File:Sunset Crater & Bonito Lava Flow (upper Holocene; San Francisco Volcanic Field, Arizona, USA) (49130600663).jpg

(from park signage; original image from the United States Forest Service; north is "down" & south is "up")

This vintage aerial photo shows Sunset Crater, a cinder cone in Arizona's San Francisco Volcanic Field. Cinder cones are relatively small, steep-sided cones of loose igneous debris. They have few eruptions and a relatively large summit crater. Cinder cones are principally composed of scoria and vesicular basalt.

More than 600 eruptive centers - mostly cinder cones - are present in the volcanic field, and date from the Late Miocene to the late Holocene. The largest volcano in the area is San Francisco Mountain, an eroded stratovolcano. Cinder cones in the field have erupted a variety of igneous products, ranging from mafic to felsic to alkaline in composition - most are alkaline basalt.

Sunset Crater had an eruption in the late 11th century A.D., variously dated to 1064 or in the 1080s. The eruption involved lava flows and relatively widespread deposition of airfall scoria. This was the most recent activity in the entire San Francisco Volcanic Field.

The lava flow outlined in yellow in the photo is the Bonito Lava Flow, which occurs to the west & northwest of Sunset Crater itself. The flow covers an area about 2 to 2.5 kilometers in diameter and ranges in thickness from ~1 to over 30 meters. Flow top morphology ranges from pahoehoe to aa, but is principally slabby pahoehoe to slabby aa. The lava eruption tore away pieces of the volcano itself. Rafted cinder cone fragments of decent size occur in Bonito Flow.

Also of interest in this picture is the presence of a parking lot and hiking trail that don't exist anymore. Before 1973, tourists could hike to the summit of Sunset Crater. Because the volcano is composed of loose cinders, hiking tourists caused significant erosion and a deep gully formed. The parking lot was removed and covered with dark reddish cinders. The trace of the hiking trail is still discernible in modern satellite imagery.