As the geologic formations began to take shape, eruptions from the now-extinct volcano Mount Pluto formed a dam on the north side, as melting snow filled the southern and lowest part of the basin to form the ancestral Lake Tahoe as rain and runoff added more water to the lake.
Lake Tahoe was shaped and landscaped by scouring glaciers during the Ice Ages, which began a million or more years ago and is fed from 63 tributaries with the Truckee River as the main and only outlet.
The Truckee flows northeast through Reno, Nevada and into Pyramid Lake, which has no outlet.
The soil found on the basin come primarily from andesitic volcanic rocks and granodiorite, with minor areas of metamorphic rock.
Some of the valley bottoms and lower hill slopes are covered with glacial moraines, or glacial outwash material derived from the parent rock.
With the great depth of Lake Tahoe, as well as the locations of the normal faults within the deepest portions of the lake, suggests that earthquakes on these faults can trigger tsunamis with wave heights predicted to be around 10 to 33 ft in height, capable of traversing the entire lake in just a few minutes.
This may be evident with the massive collapse of the western edge of the basin that formed McKinney Bay around 50,000 years ago which was thought to have generated a tsunami wave with an estimated height of no less than 330 ft.
Although Lake Tahoe is a natural lake and with most areas consider protected, it is also used for water storage by the Truckee-Carson Irrigation District, for which the lake level is controlled by a dam at the Truckee River- the lake’s only outlet- at Tahoe City.
The 6 foot high dam can increase the lake's capacity by 732,000 acre/ft.
So if you think that lake Tahoe is just a vacation spot, think again, there’s more to discover in a Lake Tahoe vacation.