Lake breakout is the collapse of a lake, usually of high-altitude. High-altitude lakes tend to form in

volcanic crater A volcanic crater is an approximately circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During volcanic eruptions, molten magma and volcanic gases rise from an und ...

s – where they are called

crater lake Crater Lake ( Klamath: ''Giiwas'') is a volcanic crater lake in south-central Oregon in the western United States. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fill ...

s – or in valleys dammed as the result of

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

s or

glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...

or volcanic deposition. Lake breakouts are most common a few weeks or months after a

volcanic eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are oft ...

as a river becomes blocked by volcanic debris.

Process

The walls of such lakes can be unstable and may be breached after fresh earthquakes or because of

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...

. As water rushes outwards, the initial channel is cut wider and deeper, further increasing the flow. This may cause the lake's rim to collapse abruptly. The usual result is for huge amounts of water to be displaced, incorporating a great deal of

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

which increases it in volume by as much as two or four times, or even more. This produces violent floods and

lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extr ...

s with devastating effects for any settlements in their path.

Historical events

The larger a temporary lake is, the more extreme the likely breakout will be. One of the largest known to have occurred in recent geological history was the collapse, around 15,000 years ago, of the ancient

Lake Bonneville Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...

which was filled with meltwater from the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

and covered large areas of

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

Idaho Idaho ( ) is a U.S. state, state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Monta ...

and

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

. Erosion broke through the lake shore's lowest point, the

Red Rock Pass Red Rock Pass is a low mountain pass in the western United States in southeastern Idaho, located in southern Bannock County, south of Downey. It is geologically significant as the spillway of ancient Lake Bonneville. It is traversed by U.S ...

in Idaho, releasing as much as 1,000 mile³ (4,000 km³) of water within a period estimated to have lasted only two weeks. The energies released by the outburst were capable not just of stripping surface features, but gouging out bedrock to a depth of many feet. It drastically reshaped the landscape downstream, carving out many of the features of the

Snake River The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snake ...

and its surrounding area.

Glacial Lake Missoula Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...

also had lake breakouts, due to breaking of ice dams, see

Missoula Floods The Missoula floods (also known as the Spokane floods or the Bretz floods or Bretz's floods) were cataclysmic glacial lake outburst floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the las ...

. These lake breakouts caused extensive erosion throughout eastern

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. It has been suggested that gigantic breakouts from underground lakes may have been responsible for carving some of the

canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to cu ...

s of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

Mitigation

Although there is little that can be done about many lake breakouts, some have been prevented (or at least delayed) by human intervention. The 1980 eruption of Mount St. Helens blocked nearby Castle Creek, forming a lake which geologists feared would produce a sudden lahar. The

United States Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...

excavated an outlet channel which prevented the lake from overtopping its new

debris dam A landslide dam or barrier lake is the natural damming of a river by some kind of landslide, such as a debris flow, rock avalanche or volcanic eruption. If the damming landslide is caused by an earthquake, it may also be called a quake lake. ...

. {{DEFAULTSORT:Lake Breakout Flood Volcanoes Seismology