volcanic fields that are widely distributed in the Bering Sea region and along the western margins of mainland Alaska (Wirth et al., 2002 ; Winer et al., 2004 ). These types of volcanoes are commonly referred to as 'intraplate volcanoes' because they occur far from plate tectonic boundaries. In the case of the BSBP, volcanism occurs within the North American Plate, laterally distal from the boundary with the Pacific Plate to the south.

St. George Island is the older of the two principle Pribilof Islands. Radiometric dating of St. George lava flows yield ages of approximately 2.2—1.6 million years old (Cox et al., 1966 ). Lava flows on St. Paul Island are significantly younger and range in age from 540,000—3,230 years old (Winer et al., 2005 ). The ages of volcanism on Otter Island and Walrus Island, the two smallest, uninhabited Pribilof Islands, are currently unknown.

The topography of the islands ranges from smooth, sloping shield volcanoes like Bogoslof Hill (St. Paul Island) to steep, highly-eroded vertical cliffs like the High Bluffs (St. George Island).

To further investigate the geology and physiography of the Pribilof Islands, check out the links below:

Geology of the Pribilofs

Resources containing information about the geology of the Pribilof Islands, Alaska.

Geologic Maps of The Pribilofs

Resources containing geologic map information for the Pribilof Islands, Alaska.

Physiography of the Pribilofs

Resources containing information about the physiography of the Pribilof Islands, Alaska.

For ideas on how to use these webpages in a classroom, a Study Guide is provided.