Sunset Crater is a cinder cone located north of Flagstaff in the U.S. state of Arizona. The crater is within the Sunset Crater Volcano National Monument.
Sunset Crater from the Cinder Hills
A cinder cone is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that often is symmetrical; with slopes between 30 and 40°; and a nearly circular ground plan. Most cinder cones have a bowl-shaped crater at the summit.
Cross-section diagram of a cinder cone or scoria cone
Cinders at a cinder cone in San Bernardino Valley, Arizona
SP Crater, an extinct cinder cone in Arizona
Sunset Crater, a young monogenetic cinder cone in Arizona that began forming around the year 1075 CE