The San Francisco volcanic field of northern Arizona covers nearly 3,000 sq. miles and includes 600 cinder cones (the small pimple-like features), 10 silicic domes (e.g., Mt Elden, Kendrick Peak), and the San Francisco Mountain composite volcano - the largest volcano in the field, and at 12,666 feet above sea level, the highest point in Arizona.
About 6 million years ago, volcanic activity began in the western part of the field. In fits and starts, the locus of volcanism has migrated eastward. About 950 years ago, Sunset Crater, the youngest cinder cone in the field, erupted several miles east of San Francisco Mountain. Small volume basaltic lava fields like the San Francisco field erupt infrequently every several thousand years. This is an active volcanic field and we anticipate future eruptions in the eastern part of the field.
(Digital Elevation Model (DEM) courtesy of NASA.)