|
 How
Was The Lake Formed?
Several geological incidents millions of year ago
resulted in the famous blue and green waters of Lake Tahoe.
The Lake Tahoe Basin was formed by faulting
(fractures in the earth’s crust allowing blocks of land to rise
and sink) occurring over several million years. A fault on the
eastern margin created the Carson Range, while the Sierra Nevada
rose out of a shallow sea on the western side.
From the “up-thrown” fault blocks rose to the
highest peaks in the Tahoe Basin. A lake formed near the
southern and lowest part of the basin, fed by snow, rain and
rivers. The lake rose until it found an outlet near the present
town of Truckee.
Several active volcanoes poured lava into the
basin, eventually damming the outlet, and then the waters rose
again, several hundred feet higher than the present level. A new
outlet was cut, east of Mount Pluto (the present location of
Northstar). Rivers of ice followed the V-shaped stream canyons,
carving them, as they moved downward, to smooth U-shaped
valleys.
Why is the water so clear?
The Tahoe Basin is mostly granite, with little
topsoil, and therefore few nutrients have washed into the lake
to promote the growth of algae and other organisms that make
water murky.
As well,
40 percent of the precipitation falling into the
Lake Tahoe Basin, lands directly on the lake. The remaining
precipitation drains through the decomposed granitic soils found
in marshes and meadows, creating a good filtering system for
water.
The
colors of Lake Tahoe vary according to the water’s depth. The
bluer the water, the deeper it is. The more shallow the water,
the greener the color becomes.
Where does the water go?
The Truckee River is Tahoe’s only outlet and
flows from the dam in Tahoe City east through Reno and
eventually drains into Pyramid Lake in the Nevada desert. From
there, it evaporates back into the atmosphere.
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