When Washington State ’s Mount St. Helens break through in 1980 , the 57 resulting death were the most show for a volcanic eructation in the United States . Yet a report has warned these could be a tiny fraction of the true toll if nothing is done to harness the bequest the outburst left behind . The danger lies in catastrophic deluge that could be unleash through a failure of a natural dike created during the eruption .
When St. Helens blew its top , it triggered an avalanche that dam up the Toutle River . Water could no longer drain from Spirit Lake , produce the piss story . If this dam was to neglect on the spur of the moment , the flood that would sweep down the river system would imperil 50,000 people living downriver .
gang fight from St. Helensearlier this yeargained attending as an meter reading the mountain might be about to erupt again . That seems to have been a untrue alarm clock , but even if it was veridical , the ash tree and lava of a repetition of the 1980 explosion would be unlikely to bring forth anything like the scathe of failure by the Spirit Lake dam .
Such a failure is , unfortunately , a real hazard . The pressure of water can cause decameter to tumble , and the location ’s high sediment burden increase the chances of this , particularly given the frequent outpouring from eminent up the batch . Moreover , given its law of proximity to theCascadia Seismic Zone , and the local shaking from even little eruptions , earthquakes are to be anticipate .
The report recommends fix to the tunnel and to sediment retention structures above the dam . It also suggests consideration be given to the origination of a spillway or a second drainage burrow .
As unsafe as the Spirit Lake Dam is , it has nothing on another natural blockage half a world aside . In 1911 an earthquake in Central Asia triggered a landslide that obturate the Murghab River and formedSarz Lake . The lake is hundred of meter deep , and if the dike were to fail as a result of a new seism , the resulting rampart of pee would pass over out 28 villages in the valley below . In the worst case scenario , more than 5 million people living further downstream would be in risk . Geologists disaccord , however , on the likelihood of such an event .
