Lake Tahoe was formed by the rise and fall of the landscape due to faulting 25 million years ago. The bottom of the lake was once a valley basin (open to the north) and home to two parallel faults, hence the eastern and western mountains. Lava flowing from Mt. Pluto on the north shore created a barrier across the basin’s only outlet and water from rivers and streams then filled the lake. During the Ice Age, glaciers formed in the surrounding mountains, leaving broad U-shaped valleys including Cascade Lake, Fallen Leaf Lake and, the most well known, Emerald Bay.
How big is the lake?
12 miles wide by 27 miles long, 77 miles around (over three hour to drive) with 72 miles of shoreline. It is 1,645 feet at its deepest point (approximately five and a half football fields).
Fun fact: Eight feet off the shore at Rubicon Point, one could drop the Empire State Building into the lake and then stack the Washington Monument on top of it and the two would be completely immersed in water with 20 feet to spare.
How much water is in the lake?
37 trillion gallons, fed by 63 streams.
Fun fact: The amount of water that evaporates from the lake daily is enough water to supply a city the size of Los Angeles with water for five days.
Fun fact: If the lake were drained, there would be enough water to cover the state of California with 14 inches of water, or the state of Texas with 8.5 inches of water.
Fun fact: If the Panama Canal were built all the way around the equator, the water from the lake could fill it with enough left over to fill a second canal from New York City to San Francisco.
Where does all that water go?
The lake’s only outlet is the Truckee River, which flows east to Pyramid Lake in Reno and never reaches the ocean.
How cold and pure is the water?
Average temperature on the surface is 61 degrees and never varies more than three degrees. Below 600 feet the temperature drops to a frigid 39 degrees. The lake water is 99.7% pure, which is cleaner than the drinking water in most U.S. cities.
Fun fact: In optimum conditions, one can drop a rock in the lake to a depth of 125 feet and still see it clearly.
Why is the water so pure?
40% of the lake’s volume is precipitation falling directly into the lake. The soil composition around the lake works as an ideal filtration system for all other precipitation and snow melt.
Does the lake ever freeze?
There are spots around the shore and around Emerald Bay that do ice over, but the rest of the lake is too deep and has too much continual motion to freeze over.
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