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Large lahars hundreds of metres wide and tens of metres deep can flow several tens of metres per second (22 mph or more), much too fast for people to outrun. [9] On steep slopes, lahar speeds can exceed 200 kilometres per hour (120 mph). [9] A lahar can cause catastrophic destruction along a potential path of more than 300 kilometres (190 mi). [10]
Detailed map of Mount Rainier's summit and northeast slope showing upper perimeter of Osceola collapse amphitheater (hachured line) The Osceola Mudflow, also known as the Osceola Lahar, was a debris flow and lahar in the U.S. state of Washington that descended from the summit and northeast slope of Mount Rainier, a volcano in the Cascade Range during a period of eruptions about 5,600 years ago.
A lahar is a debris flow related in some way to volcanic activity, either directly as a result of an eruption, or indirectly by the collapse of loose material on the flanks of a volcano. A variety of phenomena may trigger a lahar, including melting of glacial ice, sector collapse , intense rainfall on loose pyroclastic material, or the outburst ...
A wide variety of volcanic processes can produce tsunamis. This includes volcanic earthquakes, caldera collapse, explosive submarine eruptions, the effects of pyroclastic flows and lahars on water, base surges with accompanying shock waves, lava avalanching into the sea, air waves from explosive subaerial eruptions, avalanches of cold rock, and avalanches of hot material. [1]
Fresh lahar channels are visible on Ruapehu's eastern slopes, 27 March 2007. The Eastern Ruapehu Lahar Alarm and Warning System (ERLAWS) is a lahar warning system that was installed on Mount Ruapehu, New Zealand following volcanic eruptions in 1995–1996. The system successfully detected and warned of an imminent lahar in March 2007.
Lahar deposits can take many months to dry out, until they can be walked on. The hazards derived from lahar activity can exist several years after a large explosive eruption. A team of US scientists developed a method of predicting lahars. Their method was developed by analyzing rocks on Mount Rainier in Washington. The warning system depends ...
The Mount Rainier Volcano Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. The AFM system was developed by the United States Geological Survey (USGS) in 1998 and is now maintained by Pierce County Emergency Management.
Tephra is a generalized word for the various bits of debris launched out of a volcano during an eruption, regardless of their size. [4] Pyroclastic materials are generally categorized according to size: dust measures at <1/8 mm, ash is 1/8–2 mm, cinders are 2–64 mm, and bombs and blocks are both >64 mm. [5] Different hazards are associated with the different kinds of pyroclastic materials.