Redoubt

Geography & Climate

Redoubt is located in United States, within the Alaska Peninsula Volcanic Arc of the broader North America Volcanic Regions. Situated at 60.48° N, 152.74° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. At 3,108 meters above sea level, Redoubt 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

Redoubt 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 Redoubt, 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

Redoubt has 99 recorded eruptions in the geological database, spanning from 9310 BCE to 2009 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 2009 CE, reaching VEI 3 on the Volcanic Explosivity Index. Notable eruptions include 2009 CE (VEI 3), 1989 CE (VEI 3), 1967 CE (VEI 3). With an average interval of roughly 114 years between eruptions over a span of 11,319 years, this is one of the more frequently active volcanoes in the database. This persistent activity suggests a robust and well-supplied magma system beneath the volcano. With eruptive activity as recently as 2009 CE, Redoubt remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 3, Redoubt 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. Its 99 recorded eruptions make it one of the most prolific volcanoes in the entire global volcanic record, reflecting an exceptionally persistent magma supply system that has sustained near-continuous eruptive activity over millennia. Given its recent activity, Redoubt is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

Redoubt is a glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano was constructed beginning about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit 13,000-10,500 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3,500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.

— Smithsonian Institution, Global Volcanism Program