by Kimberly Bunch

Created on: April 29, 2009   Last Updated: May 04, 2009

Lahars are a form of mudslide or landslide that doesn't necessary need to be triggered by volcanism. The name lahar derives from the Javanese Hindi language in Indonesia. The volcanic mud-flow in Hindi means wave. Lahars can effect all of the mountains of the world; but not all of them are prone to lahars. The appearance of lahars from the pyroclastic result create a cone shape top that covers the top of the crater that are often snow covered or contains water in a crater lake.

Lahars can result from volcanic eruption or by melting glaciers that produce flooding in the summit crater, or by heavy rainfall, or ice in the crater. In addition, water deposits that produce lahars can occur at (or) beneath the crater of the mountain. Thereby, producing glacial outburst (s) from the flooding activity, or by a volcano eruption. The eruption of pyroclastic density can flow out tens of meters per second and spread several kilometers away.

Lahars are superheated to temperatures that can range up to 1250 degrees. The shape and size it takes on varies. It depends on the clay deposit ingredients of the consistency. Lahar can build up its consistency of hot gas, ash, and rock to 10 meters, or more. The flowing material of pyroclastic resembles a bed of hot liquid concrete rushing by. Their speed and makeup depends on the texture and consistency of the clay content. They can either be cohesive or non-cohesive. The cohesive lahar picks up debris in is way and can reach heights of 100 meters or more.

They can range from ten to hundreds of kilometers downstream and take out anything in its way depending on the clay content. Cohesive texture contains more than 3 to 5 percent clay which allows the flow to stay at its consistency as it rushes down the mountain into the lower lying valley entering into nearby streams and rivers. If the sediment content reaches 60 percent it can be a very violent construction of deadly moving force that will take out any bridges, building, and anything else that is in its path. Lahars can travel up to 100 miles an hour and take anything in its path down if it is cohesive.

If the flow is non-cohesive it contains 1 to 5 percent clay and is diluted as it flows with little consistency that outruns the sediment. This type will lose speed as it sheds sediment; making its flow slow down and continue to decrease in size and shape. The mountains that are known for producing lahars are high threat areas such as: USA at Mount Rainier, New Zealand's Mount Ruapehu,

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