Lake Lahontan was a vast endorheic lake in the Pleistocene that covered much of northwestern Nevada and extended into northeastern California and southern Oregon. Reaching its greatest extent about 12,700 years ago, it spanned more than 8,500 square miles and was one of North America's largest lakes. As the climate warmed, evaporation increased and by about 9,000 years ago the lake had largely broken into smaller lakes, leaving playas such as the Black Rock Desert, Carson Sink, and Humboldt Sink, while Pyramid Lake and Walker Lake remained. Its former shorelines, preserved in tufa formations, record Ice Age climate change and the lake's major role in Great Basin natural history.