Sunset Crater is the youngest of the cinder cones of the active San Francisco volcanic field of northern Arizona. Sunset erupted about 950 years ago and displaced nearby Native American people. The reddish color at the summit is the result of oxidation of tephra - ash, cinders and bombs - erupted from the vent. In the foreground is an older cinder cone mantled with black ash from Sunset Crater. Sunset Crater is now part of Sunset Crater National Monument - a tourist favorite. Of the more than 600 volcanoes in the field, Sunset is the only one off limits to hikers.
AZGS thanks photographer Ted Grussing for the use of this image.