Erupting volcanoes are among the most destructive forces in Mother Nature's arsenal. But where many people live on or near the flanks of such mountains, the real disaster often doesn't start until the eruption has subsided and the world has stopped paying attention.
It is then that rain-swollen rivers emanating from volcanic peaks can send massive lahars large waves of mud made up of water, ash and volcanic rock careening down the mountainsides, often burying everything in their paths, even entire towns and villages. Such lahars can occur for years after an eruption, depending on how much debris the volcano deposits and how much rain falls, until the sediment has either been cleaned off the mountain or has stabilized so that it doesn't erode easily.
Mount Pinatubo, northwest of Manila on the Philippine island of Luzon, erupted with devastating force in June 1991 and now is proving to be an ideal laboratory for studying the "hydrologic aftermath" of a volcanic eruption, said Karen Gran, a University of Washington doctoral student in Earth and space sciences.
Gran has been studying data compiled from 1997 through 2003 from five rivers on Pinatubo's flanks. The streams are in various stages of recovery, with one almost back to its pre-eruption state because it didn't become as clogged by sediment. But others traverse areas that still have vast amounts of sediment that can be washed away easily. Pinatubo's location, in the tropics not far north of the equator, makes it subject to torrential rains from monsoons and typhoons.
"In one of the streams we're studying, nothing can live. If a big storm hits, the whole riverbed moves," Gran said. That means that more than 13 years after the eruption, some of the rivers studied have not recovered to the point of having stable channels, which are necessary for a return of aquatic species and a general ecological recovery.
Gran is a lead author of a paper detailing the research on how streams on volcanoPage: 1 2 3 Related biology news :1
Contact: Vince Stricherz
University of Washington
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