The Geology and History of Mono Lake
You can also learn more about kayaking and canoeing on Mono Lake.
Geologic History of Mono Lake
Mono Lake Basin was formed by the same geologic processes that shaped the Nevada and Eastern Sierra landscape over the past several million years. Extension, or pulling apart, of the Earth’s crust has created north/south trending mountain ranges flanked by deep, long valleys. Later volcanism (around 2.5 million years ago) poured thick accumulations of molten rock (basalt) into the valleys, shaping the landscape and creating natural dams that controlled the flow of water.
The basin began filling with water around ¾ of a million (750,000) years ago, or around the time that the Long Valley Caldera violently erupted to the southeast of the lake. Water sourced from melting ice sheets located on the eastern flank of the Sierra Nevada Mountains flowed downslope and was captured by the basin. During this time in the Earth’s history, the region’s climate was cooler and wetter, limiting evaporation from the lake and providing abundant precipitation. These climatic conditions likely persisted until the end of the latest ice age (around 11,000 years ago), when Mono Lake reached it’s greatest depth of 900 ft. At the termination of this ice age, the climate naturally shifted to drier, warmer conditions and the alpine ice sheets became extinct, cutting off a major supply of fresh water to the basin.
Mono Lake is what geologists refer to as an endorheic basin, meaning that water flows into the lake, but the lake has no outflow. With no outflow, salts accumulate in the lake as water evaporates, making the water body hypersaline (more salty than the ocean) and creating a very unique ecosystem.
Volcanic activity has been ongoing in the Mono Lake Basin for at least the past 2.5 to 3 million years. The most recent volcanic eruptions, which occurred only 400 years ago, are related to the conical cinder cones of Mono Craters to the south of the lake (flanking U.S Route 395). These ‘modern’ eruptions formed the Paoha Island in the center of the lake, which is now an important breeding ground for a variety of song and sea birds.
Along the southern shoreline of Mono Lake, large tufa towers or pinnacles rise above the water’s surface. These iconic pillars, comprised of precipitated calcium carbonate, formed over thousands of years by the interaction of freshwater springs and the highly alkaline waters of Mono Lake. Today, several of the large tufa towers are now nesting sites for predatory Osprey and bird watching is strongly encouraged.
A small band of the Northern Paiute Tribe known as the Kucadikadi, or pupae eaters, were some of the first humans to inhabit the Mono Lake region. These indigenous people were primarily supported by the lake, obtaining a substantial amount of their nutrition from the larvae of the alkali flies that live in and around the muddy shorelines. The Kucadikadi were exceptional basket weavers and by the 20th century, many of the remaining tribe members relied on the tourist trade for existence.
Monoville: Digging up the past
In 1859, migrant prospectors discovered placer gold along the northwest shores of Mono Lake and the town Monoville instantly sprung up, quickly reaching a population of 1200 residents a year later. Although devoid of the hefty nuggets that made the western Sierra slope so popular, the Mono Lake mining district contained large amounts of what the miner’s termed “shot gold”, which are flat flakes about the size of rice. This made recovery difficult for individual miners and by the early 1860’s, most of the mineral claims were consolidated by large hydraulic mining companies.
In an attempt to economically recover the fine gold flakes from the hills flanking the lake, a 12 to 14 mile long ditch and sluice network was constructed in the early 1860’s to provide water for mining. Water from Virginia Creek was transported to the arid Monoville area for large-scale hydraulic mining. This labor intensive and costly undertaking did not pan out for the miners of Monoville and by the middle of the 1860’s, almost all of the residents had emigrated from the area to more promising mining towns.
The Monoville workings were the first major gold discoveries in the Eastern Sierra region and the excitement caused a rapid influx of businessmen and miners to the Mono Lake Basin. Twenty years after the discovery at Monoville, prospectors struck gold at nearby Bodie and the region again experienced a period of rapid population growth as the mines began producing precious metals.
Although very little remains of the Monoville town site today, visitors can still get a grasp on the harsh conditions 19th-century miners endured when extracting natural resources in the west. None of the town’s buildings are still standing, although remnants of the water ditch and the scars of hydraulic mining are still apparent throughout Rattlesnake Canyon. To get to the site, head east for a short distance on the maintained Conway Ranch dirt road, which is located about one mile north of the junction of U.S. Route 395 and State Route 167 (4.5 miles north of Lee Vining, CA). A California State Historic Marker indicates the location of the town site and summer visitors are reminded to be aware of the reptiles that inspired the canyon’s name.
Preservation of Mono Lake
In the early 1940’s, Eastern Sierra runoff water that would have naturally fed Mono Lake was diverted into the Los Angeles Aqueduct system. Without adequate inflow and recharge from the runoff, evaporation quickly caused lake levels to drop and water salinity levels to increase. By 1990, the lake had lost over half of its water volume and salinity levels doubled, creating an ecological disaster and health hazard (due to airborne alkaline dust) for the region.
In 1994, the California State Water Resources Control Board issued orders to protect the Mono Lake Basin in response to outcries by several conservation groups. Although the lake will likely never fully recover to its pre-diversion levels, lake levels have steadily risen and target lake levels may be reached by the end of the decade. On the positive side, the lowering of the lake exposed the spectacular and photogenic tufa towers that characterize the lake and mesmerize visitors today.
The natural beauty of this desert water body is as diverse as its history. For additional information about the geologic, natural, and early anthropogenic history of the region, visit the Mono Basin National Forest Scenic Area Visitor Center. This facility, located just off of US Route 395 north of Lee Vining, CA., has extensive exhibits informing visitors about the natural and human-influenced history of the lake and seasonal guided group tours of the area are also available.