Much of northern Arizona lies in an extinct volcano area, called the San Francisco Volcanic Field. This field covers about 1,800 square miles and lies within the Coconino and Kaibab National Forests. “Almost all hills and mountains between Flagstaff and the Grand Canyon are geologically young but extinct volcanoes of the San Francisco Volcanic Field,” according to the USGS. The types of volcanoes are: active, dormant, and extinct. An active volcano has had a recent eruption (Mount St.Helen’s). A dormant volcano is not erupting now, but expected to at any time (Mount Rainier). An extinct volcano has not erupted for tens of thousands of years and are not expected to.
This area is one of reasons the terrain in northern Arizona is unique. There are hundreds of volcanoes in the San Francisco Volcanic Field, some include: Elden Mountain, Sunset Crater, Red Mountain, Bill Williams, Mountain, and the San Francisco Peaks.