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Aerial view of obsidian (rhyolite) lava flow on Medicine Lake Volcano and Mt. Shasta, northern California (140617-161)
Conchoidal fracture in Mahogany obsidian hand sample. (140429-9)
Students inspect vitrophyre (black glassy zone) in the 9.5 Ma Rhodes Tuff of SE California. (140427-61)
Aerial of Mt. St. Helens and crater with lava dome, 2014, Washington. (140221-118)
Eocene age lahar (volcanic mudflow) in the western Cascades of Oregon.
Colonnade–columnar jointing– in Picture Gorge Basalt, of the Columbia River Basalt Group, Oregon (110806-17)
Pumice deposit at Crater Lake in Oregon. Differently colored pumice from differences in iron-oxide content (Image ID# 5d-8638)