Qualla: Medicine Lake Volcano: The Giant Hiding in Plain Sight

Medicine Lake Volcano: The Giant Hiding in Plain Sight: Introduction

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit Nzeemin, CC BY-SA 3.0. Most people don't know Medicine Lake Volcano exists. It has no classic cone, no steaming crater, no obvious volcanic features. It looks like gentle forested highlands in northeastern California - hills and meadows where nothing seems threatening. But Medicine Lake Volcano is the largest volcano in the Cascades by volume: 900 cubic miles of lava spread so wide it doesn't look volcanic at all. The last eruption was 950 years ago, producing Glass Mountain - a flow of obsidian so pure and sharp that chips were traded across North America by Indigenous peoples who knew good cutting tools when they found them. The volcano is dormant, not dead. Geothermal heat warms the earth. The magma chamber lurks. The gentle hills are a giant in disguise.

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Image: Nzeemin | CC BY-SA 3.0

Medicine Lake Volcano: The Giant Hiding in Plain Sight: The Hidden Giant

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit CraigCarter400, CC BY 3.0. Medicine Lake Volcano is a shield volcano - built not from explosive eruptions that create steep cones but from countless flows of fluid lava that spread wide and flat. The volcano covers 900 square miles and contains roughly 900 cubic miles of lava - more than Mount Shasta, its ...

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Image: CraigCarter400 | CC BY 3.0

Medicine Lake Volcano: The Giant Hiding in Plain Sight: The Glass

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit Daniel Mayer (talk · contribs), CC BY-SA 3.0. Glass Mountain and Little Glass Mountain are rhyolite flows on the volcano's eastern flank - obsidian so pure it glitters in the sun. The most recent eruption, 950 years ago, produced Glass Mountain: black volcanic glass covering 4 square miles to depths of 75 feet. The obsidian ...

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Image: Daniel Mayer (talk · contribs) | CC BY-SA 3.0

Medicine Lake Volcano: The Giant Hiding in Plain Sight: The Underground

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit Public domain. Medicine Lake Volcano is riddled with lava tubes - underground channels where molten rock once flowed, leaving tunnels when the surface cooled. Lava Beds National Monument, on the volcano's northern flank, contains over 700 lava tubes, more than any other area in North America. S...

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Image: Public domain

Medicine Lake Volcano: The Giant Hiding in Plain Sight: The Danger

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit Daniel Mayer, aka Mav at en.wikipedia, CC BY-SA 3.0. Medicine Lake Volcano is classified as a 'high threat' by the USGS - not because eruption is imminent but because eruption is inevitable on geological timescales, and the volcano sits near highways, powerlines, and communities. The last eruption was only 950 years ago; geological...

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Image: Daniel Mayer, aka Mav at en.wikipedia | CC BY-SA 3.0

Medicine Lake Volcano: The Giant Hiding in Plain Sight: Visiting Medicine Lake Volcano

Mon, 12 Jan 2026 00:00:00 GMT

Photo credit Chmee2, CC BY-SA 3.0. Medicine Lake Volcano is located in northeastern California, east of Mount Shasta. Medicine Lake itself is accessible via Forest Road 49 from Highway 89; the lake offers camping, fishing, and swimming in a volcanic caldera. Glass Mountain is reached via Forest Road 43; a trail cr...

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Image: Chmee2 | CC BY-SA 3.0