Lake Bonneville

Lake Bonneville

Overview
Lake Bonneville was a prehistoric pluvial lake
Pluvial lake
A pluvial lake is a landlocked basin which fills with rainwater during times of glaciation, when precipitation is higher. Pluvial lakes that have since evaporated and dried out may also be referred to as paleolakes.-Geology:...

 that covered much of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

's Great Basin
Great Basin
The Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...

 region. Most of the territory it covered was in present-day Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, though parts of the lake extended into present-day Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

 and Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

. Formed about 32,000 years ago, it existed until about 14,500 years ago, when a large portion of the lake was released through the Red Rock Pass
Red Rock Pass
Red Rock Pass is a low mountain pass in eastern Idaho, south of Downey in southern Bannock County. It is geologically significant as the spillway of ancient Lake Bonneville...

 in Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

. Following the Bonneville Flood
Bonneville Flood
The Bonneville Flood or Lake Bonneville Flood was a catastrophic flooding event in the previous ice age, which involved massive amounts of water inundating parts of southern Idaho and eastern Washington along the course of the Snake River. Unlike the Missoula Floods, which also occurred during the...

, as the release is now known, the lake receded to a level called the Provo Level.
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Encyclopedia
Lake Bonneville was a prehistoric pluvial lake
Pluvial lake
A pluvial lake is a landlocked basin which fills with rainwater during times of glaciation, when precipitation is higher. Pluvial lakes that have since evaporated and dried out may also be referred to as paleolakes.-Geology:...

 that covered much of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

's Great Basin
Great Basin
The Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...

 region. Most of the territory it covered was in present-day Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, though parts of the lake extended into present-day Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

 and Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

. Formed about 32,000 years ago, it existed until about 14,500 years ago, when a large portion of the lake was released through the Red Rock Pass
Red Rock Pass
Red Rock Pass is a low mountain pass in eastern Idaho, south of Downey in southern Bannock County. It is geologically significant as the spillway of ancient Lake Bonneville...

 in Idaho
Idaho
Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state....

. Following the Bonneville Flood
Bonneville Flood
The Bonneville Flood or Lake Bonneville Flood was a catastrophic flooding event in the previous ice age, which involved massive amounts of water inundating parts of southern Idaho and eastern Washington along the course of the Snake River. Unlike the Missoula Floods, which also occurred during the...

, as the release is now known, the lake receded to a level called the Provo Level. Many of the unique geological characteristics of the Great Basin are due to the effects of the lake.

At more than 1,000 feet (305 m) deep and more than 19691 square miles (50,999.5 km²) in area
Area
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

, the lake was nearly as large as Lake Michigan
Lake Michigan
Lake Michigan is one of the five Great Lakes of North America and the only one located entirely within the United States. It is the second largest of the Great Lakes by volume and the third largest by surface area, after Lake Superior and Lake Huron...

 and significantly deeper. With the change in climate, the lake began drying up, leaving Great Salt Lake
Great Salt Lake
The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the western hemisphere, the fourth-largest terminal lake in the world. In an average year the lake covers an area of around , but the lake's size fluctuates substantially due to its...

, Utah Lake
Utah Lake
Utah Lake is a freshwater lake in the U.S. state of Utah. On the western side of Utah Valley, the lake is overlooked by Mount Timpanogos and Mount Nebo. The lake's only river outlet, the Jordan River, is a tributary of the Great Salt Lake and is highly regulated with pumps. Evaporation accounts...

, Sevier Lake
Sevier Lake
Sevier Lake is an intermittent and endorheic lake which lies in the lowest part of the Sevier Desert, Millard County, Utah. Like Great Salt Lake and Utah Lake, it is a remnant of Pleistocene Lake Bonneville. Sevier Lake is fed primarily by the Beaver and Sevier rivers, and the additional inflow...

, Rush Lake
Rush Lake (Utah)
Rush Lake is a shallow saline lake in Tooele County in the U.S. state of Utah. It is a 16,800 year old remnant of Lake Bonneville, an ancient lake that formed approximately 32,000 years ago...

, and Little Salt Lake as remnants.

Lake Bonneville was named by the geologist G. K. Gilbert
Grove Karl Gilbert
Grove Karl Gilbert , known by the abbreviated name G. K. Gilbert in academic literature, was an American geologist....

 after Benjamin Louis Eulalie de Bonneville
Benjamin Bonneville
Benjamin Louis Eulalie de Bonneville was a French-born officer in the United States Army, fur trapper, and explorer in the American West...

 (1796–1878), a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

-born officer in the United States Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

, who was also a fur trapper
Fur trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of world market for in the early modern period furs of boreal, polar and cold temperate mammalian animals have been the most valued...

, and explorer in the American West. Bonneville was noted for his expeditions to the Oregon Country
Oregon Country
The Oregon Country was a predominantly American term referring to a disputed ownership region of the Pacific Northwest of North America. The region was occupied by British and French Canadian fur traders from before 1810, and American settlers from the mid-1830s, with its coastal areas north from...

 and the Great Basin.

Geologic history



Like most, if not all, of the ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 pluvial lakes of the American West
Western United States
.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

, Lake Bonneville was a result of the combination of lower temperatures, decreased evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

, and higher precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 that then prevailed in the region, perhaps because of a more southerly jet stream
Jet stream
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere and the stratosphere . The major jet streams on Earth are westerly winds...

 than today's. The lake was probably not a singular entity either; geologic evidence suggests that it may have evaporated and reformed as many as 28 times in the last 3 million years.

Great Salt Lake
Great Salt Lake
The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the western hemisphere, the fourth-largest terminal lake in the world. In an average year the lake covers an area of around , but the lake's size fluctuates substantially due to its...

, Utah Lake
Utah Lake
Utah Lake is a freshwater lake in the U.S. state of Utah. On the western side of Utah Valley, the lake is overlooked by Mount Timpanogos and Mount Nebo. The lake's only river outlet, the Jordan River, is a tributary of the Great Salt Lake and is highly regulated with pumps. Evaporation accounts...

, and Sevier Lake
Sevier Lake
Sevier Lake is an intermittent and endorheic lake which lies in the lowest part of the Sevier Desert, Millard County, Utah. Like Great Salt Lake and Utah Lake, it is a remnant of Pleistocene Lake Bonneville. Sevier Lake is fed primarily by the Beaver and Sevier rivers, and the additional inflow...

 are the largest remnants of the original Lake Bonneville. Several levels of the old shorelines are still visible above Salt Lake City, along the Wasatch Front
Wasatch Front
The Wasatch Front is a metropolitan region in the north-central part of the U.S. state of Utah. It consists of a chain of cities and towns stretched along the Wasatch Range from approximately Santaquin in the south to Brigham City in the north...

 and elsewhere. The appearance of the shorelines is that of a shelf or bench protruding from the mountainside, well above the valley floor. Four main shorelines are associated with the fluctuating levels of the ancient lake. The Stansbury, Bonneville, Provo and Gilbert shorelines each mark a time when lake level remained constant long enough to deposit massive accumulations of sand and gravel.

The Bonneville Bench, at approximately 1,555 m (~5,100 ft.) elevation, is part of the preserved ice age shoreline. This shoreline marks the highest level attained by the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 lake approximately 15,500 years ago. During this period, the lake covered over 52,000 km² (20,000 sq mi) and was over 300 m (1000 ft) deep in places.

About 14,500 years ago, the lake level fell catastrophically as Lake Bonneville overflowed
Bonneville Flood
The Bonneville Flood or Lake Bonneville Flood was a catastrophic flooding event in the previous ice age, which involved massive amounts of water inundating parts of southern Idaho and eastern Washington along the course of the Snake River. Unlike the Missoula Floods, which also occurred during the...

 near Red Rock Pass
Red Rock Pass
Red Rock Pass is a low mountain pass in eastern Idaho, south of Downey in southern Bannock County. It is geologically significant as the spillway of ancient Lake Bonneville...

, Idaho and washed away a natural dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 formed by opposing overlapping alluvial fan
Alluvial fan
An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...

s. The lake level fell some 105 m (350 ft.) to what is now the next lower bench (the "Provo level") in a flood that geologists estimate to have lasted up to a year. It is estimated that this breach released 1000 cubic miles (4,168.2 km³) of water in the first few weeks. The Provo level is the most easily recognized shoreline feature throughout the Bonneville basin and is distinguished by thick accumulations of tufa
Tufa
Tufa is a variety of limestone, formed by the precipitation of carbonate minerals from ambient temperature water bodies. Geothermally heated hot-springs sometimes produce similar carbonate deposits known as travertine...

 that formed near the shorelines during the 500 years that the lake was at this level.

About 14,000 years ago, the lake started to drop again because of changing climate conditions, and by 12,000 years ago, the lake reached a level even lower than that of the modern day Great Salt Lake. A slight transgression or rise in lake level occurred about 10,900 to 10,300 years ago and formed the Gilbert shoreline. The Gilbert shoreline is the least conspicuous of the major shorelines but evidence of it remains at Antelope Island
Antelope Island
Antelope Island, with an area of , is the largest island of 10 islands located within the Great Salt Lake, Utah, United States. The island lies in the southeastern portion of the lake, near Salt Lake City and Davis County, and becomes a peninsula when the lake is at extremely low levels. Antelope...

 and in large coastal features, such as the Fingerpoint Spit near the Hogup Mountains.

In addition to geological traces, the lake has left a legacy of related fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 distributed in now-isolated bodies of water. The term "Lake Bonneville drainage" is often used to refer to the assembly of disconnected lakes and rivers; since the draining happened relatively recently, most of the fish have not had time to evolve into distinct species.

See also

  • List of prehistoric lakes
  • Lake Lahontan
    Lake Lahontan
    Lake Lahontan was a large endorheic Pleistocene lake of modern northwestern Nevada that extended into northeastern California and southern Oregon...

  • Bonneville cutthroat trout
    Bonneville cutthroat trout
    The Bonneville cutthroat trout is a subspecies of cutthroat trout native to tributaries of the Great Salt Lake, U.S.A. Most of the fish's current and historic range is in Utah, but they are also found in Idaho, Wyoming, and Nevada...

    : endemic to area formerly covered by Lake Bonneville
  • Bonneville Salt Flats

External links