Tlevak Strait-Suemez Island

Geography & Climate

Tlevak Strait-Suemez Island is located in United States, within the Queen Charlotte Volcano Group of the broader North America Volcanic Regions. Situated at 55.25° N, 133.30° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. At just 50 meters above sea level, Tlevak Strait-Suemez Island is a relatively low-elevation volcanic feature. Despite its modest height, it remains an active geological formation with the same underlying magmatic processes as its taller counterparts. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Tlevak Strait-Suemez Island sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in United States near Tlevak Strait-Suemez Island, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

GVP Reference Summary

Scattered flat-lying lava flows with pahoehoe surfaces occur near Tlevak Strait and on the SW end of Suemez Island near the southern end of the SE Alaska panhandle. Outcrops are located on western Prince of Wales Island, along Bobs Bay on the NW side of Dall Island, and at Trocadero Bay on Suemez Island. The flows overlie Paleozoic sedimentary rocks and are associated with Tertiary rhyolitic and dacitic lava flows on Suemez Island. The younger alkaline olivine basaltic flows were considered by Brew (in Wood and Kienle, 1990) to be of probable postglacial age. The Alaska Volcano Observatory notes that "Many of the vents are located close to Cape Felix, on the southwest portion of Suemez Island. (Kate Bull, personal communication, 2009)."

— Smithsonian Institution, Global Volcanism Program