Lahar

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Lahar

A lahar is a type of mudflow

Mudflow

A mudflow or mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose earth and water....
or landslide

Landslide

File:Guatemala landslide.jpgA landslide is a List of geological phenomena which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments....
composed of pyroclastic material and water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
that flows down from a volcano

Volcano

A volcano is an opening, or rupture, in a planet's surface or Crust , which allows hot, molten rock, ash, and gases to escape from below the surface....
, typically along a river

River

A river is a natural stream of water, usually freshwater, flowing toward an ocean, a lake, or another stream. In some cases a river flows into the ground or dries up completely before reaching another body of water....
valley

Valley

In geology, a valley is a Depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge....
. The term 'lahar" originated in the Javanese language

Javanese language

Javanese is the language of the people in the central and eastern parts of the island of Java, in Indonesia. In addition, there are also some pockets of Javanese speakers in the northern coast of western Java....
of Indonesia

Indonesia

The Republic of Indonesia , is a transcontinental country in Southeast Asia and Oceania. Comprising Islands of Indonesia, it is the world's largest Archipelago state....
. In Hindi

Hindi

Standard Hindi, also known as High Hindi, Nagari Hindi or Literary Hindi is a Standard language register of Hindi. It is one of the 22 official languages of India, and is used, along with English language, for administration of the central government....
'lahar' means 'wave'.

Lahars have the consistency of concrete

Concrete

Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, construction aggregate , water , and Chemistry admixtures....
: fluid when moving, then solid when stopped.

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Encyclopedia

Msh82 Lahar From March 82 Eruption 03 21 82

A lahar is a type of mudflow

Mudflow

A mudflow or mudslide is the most rapid and fluid type of downhill mass wasting. It is a rapid movement of a large mass of mud formed from loose earth and water....
or landslide

Landslide

Water

Volcano

A volcano is an opening, or rupture, in a planet's surface or Crust , which allows hot, molten rock, ash, and gases to escape from below the surface....
, typically along a river

River

Valley

In geology, a valley is a Depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge....
. The term 'lahar" originated in the Javanese language

Javanese language

Indonesia

The Republic of Indonesia , is a transcontinental country in Southeast Asia and Oceania. Comprising Islands of Indonesia, it is the world's largest Archipelago state....
. In Hindi

Hindi

Concrete

Mount Rainier

Mount Rainier is an activestratovolcano in Pierce County, Washington, located southeast of Seattle, Washington, Washington, in the United States....
in Washington

Washington

Washington is a U.S. state in the Pacific Northwest region of the United States. Washington was carved out of the western part of Washington Territory which had been ceded by Britain in 1846 by the Oregon Treaty as settlement of the Oregon Boundary Dispute....
produced a wall of mud deep in the White River

White River (Washington)

The White River is a river in the U.S. state of Washington. It flows about 75 miles from its source, the Emmons Glacier on Mount Rainier, to join the Puyallup River at Sumner, Washington....
canyon and extends over an area of over for a total volume of 2.3 cubic kilometers (0.55 cubic miles).

Lahars are very dangerous, because of their energy and speed. Large lahars can flow several dozen meters per second and can flow for many kilometres, causing catastrophic destruction in their path. The lahars from the Nevado del Ruiz

Nevado del Ruiz

Colombia

Colombia , officially the Republic of Colombia , is a country in north-western South America. Colombia is bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the north west by Panama; and to the west by the Pacific Ocean....
in 1985 caused the Armero tragedy, which killed an estimated 23,000 when the city of Armero

Armero

The Armero Tragedy was the aftermath of the November 13, 1985 Nevado del Ruiz eruption in Tolima Department, Colombia. The eruption of lava melted the mountain's large ice cap and produced floods, mudslides and a series of lahars that ultimately covered the Armero and killed most of its population, over 20,000 people out of 29,000 inhabit...
was buried under of mud and debris. New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous Islands of New Zealand, most notably Stewart Island/Rakiura and the Chatham Islands....
's Tangiwai disaster

Tangiwai disaster

The Tangiwai disaster on 24 December 1953 was the worst rail transport accident in New Zealand. An 11 carriage overnight express from Wellington to Auckland fell into the Whangaehu River at Tangiwai, ten kilometres north of Waiouru....
in 1953, where 151 people died after a Christmas Eve express train fell into the Whangaehu River

Whangaehu River

The Whangaehu River is a large river in central North Island of New Zealand. Its headwaters are the crater lake of Mount Ruapehu on the North Island Volcanic Plateau, and it flows into the Tasman Sea eight kilometres southeast of Wanganui....
, was caused by a lahar.

Lahars have several possible causes:

Snow
Snow

Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. The process of this precipitation is called snowfall....
and glacier
Glacier

A glacier is a large, slow-moving mass of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity and high pressure....
s can be melted by a pyroclastic flow
Pyroclastic flow

A pyroclastic flow is a common and devastating result of some volcano. The flows are fast-moving currents of hot gas and rock , which travel away from the volcano at speeds generally as great as 450 mi/h ....
during an eruption
A flood
Flood

A flood is an overflow of an expanse of water that submerges land, a deluge. In the sense of "flowing water", the word may also be applied to the inflow of the tide....
caused by a glacier, lake breakout
Lake breakout

Lake breakout is a geological term that refers to the collapse of a lake. High-altitude lakes tend to form in volcanic craters – where they are called crater lakes – or in valleys dammed as the result of earthquakes or glacier or volcanic deposition....
, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup
Jökulhlaup

A j?kulhlaup is a subglacial outburst flood. It is an Icelandic language term that has been adapted into the English language. It originally referred to the well-known subglacial outburst floods from Vatnaj?kull, which are triggered by a volcanic subglacial eruption, but now is accepted to describe any abrupt and large release of water from...
.

In particular, although lahars are typically associated with the effects of volcanic activity, lahars can occur even without any current volcanic activity, as long as the conditions are right to cause the collapse and movement of mud originating from existing volcanic ash deposits.

Several mountains in the world, including Mount Rainier

Mount Rainier

Mount Rainier is an activestratovolcano in Pierce County, Washington, located southeast of Seattle, Washington, Washington, in the United States....
in the USA, Mount Ruapehu

Mount Ruapehu

Mount Ruapehu, or just Ruapehu, is an active stratovolcano at the southern end of the Taupo Volcanic Zone in New Zealand. It is 23 kilometres northeast of Ohakune and 40 kilometres southwest of the southern shore of Lake Taupo, within Tongariro National Park....
in New Zealand

New Zealand

Galunggung

Galunggung , Galoen-gong, or Gunung Galunggung is an active stratovolcano in West Java, Indonesia.Hazardous eruption of 1982...
in Indonesia

Indonesia

The Republic of Indonesia , is a transcontinental country in Southeast Asia and Oceania. Comprising Islands of Indonesia, it is the world's largest Archipelago state....
, are considered particularly dangerous due to the risk of lahars. Several towns in the Puyallup River

Puyallup River

The Puyallup River is a river in the U.S. state of Washington. About long , it is formed by glaciers on the west side of Mount Rainier. It flows generally northwest, emptying into Commencement Bay, part of Puget Sound....
valley in Washington state, including Orting

Orting, Washington

Orting is a city in Pierce County, Washington, Washington, United States. The population is 6,075, according to the City of Orting....
, the closest to Mount Rainier, are built on top of lahar deposits that are only about 500 years old. Lahars are predicted to flow through the valley every 500-1,000 years, so Orting, Sumner

Sumner, Washington

Sumner is a city in northern Pierce County, Washington, Washington, United States. The population was 8,504 at the 2000 United States Census....
, Puyallup

Puyallup, Washington

Puyallup, Washington is a city in Pierce County, Washington, Washington about five miles east of Tacoma. The population was 33,011 at the 2000 United States Census....
, Fife

Fife, Washington

Fife is a city in Pierce County, Washington, Washington, United States. The population was 4,784 at the 2000 United States Census.History...
, and the Port of Tacoma

Tacoma, Washington

Tacoma is a mid-sized urban port city in and the county seat of Pierce County, Washington, United States. The city is on Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, Washington, and northwest of Mount Rainier National Park....
face considerable risk. The USGS has set up lahar warning sirens in Pierce County

Pierce County, Washington

Pierce County is the second most populous county in the U.S. state of Washington. Formed out of Thurston County, Washington on December 22, 1852, by the legislature of Oregon Territory...
, so that people can flee an approaching debris flow.

A lahar warning system has been set up at Mount Ruapehu by the New Zealand Department of Conservation

New Zealand Department of Conservation

The Department of Conservation , commonly known by its acronym, "DOC", is the state sector organisations in New Zealand of New Zealand which deals with the Conservation ethic of New Zealand?s natural and historic Cultural heritage....
and hailed a success after it successfully alerted officials to an impending lahar on 18 March 2007.

The 1991 Mount Pinatubo

Mount Pinatubo

Mount Pinatubo is an active stratovolcano located on the island of Luzon, at the intersection of the borders of the Philippine provinces of Zambales, Tarlac, and Pampanga....
eruption caused lahar as well, but it was due to the passing of a major typhoon over the Philippines

Philippines

The Philippines, officially known as the Republic of the Philippines, is a country in Southeast Asia with Manila as its capital city. It comprises 7,107 islands in the western Pacific Ocean....
which resulted in a torrent of volcanic ash

Volcanic ash

Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcano eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruptions...
and water

Water

Volcano

A volcano is an opening, or rupture, in a planet's surface or Crust , which allows hot, molten rock, ash, and gases to escape from below the surface....
. The lahar was caused by the mixing of settled ash and water from the monsoon which occurred the day after the volcano finished erupting. Although the eruption only killed 6 people, 1500 were killed in the resulting lahar, showing the destructive nature of lahars. In 1985, the volcano Nevado del Ruiz

Nevado del Ruiz

Nevado del Ruiz, also known as Mount Ruiz or Kumanday, is an Andes stratovolcano in the Caldas Department of Colombia. It is the northernmost volcano of the Andean Volcanic Belt, lying about west of Bogot?....
erupted, releasing large lahars. These lahar flows reached the town of Armero two hours after the eruption, burying the town and killing 3/4 of the townspeople, an estimated 23,000 people.

Lahar

See also

External links