GeoSnaps - Image of the Day
Geologic snapshots capturing Arizona’s geologic setting and mining history with a picture of the day from 1 January through 31 December 2013.
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11/13/2008 | House Mountain Shield Volcano, Verde Valley, Sedona. The Sedona area is mostly known for it's colorful Permian red rocks but southwest of the city is a partially dissected shield volcano called House Mountain. The volcano was previously thought to be about 5 million years old but field relationships and more precise radiometric dating revealed that it is three times older, erupting between 15 and 13 million years ago. Shield volcanoes form when very fluid magma erupts from a central vent to create a broad pile of lava flows that resemble a warriors shield laying on its side. After its emplacement, House Mountain was completely buried in lacustrine (lake) deposits belonging to the Miocene-Pliocene Verde Formation. Downcutting by the Verde River subsequently exhumed the volcano from beneath its sedimentary veneer however, some remnant limestone still clings to the volcano's slopes. (Photo & caption by Wayne Ranney)