Geology Cafe

Inland Basins: Lakes and Playas

Tectonic movements and volcanic eruptions can deflect streams, and create downwarps that become inland sedimentary basins. During extended dry periods these become interior drained basins. During wet periods they can fill with water, even spill over and flood into adjacent drainage basins. This has happened in California during the Ice Ages when great lakes filled places like Owen Valley, Panamint Valley, Death Valley, and much of the Great Basin region. glaciers california
Click on thumbnail images for a larger view.
Lake Tahoe is a high, inland, intermountain basin with a great clear freshwater lake. During the peak of the ice ages, great lake, much larger than Lake Tahoe filled the low regions of the Great Basin throughout the Nevada and northern Utah region, and large lakes filled the desert valley in California.
Mono Lake is a saline lake along the east side of the Sierra Nevada near Yosemite. The current lake is a remnant of a much greater lake that filled the basin during wet periods in the past. Today the lake support brine shrimp that can tolerate high concentrations of sodium bicarbonate in the lake water.
"Tufa towers"are deposits of calcium carbonate deposit that formed around spring vents upwelling beneath Mono Lake when water levels were higher.
Trona Towers are large tufa spring deposits that formed in the ancient China Lake basin area near Death Valley National Park. Trona is a mining town associated with mining of salts and sedimentary minerals that accumulated in the ancient lake basin.
Death Valley is a great playa-filled basin in the Mojave Desert. Minerals dissolved from the mountain regions precipitate as salts and clay minerals where stream terminate in the basin. Shoreline Butte is a low mountain in southern Death Valley where old shoreline benches are preserved form when Lake Manly flooded the valley. Today, much of lower Death Valley is below -200 feet below sealevel. During wet periods of the Ice Ages, ancient Lake Manly was as much as 800 feet deep.
During wet periods, shallow, ephemeral lakes fill low areas within the basins. During dry periods, they dry out. During dry periods, wind action dominates, and old lakebed deposits are transported into dunes. These dunes are near Stovepipe Springs in Death Valley. Soda Lake is a broad, shallow interior-drained basin in Carrizo Plain National Monument. The basin is located in the valley of the San Andreas Fault Zone in central California. The playa (lake bed) floods episodically in wet periods, and becomes a muddy plain covered with sodium carbonate salt beds during drought periods.
Soda Lake is also the name of the great lake bed of ancient Lake Mannix in the Mojave Desert. This small freshwater spring is one of the few locations for water for wildlife in a large region. Salt-covered mudflats are in the distance Saratoga Spring is a very rare large spring in the southern end of Death Valley. The spring is rich in salt content, but supports a variety of wildlife including rare pupfish that are living descendents of fish that lived in the Great Basin lakes during the Ice Ages.
Devils Golf Course is a large salt pan in Death Valley in the bed of was once ancient Lake Manly. As the salt dries out and crystallizes, it pushes up pieces of muddy salty crust into sharp edges. The Panamint Mountains (over 11,000 feet) are in the distance. A salt stream flows into the lower basin area of Death Valley. This view shows "salt polygons"forming as salts precipitate along the stream channel.