English: Pumice from the Holocene of Oregon, USA.

Crater Lake is a large, deep, freshwater lake in the Cascade Range of America's Pacific Northwest. It formed about 7,700 years ago when an ancient volcano called Mt. Mazama had an enormous explosive ash eruption. The eruption was followed by collapse of the mountain, leaving a large depression which later filled with water. Large holes or depressions formed when a volcano destroys itself or collapses are called calderas. Crater Lake Caldera in Oregon is a world-class example of this type of volcanic feature.

Seen here is a rhyodacitic pumice sample from a roadcut about 27 air-miles northwest of the caldera. It was deposited by a pyroclastic flow during Mazama's 7.7 ka eruption.

Age: early Holocene (~7550 to 7760 years ago)

Locality: roadcut along the southern side of Route 138 (= North Umpqua Highway), just southeast of the town of Clearwater, eastern Douglas County, western Oregon, USA (43° 15’ 28.02” North latitude, 122° 24’ 51.93” West longitude)