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North Sister's steep NE face, thick summit lava flow makes up "Glis...

1905 (approx.)

Detailed Description

Remnant of Villard Glacier is in cirque below. Thick summit lava flow makes up "Glisan Pinnacle," which overlies hundreds of thin rubbly lava flows that are intercalated with red-oxidized agglutinate and scoria falls exposed on 800-m- (2600-ft-) high face below. Flows that form ridge at upper right are thicker than those on most of edifice. Ash-rich phreatomagmatic fallout layers in lowest 150 m (500 m) are pervasively altered to yellow-orange clay-like material and riddled with dikes, many of which also cut through overlying stack of thin lava flows.