USGS Science in the Lake Tahoe Basin

Interesting Facts about Lake Tahoe

Lake Tahoe is the second deepest lake in the United States and the tenth deepest in the world, with a maximum depth measured at 1,645 ft (501 m) and an average depth of 1,000 ft (305 m). Crater Lake in Oregon is the deepest lake (1,949 ft or 594 m) in the United States. According to the Tahoe Environmental Research Center State of the Lake Report 2017, some interesting facts about Lake Tahoe include:

  • Lake surface area: 191 mi2 (495 km2)
  • Length: 22 miles (35 kilometers)
  • Width: 12 miles (19 kilometers)
  • Length of shoreline: 75 miles (120 kilometers)
  • Volume of water: 39 trillion gallons
  • Length of time it would take to refill the lake: about 600 years
  • Lake clarity 2016 (annual average Secchi depth): 69.2 ft
  • Number of large lakes worldwide with annual clarity exceeding Tahoe’s: 0

The water temperature near the surface generally cools to 40-50°F (4.5-10°C) during February and March and warms to 65-70°F (18-21°C) during August and September. Below a depth of 600-700 ft (183-213 m), the water temperature remains a constant 39°F (4.0°C).

The daily evaporation from Lake Tahoe (half a billion gallons) would meet the daily water needs of 5 million Americans.

The floor of the Lake Tahoe Basin is at an elevation of about 4,580 ft (1,396 m), which is lower than the surface of the Carson Valley to the east! With an average surface elevation of 6,225 ft (1,897 m) above sea level, Lake Tahoe is the highest lake of its size in the United States.

How was Lake Tahoe formed?

The Lake Tahoe Basin was formed by geologic block (normal) faulting about 2-3 million years ago. A geologic block fault is a fracture in the Earth's crust causing blocks of land to move up or down. The Carson Range on the east and the Sierra Nevada on the west represent uplifted blocks of land; the Lake Tahoe Basin in-between the Carson Range and Sierra Nevada represent a down-dropped block of land. Some of the highest peaks of the Lake Tahoe Basin that formed during this process include:

  • Freel Peak at 10,891 ft (3,320 m)
  • Monument Peak at 10,067 ft (3,068 m) (the present Heavenly Valley Ski Area)
  • Pyramid Peak at 9,983 ft (3,043 m) (in the Desolation Wilderness)
  • Mt. Tallac at 9,735 ft (2,967 m)

Snow, rain, and streams filled the southern and lowest part of the basin, forming the ancestral Lake Tahoe. 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). Many streams flow into Lake Tahoe, but the lake is drained only by the Truckee River, which flows northeast through Reno and into Pyramid Lake in Nevada.

Mt. Tallac. Photo courtesy of Timothy G. Rowe.