The Sand Mountain volcanic field consists of a group of 23 basaltic and basaltic-andesite cinder cones along a N-S line immediately west of the Cascade crest NW of Mount Washington.  Two cone alignments trending NNW and NNE intersect near the largest cinder cone, Sand Mountain.  A series of young, unvegetated lava flows originating from vents on the west side of the chain of cones were erupted primarily during a 1000-year period from about 3000-4000 years ago.  Lava flows traveled predominately to the west, blocking local drainages and forming several small lakes.  The Lost Lake cinder cone group at the north end of the chain was active about 2000 years ago.