South of the Chiricahua Mountains lies the Quaternary San Bernardino volcanic field. The field comprises mostly basaltic cinder cones, lava flows, tuff rings, and several maar volcanoes. This unnamed maar crater - flat-bottomed depression in the center of the view - is surrounded by a tuff ring consisting of pyroclastic surge and tuff deposits. For three geologic map plates and a 21-page report, see Biggs and others (1999); http://repository.azgs.az.gov/uri_gin/azgs/dlio/204 .
NOTE: By definition the base of a maar volcano is excavated into the existing substrate. This appears to be the case here, but it's unclear if pre-existing substrate is exposed. In which event, it might be prudent to refer to it as a tuff ring, which does require excavation of existing substrate.
View courtesy of Google Earth