Sand Mountain Volcanic Field


The Sand Mountain volcanic field consists of a group of 23 basaltic and basaltic-andesite cinder cones and lava flows at the western margin of the High Cascades in the upper McKenzie River watershed.


The field covers 75 km2 (30 mi2) fed from two aligned groups of 42 distinct vents that trend north-northwest and north-northeast and intersect near the largest cinder cone, Sand Mountain (250 m or 820 ft high). The vent alignments suggest that a complex system of dikes exists beneath the chain. A series of lava flows originating from vents along the chain were erupted primarily from about 3,000 to 4,000 years ago. They traveled chiefly to the west, blocking local drainages and forming several small lakes. The Lost Lake cinder cone group at the north-northeast end of the chain was active about 2,000 years ago. The extensive young, highly fractured lava flows from Sand Mountain, and others from Belknap Crater, greatly disrupted the McKenzie River and create a landscape of lava-filled canyons, lakes, disappearing streams, and numerous springs.


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