Sierra History
The Sierra Nevada region has a long and complex geologic history. The
granite rock formations that are now prevalent throughout the region formed
at least 100 million years ago as molten lava. Over the millennia, this
molten material crystallized below the surface of the overlying land surface
and formed solid rock formations far below ground.
Some 70 million years ago uplifts formed the Coast Ranges and forced
the ancestral Sierra Nevada to tilt and gently slope westward. This gradual
sloping of the range allowed subsequent erosion to expose the brilliant
granite formations that were hidden underground. Throughout the ages many
uplifts occurred and distinct faults developed. The Lake Tahoe Basin was
formed by the rising and falling of two parallel faults; the Sierra Nevada
on the western margin of the Lake and the Carson Range on the eastern
margin of the Lake.
Volcanic activity also played a major role in shaping the landscape of
the Sierra Nevada region. Ancient surface flows deposited a tremendous
amount of volcanic materials that came to rest and cooled on the surface
of the land. Subsequent uplifting thrust these volcanic peaks up to their
present day heights. Squaw Peak, high above the Siberia Express chairlift,
is an example of volcanic material leftover from the ancient volcanic
activity. Although similar in chemical composition to the granitic rock
type, volcanic rock is darker in appearance and more prone to erosion
than granite.
Glaciation is another geologic phenomenon that is visible throughout
the region. During extended ice ages, numerous glaciers formed in the
Sierra Nevada and carved and polished the world famous rock formations
common to Yosemite National Park. Although not as dramatic as in Yosemite,
glaciation occurred in and around the Lake Tahoe area and formed broad
u-shaped valleys that eventually filled in with water. Shirley Lake, Fallen
Leaf Lake and Cascade Lake are all examples of water-filled valleys carved
by glaciers. Receding glaciers here in Squaw Valley deposited much of
the material that makes up the fertile valley floor.
Squaw Valley Geology
Much
of what makes Squaw Valley USA so exciting
to ski and snowboard are the many steep and
jagged rock formations and peaks that resulted
from the region’s geologic history. To the north, Granite Chief
Peak (9050 ft.), Squaw Valley’s highest
peak, is a great example of the light gray,
medium to coarse-grained granite rock type
that is
conspicuous throughout the Sierra Nevada Mountains.
Granite is primarily composed of two light-colored
minerals, quartz and feldspar. Some granite
appears to be salt and pepper in appearance
due to the presence of darker
colored minerals such as iron and magnesium.
To the south, Emigrant Peak (8,700 ft.) and Squaw Peak (8,900 ft.) are
darker in appearance than Granite Chief Peak and are volcanic in origin.
Although similar in height, these volcanic peaks are actually quite a
bit younger in age than the other granite peaks are also less dense than
their granitic counterparts. Volcanic peaks are much more prone to erosion
than granite peaks but yield a very similar chemical composition to granite.
Riders
on Squaw Valley’s Cable Car often point
out an unusual area of rocks just off Broken
Arrow Peak between the first two towers of
the
Cable Car. This rock formation is reddish in
color, rounded and sandy looking. Many people
often mistake them for sandstone, yet, they
too are
granite. They are reddish in color and shaped
this way because of the extreme heat associated
with lava flows from nearby volcanoes millions
of years ago. Walt Disney visited Squaw Valley
in 1960 to help orchestrate
the opening ceremonies of the 1960 Winter Olympic
Games and was so enchanted by these rocks
that he returned home and designed The Big
Thunder Mountain
Railroad Ride at Disneyland after this ridgeline
of red granite rocks.
**Special thanks to forest ecologist Bob Wright for his contributions.
