Upsal Hogback volcano is a tuff cone built up from phreatomagmatic eruptions that is
located near the city of Fallon, Nevada. It is composed of indurated basaltic ash and
lapilli tuff with abundant basaltic bombs. The edifice consists of the north complex (1
vent), and the south complex (3 vents). The edifice has also been severely eroded by
glacial Lake Lahontan, obscuring the original morphology of the volcano, making it look
similar to a tuff ring and not a tuff cone. Geochemical analysis of bomb samples from
Upsal Hogback show that the north and south complexes are geochemically
distinct but
still have a similar aesthenospheric mantle source. The magma supplying the volcano
originated from a spinel peridotite or low percent garnet mantle source. Neighboring
volcanic centers, Soda Lakes and Rattlesnake Hill, also have similar mantle sources and
also are volcanic types on the phreatomagmatic spectrum.