Medicine Lake

Geography & Climate

Medicine Lake is located in United States, within the High Cascades Volcanic Arc of the broader North America Volcanic Regions. Situated at 41.61° N, 121.55° W in the Northern Hemisphere, the volcano lies within a temperate climate zone. At 2,412 meters above sea level, Medicine Lake 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 shield, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Medicine Lake 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 Medicine Lake, 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.

Eruption History Summary

Medicine Lake has 10 recorded eruptions in the geological database, spanning from 3190 BCE to 1910 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1060 CE, reaching VEI 3 on the Volcanic Explosivity Index. Notable eruptions include 1060 CE (VEI 3), 1010 CE (VEI 3). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. The most recent eruption in 1910 CE places this volcano within the modern era of volcanological observation.

Significance

With a maximum recorded VEI of 3, Medicine Lake 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 10 recorded eruptions, Medicine Lake has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the North America Volcanic Regions region.

GVP Reference Summary

Medicine Lake is a large Pleistocene-to-Holocene, basaltic-to-rhyolitic shield volcano east of the main axis of the Cascade Range. Volcanism, similar in style to that of Newberry volcano in Oregon, began less than one million years ago. A roughly 7 x 12 km caldera truncating the summit contains a lake that gives the volcano its name. A series of young eruptions lasting a few hundred years began about 10,500 years before present (BP) and produced 5 km3 of basaltic lava. Nine Holocene eruptions clustered during three eruptive episodes at about 5000, 3000, and 1000 years ago produced a chemically varied group of basaltic lava flows from flank vents and silicic obsidian flows from vents within the caldera and on the upper flanks. The last eruption produced the massive Glass Mountain obsidian flow on the E flank about 900 years BP. Lava Beds National Monument on the N flank of Medicine Lake shield volcano contains hundreds of lava-tube caves displaying a variety of spectacular lava-flow features, most of which are found in the voluminous Mammoth Crater lava flow, which extends in several lobes up to 24 km from the vent.

— Smithsonian Institution, Global Volcanism Program