A Little Geology of Lake Tahoe

Ever wonder how this beautiful landscape of Tahoe came to be? Here is a little geology lesson of Lake Tahoe:

The Lake Tahoe basin was formed by normal faulting about 2 to 3 million years ago. A geologic fault is a fracture in the Earth’s crust that causes blocks of land to move up or down. Normal faulting occurs when a ‘block’ of land falls down relative to the other (non-moving) block. This down-dropping of blocks is how the Tahoe Basin was originally formed. In this case, uplifted blocks of land created the Carson Range to the east of Tahoe, and the Sierra Nevada Range on the west.

After the basin was formed, snow rain and mountain streams filled the southern and lowest part of the basin. This was the ancestor to our modern Lake Tahoe! The basin became blocked off due to the volcanism of Mt. Pluto which is the present location of Northstar ski resort. The landscape was then further shaped by glaciers during the last ice age (less than 1 million years ago). Emerald Bay, Fallen Leaf Lake and Cascade Lake were all carved out during this glaciation. Today, many small streams (63) flow into the lake, but the Truckee River is the only river that drains out of the lake. This river doesn’t flow to the ocean like most other large bodies of water – rather it flows northeast through Reno and drains into Pyramid Lake in Nevada.

If you have jumped into Tahoe any time of the year, you know that it is sometimes shockingly cold. In the summer, shallow areas can be around 60 degrees (bearable for swimming). But below 600 feet, the temperature hovers around 39 degrees Fahrenheit! One reason this lake is so unique, is the water clarity. In some places you can see 70 feet below the water surface! How is the lake so clear you ask? 40% of the precipitation that falls in the basin falls directly into the lake (minimizing soil runoff). The rest of the water entering Lake Tahoe is filtered through marshes and meadows. This clarity is also the reason the color is so spectacularly blue! Want to learn more about Tahoe’s changing clarity? Learn about ways to help with The League to Save Lake Tahoe (Keep Tahoe Blue)

Here are some cool Lake Tahoe facts:

Second deepest lake in the US, with a max depth of 1,645ft (second to Crater Lake at 1949 ft)
Tenth deepest lake in the world!
Diameter north to south: 22 miles
Diameter east to west: 12 miles
The shoreline length is 75.1 miles and the encircling state highway is 71.8 miles long.
Average surface elevation: 6,225 ft above sea level
Highest peak in the basin: Freel Peak at 10,891 feet
About 1/3 of Tahoe basin is in Nevada, 2/3 are in California
The water in Lake Tahoe could cover California in 14 inches deep water