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The
Lake Tahoe Basin was formed by geologic block (normal) faulting
about 2 to 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. Uplifted blocks created the Carson Range
on the east and the Sierra Nevada on the west. Down-dropped
blocks created the Lake Tahoe Basin in between. Some of the
highest peaks of the Lake Tahoe Basin that formed during this
process were 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),
and 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.
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), 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.
Please Note: The depth of Lake Tahoe changes every
day as the lake level changes. The deepest measurement from
the 1998 bathymetric survey was 1,637 ft (499 m) deep. The
depth of Lake Tahoe depends on the height it is measured from;
some measurements use sea level as a base reference, others
use different points of reference. The appropriate reference,
or datum, for Lake Tahoe's depth is still being debated. Therefore
the measured depth of a lake is only preliminary data and
may change.
Lake Tahoe is about 22 mi (35 km) long and l2 mi (19 km) wide
and has 72 mi (116 km) of shoreline and a surface area of
191 mi2 (495 km2). 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.
The water in Lake Tahoe could cover a flat area the size of
California 14 in (36 cm) deep. This amount of water is enough
to supply everyone in the United States with 50 gallons of
water per day for 5 years. The amount of water that evaporates
from the surface of Lake Tahoe every year could supply a city
the size of Los Angeles for 5 years.
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