Arizona hosts over 1,000 volcanoes and three active volcanic fields, the largest of which is the San Francisco Volcanic Field near Flagstaff.
These volcanic fields are considered dormant, meaning they could erupt again, but future eruptions are not expected soon. Volcanic activity in the region occurs on geological timescales, with intervals of hundreds or thousands of years between eruptions.
The most recent volcanic eruption in Arizona occurred around 1,000 years ago at Sunset Crater, a prominent cinder cone near Flagstaff. Steep-sided cinder cones form quickly during brief, explosive eruptions.
Then there are shield volcanoes, the largest type of volcano on Earth; they’re broad and convex in shape with gentle slopes. An example is the House Mountain volcano located between Sedona and the Verde Valley. Lava domes, such as Mt. Elden near Flagstaff, are circular, mound-shaped protrusions and result from slow flows of very thick lava.
Most dramatic of all is Humphreys Peak, Arizona’s highest point at nearly 13,000 feet. It’s an extinct stratovolcano with steep sides and a classic cone shape.
Arizona’s volcanic activity is rare compared to other parts of the West and most eruptions have been small and localized. Still, they have shaped the landscape with lava flows and explosive events. Beneath Arizona’s serene deserts lies a history of fiery geological forces.
This Earth Note was written by Carrie Calisay Cannon and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
