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Spurr volcano, United States
Mount Spurr, the highest peak of the Aleutian arc, is a 3374-m-high andesitic stratovolcano. During the late Pleistocene or early Holocene the volcano collapsed, creating a 5-6 km wide caldera that is breached to the south and producing a debris avalanche that traveled at least 25 km from the summit.
This 1993 view from the south looks into the breached caldera, whose rim forms the left and right skylines.
The sharp-topped, snow-covered summit (center) is a post-collapse lava dome. Crater Peak, in front of it, has been the source of frequent Holocene eruptions.
The 3374-m-high summit of Mount Spurr, the highest volcano of the Aleutain arc, is a large lava dome constructed at the center of a roughly 5-km-wide horseshoe-shaped caldera that is open to the south.
The volcano lies 130 km west of Anchorage and NE of Chakachamna Lake.
The caldera was formed by a late-Pleistocene or early Holocene debris avalanche and associated pyroclastic flows that destroyed an ancestral Spurr volcano.
The debris avalanche traveled more than 25 km to the SE, and the resulting deposit contains blocks as large as 100 m in diameter.
Several ice-carved post-caldera cones or lava domes lie in the center of the caldera. The youngest vent, 2309-m-high Crater Peak, formed at the breached southern end of the caldera and has been the source of about 40 identified Holocene tephra layers.
Spurr's two historical eruptions, from Crater Peak in 1953 and 1992, deposited ash on the city of Anchorage.
PHOTO SOURCE: Photo by Christina Neal, 1993 (U.S. Geological Survey, Alaska Volcano Observatory), courtesy of the Smithsonian National Museum of Natural History Global Volcanism Program, used with permission.
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