The answer to whether there are volcanoes in Idaho is definitively yes. The state’s landscape is a testament to an expansive, long-lived volcanic history, containing one of the most remarkable volcanic provinces in North America. This activity, spanning millions of years, has shaped the land, leaving behind massive lava fields and the remnants of colossal ancient eruptions. The evidence of this fiery past is preserved across the state in unique landforms.
The Snake River Plain Volcanic Field
The most obvious sign of this past volcanism is the Snake River Plain (SRP), a vast arc-shaped depression that stretches approximately 400 miles across southern Idaho. This geological feature ranges from 50 to 125 miles in width, with the concave side facing north. The plain itself is a massive volcanic plateau formed by extensive outpourings of basaltic lava. This lava is relatively fluid and produces low-relief landscapes, often sitting atop much older, more explosive volcanic deposits. The eastern portion of the plain results from the passage of the North American Plate over a stationary heat source deep within the Earth.
Craters of the Moon National Monument
Idaho’s most recent and famous volcanic activity is preserved at Craters of the Moon National Monument and Preserve, a landscape that resembles a desolate lunar surface. This area’s lava fields were created during eight major eruptive periods that occurred between 15,000 and about 2,000 years ago. The eruptions came from the Great Rift, a linear fissure system stretching over 50 miles long.
The monument is covered by over 60 distinct lava flows and features more than 25 volcanic cones, including the prominent Big Cinder Butte. Specific features like the Kings Bowl and Wapi lava fields were formed during the most recent eruptive cycle approximately 2,200 years ago. Other remnants of this basaltic volcanism include extensive lava tubes, spatter cones, and ropy pahoehoe lava.
The Yellowstone Hotspot Geological History
The driving force behind Idaho’s volcanism is the Yellowstone Hotspot, a plume of superheated rock rising from the deep mantle. Over the past 16 to 17 million years, the North American tectonic plate has slowly moved southwest over this fixed heat source. This movement created a distinct trail of progressively younger volcanic activity stretching across the Snake River Plain toward the hotspot’s current location in Yellowstone National Park.
The older, western part of the track consists of remnants of massive, explosive rhyolite eruptions that formed colossal calderas. For instance, the Heise volcanic field in eastern Idaho experienced caldera-forming eruptions that began around 6.6 million years ago. These high-silica rhyolite eruptions were distinct from the later, more fluid basalt flows that partially covered them to form the surface of the Snake River Plain.
Assessing Idaho’s Current Volcanic Risk
Idaho’s volcanic fields are not extinct and still pose a measurable, though relatively low, risk of future eruptions. The Craters of the Moon area is classified as dormant, not extinct. The time between its past eruptive events averaged around 2,000 years, and it has been approximately 2,100 years since the last major event. This suggests that future activity, most likely effusive fissure eruptions of basaltic lava, is possible on a geological timescale.
The United States Geological Survey (USGS) monitors this region as a member of the Yellowstone Volcano Observatory (YVO) consortium, which includes the Idaho Geological Survey (IGS). Monitoring efforts track signs of volcanic unrest, such as increased seismicity and ground deformation, which could indicate magma movement beneath the surface. For areas near the youngest volcanic fields, the volcanic hazard is classified as medium, meaning a potentially damaging eruption has occurred within the last 10,000 years and future events are possible.