Aerial view of Morale claim maar. The maar is adjacent to the southwest side of Red Clay Mesa. Photograph by George Ulrich, U.S. Geological Survey.
Morale claim maar is in center of the photo. Light colored rocks are lake deposits. Red Clay Mesa, on the right margin of the photo, is capped by a black monchiquite flow. This maar was once mined for uranium ore. Photo by Steve Mattox, 1989.
The volcanic rocks at Hopi Buttes are composed of a monchiquite, a type rock that has less silica, more water, titanium, phosphorous, and incompatible elements relative to most of alkali basalts. Monchiquite commonly lacks plagioclase but contains zeolite and feldspathoid minerals. Photo by Steve Mattox, 1989.
Some of the layers of rock that accumulated in the lake are now highly convoluted and deformed. These layers may result from slumping of sediment from the rims of the maars into the interior of the lake. An alternative hypothesis suggests that the layers were deformed when carbon monoxide gas was released catastrophically. The 1986 eruption at Cameroon is a modern example of this type of degassing. Photo by Steve Mattox, 1989.
Ulrich, G.E., Condit, C.D., Wenrich, K.J., Wolfe, W.E., Holm, R.F., Nealey, L.D., Conway, F.M., Aubele, J.C., and Crumpler, L.S., 1989, Excursion 5A: Miocene to Holocene volcanism and tectonism of the southern Colorado Plateau, Arizona, in Chapin, C.E., and Zidek, J., eds., Field excursions to volcanic terranes in the western United States, Volume 1: Southern Rocky Mountain region: New Mexico Bureau of Mines & Mineral Resources, p. 1-41.
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