geology & History of the lake

Geology
Although it is commonly believed that Lake Tahoe is of volcanic origin, the Lake Tahoe Basin was actually formed by geologic block faulting 25 million years ago. Uplifted blocks created the Carson Range on the east and the Sierra Nevada Range on the west. Down-dropped blocks created the Lake Tahoe Basin in between.

A lake formed in the basin between the two ranges and was originally significantly larger than modern Lake Tahoe. Several active volcanoes poured lava into the basin, eventually damming the outlet near the present town of Truckee. The waters rose to several hundred feet higher than present level. Finally, a new outlet was cut, just east of Mt. Pluto (the present location of Northstar Ski Area). Modern Lake Tahoe was shaped and landscaped by the scouring glaciers during the Ice Age (the Great Ice Age began a million or more years ago). Moraines, glacial debris left behind, blocked the outlet again, changing it to the present Truckee River outlet at Tahoe City.

History
For many centuries, Lake Tahoe was occupied only by Native American tribes. In fact, artifacts confirm the presence of the Washoe Tribe of Native Americans at Lake Tahoe over 10,000 years ago. Native Americans camped, hunted, and fished at Lake Tahoe in relative seclusion until General John C. Fremont’s exploration party “discovered” the lake in 1844.

For many years following Tahoe's discovery the area was virtually ignored. In 1859 however, the Comstock Lode was discovered in Virginia City, Nevada and during the 1860’s Tahoe became the center of a lively commerce involving the silver mines in Virginia City and the Central Pacific Railroad (which was pushing over the Sierra toward the town of Truckee). The Comstock era resulted in large-scale deforestation of the Tahoe Basin, as timber was required to build mine shafts and support growing developments. It is estimated that over 80 percent of the Basin’s forests were clear cut during this time.

Since then, public appreciation of Lake Tahoe and its natural resources has grown. Efforts were made during the 1912, 1913, and 1918 congressional sessions to designate the Tahoe Basin as a national park but were unsuccessful. Development pressures escalated again in the 1940’s and 1950’s, and a group of residents and visitors who were concerned about the environmental health of the region formed the League to Save Lake Tahoe.

Information provided by the U.S. Geological Survey and the U.S. Forest Service.