San Luis State Park Geology

San Luis State Park features an 890 surface-acre playa lake, with water levels stabilized as in a reservoir, amid rolling sandhills and alkaline flats of San Luis Valley. The park is covered by Recent parabolic deflation dunes overlying Pliocene and Pleistocene outwash fan deposits. Pleistocene glaciation represents the last major geologic event. Outwash from melting glaciers was deposited across the valley floor and many large playas were created. The park occupies a rift valley that escaped the Tertiary uplifts of the Sangre de Cristo Mountains. The valley created by both rift faulting and a graben which sank as the mountains rose.