Bogoslof

Geography & Climate

Bogoslof is located in United States, within the Aleutian Ridge Volcanic Arc of the broader North America Volcanic Regions. Situated at 53.93° N, 168.03° W in the Northern Hemisphere, the volcano lies within a temperate climate zone. At just 150 meters above sea level, Bogoslof 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 composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Bogoslof 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 Bogoslof, 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 trachyandesite / basaltic trachyandesite, 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.

Eruption History Summary

Bogoslof has 12 recorded eruptions in the geological database, spanning from 1796 CE to 2016 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 2016 CE, reaching VEI 3 on the Volcanic Explosivity Index. Notable eruptions include 2016 CE (VEI 3), 1992 CE (VEI 3), 1906 CE (VEI 3). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. With eruptive activity as recently as 2016 CE, Bogoslof remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 3, Bogoslof has produced eruptions capable of generating pyroclastic flows and significant ash fall in the surrounding area. While not among the largest eruptions globally, VEI 3 events pose serious hazards to local populations and can disrupt regional air travel. With 12 recorded eruptions, Bogoslof has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the North America Volcanic Regions region. Given its recent activity, Bogoslof is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Bogoslof is the emergent summit of a submarine volcano that lies 40 km N of the main Aleutian arc. It rises 1,500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits by exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. The small Fire Island (New Bogoslof), about 600 m NW of Bogoslof Island, is a remnant of a lava dome formed in 1883.

— Smithsonian Institution, Global Volcanism Program