Chiginagak

Geography & Climate

Chiginagak is located in United States, within the Alaska Peninsula Volcanic Arc of the broader North America Volcanic Regions. Situated at 57.13° N, 156.99° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. At 2,221 meters above sea level, Chiginagak rises above the surrounding terrain into montane or subalpine conditions. The elevation creates distinct ecological zones along its flanks, from forested lower slopes to exposed rocky terrain near the summit. 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

Chiginagak 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 Chiginagak, 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

Chiginagak has 3 recorded eruptions in the geological database, spanning from 1929 CE to 1998 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1971 CE, reaching VEI 2 on the Volcanic Explosivity Index. These eruptions span roughly 69 years of volcanic history. The most recent eruption in 1998 CE places this volcano within the modern era of volcanological observation.

GVP Reference Summary

The symmetrical, glaciated Chiginagak stratovolcano locatedon the Alaska Peninsula ~15 km NW of Chiginagak Bay contains a small summit crater, which is breached to the south, and one or more summit lava domes. Lava domes occur high on the NW and SE flanks of the calc-alkaline volcano. An unglaciated lava flow and an overlying pyroclastic-flow deposit extending E from the summit are the most recent eruption products, which most likely originated from a lava dome on the SE flank, 1 km from the summit. Brief ash eruptions were reported in July 1971 and August 1998. Fumarolic activity has bene reported on the NE flank, and two areas of hot-spring travertine deposition are located at the NW base near Volcano Creek.

— Smithsonian Institution, Global Volcanism Program