Lake Manly

Lake Manly
File:Lake Manly system.png The Lake Manly system rendered as it appeared during its last maximum 22,000 years ago
Location	Death Valley Inyo County, California
Coordinates
Lake type	Endorheic rift lake (former)
Primary inflows	Furnace Creek Wash
Primary outflows	Terminal
Basin countries	United States
Max. length	130 km (81 mi)
Max. width	10 km (6.2 mi)
Surface area	260 km2 (100 sq mi)
Max. depth	180 m (590 ft)
Surface elevation	−85 m (−279 ft)
Sections/sub-basins	Badwater Basin Middle Basin Cotton Ball Marsh

Lake Manly was a pluvial, former freshwater, endorheic, rift lake that filled the Death Valley basin of Inyo County, California through the Holocene before the area's climate changed to desert. Following its isolation from the Colorado River system, Lake Manly receded by evaporation with Badwater Basin, Middle Basin, and Cotton Ball Marsh occupying the space left behind. At its greatest extent Lake Manly was roughly 80 mi (130 km) long and 600 ft (180 m) deep.

Background

Shoreline Butte showing strandlines from ancient Lake Manly.

Pleistocene Lakes and Rivers of Mojave

As Lake Manly evaporated to the surface of Death Valley, it left a remarkable legacy. Under the surface of Death Valley is one of the world's largest aquifers. Being fed by the Amargosa River and Salt Creek, this aquifer is barely visible above ground at Badwater Basin, at −279 ft (−85 m).

Shoreline Butte has easy-to-see strandlines formed by wave action from the ancient lake. These features were created by strands of the lake, which would change its depth over time and also cause slight changes in climate. The conditions under which this lake existed are called "pluvial" by geologists instead of glacial because glaciers did not directly touch Death Valley, but the meltwater from the glaciers and the cooler and wetter climate of the time affected the valley. Approximately 8,000 ft (2,400 m) of gravel, sand, and mud overlay the bedrock of the valley floor.

Lake Manly was named after William L. Manly, who was among the original Death Valley party in 1849. Manly and a companion hiked out of Death Valley into the Greater Los Angeles Area, where he found help and returned to rescue his party.

Geologic Timeline

In 1999, geologists drilled a 186-meter deep core into the Death Valley floor near Badwater Basin. The core has shed light on the contemporary understanding of Lake Manly's age and clearly divided Lake Manly's history into six distinct time periods. The six time periods all clearly corresponded to the climate in Death Valley, which was the driving force behind Lake Manly's formation and disappearance.

1. 192 to 186 ka—The climate was dry and the ground was dominated by saltpans or shallow ephemeral lakes.
2. 186 to 120 ka—The climate was relatively cold with abundant inflow, the first primary manifestation of Lake Manly and the time during which it reached its maximum.
3. 120 to 60 ka—The climate was a dry period when mudflats stretched across the valley bottom.
4. 60 to 35 ka—The climate was cool, but relatively arid and without enough inflow to sustain anything but very shallow saline lakes.
5. 35 to 10 ka—The climate was cold and wet, allowing for consistent inflow that fed a perennial saline lake, the second primary manifestation of Lake Manly.
6. 10 ka to the present—The climate is dry and warm, so the minor inflow quickly evaporates, forming mudflats and salt flats.

Depositional Features

Lake Manly left behind many deposits, indicating the range of its waters. Geologists have discovered 30 distinct deposits. The deposits range from strandlines to shoreline gravel to spit and bar complexes, among others. The numerous features span Death Valley from north to south, but are primarily located on the eastern side. Despite how far ranging the features are, the record of deposition is far more incomplete than other Pleistocene pluvial lakes such as Lake Bonneville or Lake Lahontan. Deposits from Lake Manly are often only partially intact because they have been affected by erosion or faulting. The depositional features provide insight into Lake Manly's history and expand the geologic understanding of the region.

Reemergence

In 2004, severe flooding resulted in Lake Manly reappearing on a large scale. More than 100 square miles (260 km²) were covered by the lake, allowing some tourists and park rangers to become probably the only humans to canoe across Death Valley. The lake was about two feet deep at its deepest point. It evaporated quickly, leaving behind a mud-salt mixture.

A series of unusual storms in October 2015 caused large amounts of damage throughout Death Valley National Park. Flash floods destroyed significant portions of multiple roads and heavily damaged several historic structures at Scotty's Castle and deposited debris in Devils Hole.

See also

• List of lakes in California
• Pluvial lake

External links

• Death Valley geology field trip - Shoreline Butte USGS
• 3-D Geology of Death Valley National Park USGS
• Geology USGS
• Lake Manly at mcgill.ca