Existing comment:
An Ancient Lake Endures:
A Fiery Past:
We can data Mono Lake's age by the Long Valley eruption, 760,000 years ago. When the volcano erupted 15 miles to the south, it deposited a thick layer of ash over the Mono Basin. Drilling on Paoha Island, the big island in the middle of Mono Lake, revealed continuous lake sediments above a thick layer of Bishop Tuff, the ask from the Long Valley eruption. We know Mono lake to be at least as old as this explosion, making it one of the oldest permanent lakes in North America.
Local volcanic activity altered the size and shape of Mono Lake. About 300 years ago, magma pushed lake-bottom sediments above the lake's surface, forming Paoha Island. This new island displaced water and raised the lake's level.
An Icy Past:
Alternating periods of glaciation and warming have also raised and lowered Mono Lake's level throughout its existence. Thousands of years in the past, Mono Lake became an inland sea that was hundreds of feet high and five times larger than it is today. Several glaciers moved down the steep Sierra canyons and ended in carving the lake. Imagine gigantic icebergs falling off the rim of a glacier and floating wherever the wind blew them across the lake's vast surface. |