Ugashik-Peulik

Geography & Climate

Ugashik-Peulik is located in United States, within the Alaska Peninsula Volcanic Arc of the broader North America Volcanic Regions. Situated at 57.75° N, 156.37° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. With a summit elevation of 1,474 meters above sea level, Ugashik-Peulik is a moderately sized peak that remains accessible to hikers and researchers for much of the year. 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

Ugashik-Peulik 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 Ugashik-Peulik, 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 andesite / basaltic andesite, 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

Ugashik-Peulik has 5 recorded eruptions in the geological database, spanning from 6550 BCE to 1852 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1814 CE, reaching VEI 3 on the Volcanic Explosivity Index. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings.

Significance

With a maximum recorded VEI of 3, Ugashik-Peulik 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 5 recorded eruptions on file, Ugashik-Peulik has enough documented activity to help scientists identify patterns in its eruptive behavior.

GVP Reference Summary

The Ugashik-Peulik volcanic complex lies south of Becharof Lake and east of Upper Ugashik Lake. Late-Pleistocene caldera formation was followed by the emplacement of at least five Holocene lava domes within the 4.5-km-wide caldera. Most of the caldera walls consist of basement sandstones of Jurassic age. Following caldera formation the small, 3 km3 Peulik stratovolcano grew 2.5 km to the N. Lava flows from Peulik cover the caldera rim to the south and extend to Becharof Lake, 6 km N. A small lava dome on the E flank of Peulik was the source of a small block-and-ash flow. The summit of Peulik contains a 1.5-km-wide crater breached to the west that is partially filled by a lava dome. Debris-avalanche deposits cover a 75 km2 area to the NW. A single documented historical eruption took place from Peulik in 1814.

— Smithsonian Institution, Global Volcanism Program