Blue Lake crater, one of the least known Holocene volcanoes of the Oregon Cascades, is a series of at least three overlapping explosion craters along a NE trend slightly east of the crest of the Cascade Range. Explosions through pre-existing bedrock about 1300 years ago deposited basaltic bombs and cinders and spread a tephra blanket to the east and SE during perhaps the youngest eruption in the Santiam and McKenzie Passes region. The eruption created an elongated, steep-walled crater with a low rim that rises about 50 m above adjacent topography. The crater is now filled by the 0.3 x 0.8 km wide Blue Lake, immediately west of the popular recreation area of glacial moraine dammed Suttle Lake. A chain of spatter cones 6 km to the SSW and about 4 km NE of Mount Washington, is aligned with Blue Lake crater and has ejecta that are petrographically similar to that from Blue Lake and may have been erupted at the same time.