The Shake Up
Over two million years ago, faulting of the oceanic and continental plates within the earth’s crust caused land blocks to drop. As the Tahoe block dropped, the adjacent Sierra Nevada and Carson Range blocks uplifted to form the Lake Tahoe Basin and the Sierra Nevada and Carson Range.
Ice and Fire Form the Landscape
Giant glaciers scoured out the bottom of Lake Tahoe and deposited rock and sediment throughout the Basin. Mt. Pluto (at Northstar) erupted, creating a volcanic dam on Lake Tahoe’s northwest shore at the Truckee River. As the Basin filled with snowmelt, the dam eroded, forming modern-day Lake Tahoe and the Truckee River outlet.
Rock and Roll
Tahoe’s boulders have been cracked and pushed around for millions of years. Rocks are fractured by a freeze-thaw process where water settles in small crevices and when frozen, expands to widen the cracks. Boulders also are moved and rearranged by frost-heaves when freezing water in the soil expands, uplifting them from the ground. Look around and you will see nature at work.
Did You Know? Tahoe boulders have been moved and cracked by glaciers and freeze- and thaw-uplifting, creating balancing rocks and cracks large enough for trees to grow out of stone.
USFS Geology of the Lake Tahoe Basin
Tahoe National Forest Information Page