What’s the geological backstory behind your favorite alpine lake? Was it formed by glaciers, volcanoes, tectonic shifts, or all the above?
About 25 million years ago, the Sierra Nevada range, home to Big Blue, was created by tremendous uplifting of the Earth’s crust. The valley that later became the Tahoe Basin sank between two parallel faults as the mountains on either side rose – those mountains being the Sierra Nevada to the west and Carson Range to the east.
Lava flowing from a volcanic eruption of Mt. Pluto on the north shore formed a barrier or dam across the Basin’s original outlet. Water from rivers and streams flowed into the Basin, gradually filling it several hundred feet above its present level.
