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Scientists Monitor Freak Mudflowhttp://www.livescience.com/environment/070713_kiwi_mudflow.htmlScientists Monitor Freak Mudflow By Andrea Thompson, LiveScience Staff Writer \ A mudflow that recently burst through the banks of a volcanic lake in New Zealand gave scientists an up-close and personal view of the freak event and a chance to test their disaster warning systems. The mudflow was of a type called a lahar, in which water and sediments flow down from a volcano either when snow and glaciers rapidly melt during a volcanic eruption or when the water in a volcanic crater lake breaks through its banks. In this case, Crater Lake, atop Mount Ruapehu on New Zealand’s North Island, was predicted to overtop its banks in 2007 but had recently stopped filling as rapidly, and the forecast was pushed back to 2008. But several days of intense rainfall caused the lake’s banks to collapse much sooner, on March 18, 2007, releasing about 1.3 million cubic meters of water. Visiting scientists were on hand before and after the event to observe it. “We found a broad area covered in a veneer of mud and boulders,” said volcanologist Sarah Fagents of the University of Hawaii at Manoa. “It was an unprecedented opportunity to see the immediate aftermath of such an event.” A lahar warning system installed on Ruapehu successfully alerted officials to the onset of the lahar. Prediction of lahars is particularly important in populated volcanic regions such as Washington state and Indonesia. “Lahars can be extremely hazardous, especially in populated areas, because of their great speed and mass,” said William Leeman, a program director for the National Science Foundation, which funded the work. “They can flow for many tens of miles, causing catastrophic destruction along their path.” “The 1980 eruptions at Mount St. Helens, for example, resulted in spectacular lahar flows that choked virtually all drainages on the volcano, and impacted major rivers as far away as Portland, Oregon,” he added. No major damage was done by the Ruapehu lahar as officials closed off roadways and shut down train lines, and the mudflow failed to overtop the river channel it rushed down. By Andrea Thompson, LiveScience Staff Writer \ A mudflow that recently burst through the banks of a volcanic lake in New Zealand gave scientists an up-close and personal view of the freak event and a chance to test their disaster warning systems. The mudflow was of a type called a lahar, in which water and sediments flow down from a volcano either when snow and glaciers rapidly melt during a volcanic eruption or when the water in a volcanic crater lake breaks through its banks. In this case, Crater Lake, atop Mount Ruapehu on New Zealand’s North Island, was predicted to overtop its banks in 2007 but had recently stopped filling as rapidly, and the forecast was pushed back to 2008. But several days of intense rainfall caused the lake’s banks to collapse much sooner, on March 18, 2007, releasing about 1.3 million cubic meters of water. Visiting scientists were on hand before and after the event to observe it. “We found a broad area covered in a veneer of mud and boulders,” said volcanologist Sarah Fagents of the University of Hawaii at Manoa. “It was an unprecedented opportunity to see the immediate aftermath of such an event.” A lahar warning system installed on Ruapehu successfully alerted officials to the onset of the lahar. Prediction of lahars is particularly important in populated volcanic regions such as Washington state and Indonesia. “Lahars can be extremely hazardous, especially in populated areas, because of their great speed and mass,” said William Leeman, a program director for the National Science Foundation, which funded the work. “They can flow for many tens of miles, causing catastrophic destruction along their path.” “The 1980 eruptions at Mount St. Helens, for example, resulted in spectacular lahar flows that choked virtually all drainages on the volcano, and impacted major rivers as far away as Portland, Oregon,” he added. No major damage was done by the Ruapehu lahar as officials closed off roadways and shut down train lines, and the mudflow failed to overtop the river channel it rushed down. |
| The Inquisitor |
http://www.livescience.com/environment/070318_ap_nz_volcano.html
Mud, Rocks Rush From New Zealand Volcano And this was just four months ago. WELLINGTON, New Zealand (AP) — A mix of mud, acidic water and rocks tore down the slope of a volcano in New Zealand on Sunday, bursting through a 23-foot wall of volcanic ash and sand built up in an eruption 12 years ago. The mud flow — also known as a lahar — broke through the rubble wall atop Mount Ruapehu's crater lake Sunday morning, triggering an early warning alarm, local authorities said. Police and civil defense workers immediately closed roads and the nation's main trunk rail near the southern base of the mountain on New Zealand's North Island. The island's main north-south highway, some 30 miles from the mountain's base, also was closed and two passenger trains with 200 people on board were halted some distance from the mountain. A lahar that tore down the same volcano in 1953 killed 151 people when it washed away a rail bridge, plunging a passenger train into the raging torrent of liquid mud. On Sunday, millions of gallons of acidic water breached the naturally occurring wall of volcanic ash and sand known as tephra, regional council chairman Gary Murfitt said. More than 130 feet of the tephra's wall was washed away — a dozen years after it had built up in Ruapehu's 1995 eruption, said Dr. Harry Keys, a lahar expert with the Conservation Department. Farmer Josh Wallace said the lahar carried rocks, mud and trees down the Whangaehu River that runs through his property. ŇThe water was a concrete color ... it was so gray. You could feel the rocks in the water hitting the bank,'' he told National Radio. There were no immediate reports of damage, apart from flooding on some farmland near the base of the mountain. There was also no threat to human life. Scientists had been able to predict the lahar's passage and the early warning system had worked as planned, Conservation Minister Chris Carter said. In the 1953 lahar, the bodies of some of the dead were washed high into trees as the torrent spewed down river valleys to the sea, some 125 miles away. Many of the victims were never found. |