Lake Tahoe: The Geology - Memorial Point Scenic Overlook
N 39° 12.576 W 119° 55.790
11S E 247028 N 4344127
A few interpretive displays describe the geology of Lake Tahoe at Memorial Point Scenic Overlook.
Waymark Code: WMTNDQ
Location: Nevada, United States
Date Posted: 12/17/2016
Views: 2
Located outside the Memorial Point Scenic Overlook Visitor Center are a number of interpretive displays. A few of them describe the geology of Lake Tahoe. One of the displays reads:
Lake Tahoe: The Geology
Millions of years of heat and pressure created the solid granite bedrock under this region of North America. Here at Lake Tahoe, the most recent 10 million years have shaped what you see today.
Active volcanoes, fault lines and glaciers chiseled the granite into boulders and surface outcrops. Water and wind erosion around the lake created and drifted the sand.
Double Fault
While it appears the lake may be the remnant of an ancient volcano (like Oregon's Crater Lake), Lake Tahoe basin was actually formed 5 to 10 million years ago when the valley sank away from two faults, lifting the surrounding mountains.
Fire and Ice
About 2 million years ago, lava flowing from Mt. Pluto dammed the outlet into the Truckee River, causing the lake to rise 600 feet above its current level.
Over the last million years, extended periods of extreme cold - known as the Ice Age - wide U-shaped valleys that now hold Emerald Bay and Cascade Lake.
Another nearby interpretive display adds more information on the geology of Lake Tahoe and reads:
Creating a Masterpiece
Lake Tahoe's history is one of fire and ice. Several million years of earth movements, volcanism, and glaciation have created this masterpiece.
Ten million years ago, the Sierra Nevada Mountains, pushed by forces below the earth's crust, began to rise. As pressures grew, the land split along faultlines, creating blocks of uplift interspersed with sinking basins -- the Tahoe Basin is one of these. The lake was formed around two million years ago, when tectonic uplift and volcanic mudflows blocked the Truckee River.
Ice Age glaciers continued to shape the lake. Huge ice dams repeatedly blocked its outflows, raising its level until the waters broke through the ice to flood the valleys below.
Ancient terraces show that the lake was, at times, up to 800 feet deeper than present-day levels. During this era, the lake was cloudy with glacial silt.
The last Ice Age waned around 20,000 years ago. Silt settled to the lake's bottom leaving the water extraordinarily clear. Plants colonized the slopes above, and sterile glacial sands slowly became rich soils. Forests sprouted and animals moved into the watershed.
Lake Tahoe, like all natural lakes, will continue to evolve over time. Although change is inevitable, the Tahoe we enjoy today represents an uncommon beauty unique in the world.
In addition to the wonderfully blue, crystal clear waters of Lake Tahoe, the sculpted granite boulders that line the shores of the lake are also an attractive feature that look like large pebbles.