Malheur Lake - Geology

Geology

Malheur Lake is a remnant of a much larger Pleistocene lake that drained east to the Malheur River, a tributary of the Snake River. The size of this ancient lake, which existed during a wetter climate, has been estimated at 900 square miles (2,300 km2), with a maximum depth of 35 feet (11 m). Its outlet was originally a channel near Princeton, but lava flows diverted the water to a gap near Crane. Much of the original lake bottom has since turned into desert or become meadows periodically watered by lake overflows. Mud Lake and Harney Lake are also remnants of the original pluvial lake.

The lakes as well as nearby marshes and playas are part of Harney Basin. The basin, a closed depression, covers 5,300 square miles (14,000 km2), which makes it larger than the state of Connecticut.