Causes
Lahars have several possible causes:
- Snow and glaciers can be melted by lava or pyroclastic flows during an eruption.
- Lava flow out of open vents can mix with wet soil, and mud on the slope of the volcano making a very viscous, high energy lahar.(The higher up the slope of the volcano the more gravitational potential energy the flow will have)
- A flood caused by a glacier, lake breakout, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup
- Water from a crater lake, combined with volcanic material in an eruption
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.
- Snow and glaciers can melt during periods of mild weather
- Earthquakes underneath or close to the volcano can shake material loose and cause it to collapse triggering a lahar avalanche.
- Rainfall or typhoons can cause the still-hanging slabs of solidified mud to come rushing down the slopes at a speed of more than 30 Kilometers per hour, causing devastating results.
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