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Long - quiet vent in the Cascades region of the Pacific Northwest are still underpin by large reservoirs of magma , new inquiry line up .
The finding have implications for monitoringvolcanoesprior to eructation , the researchers wrote in their paper , publish Jan. 23 in the journalNature Geoscience .
Dormant volcanoes in the Cascades mountain range have large magma reservoirs sitting beneath them, scientists discover.
Scientists have debated whether magma can persist in the upper gall under volcanoes for tenacious period or whether it moves into these shallow regions curtly before an eruption . The young study suggest that , at least in the Cascades , these magma reservoirs last thousands of years without causing an eruption .
" Regardless of eruption frequency , we see large magma bodies beneath many volcanoes , " study first authorGuanning Pang , a postdoctoral investigator in Earth sciences at Cornell University , said in astatement . " It seem that these magma bodies exist beneath vent over their whole lifetime , not just during an active state . "
The magma chambers discovered in the current survey are n’t poised to cause disaster , however ; all are only partially melted , without enough liquid dowry to trigger off an eruption .
Related : What ’s the conflict between an fighting , sleeping and extinct volcano ?
The young findings make out courtesy of an raise to U.S. Geological Survey seismic monitoring stations in the Cascade Mountains , which allow Pang and his co - author to cover the waves of distant earthquakes as they traveled beneath Mount St. Helens , Mount Rainier , Lassen Peak and other nearby vent . They noticed a ordered retardation of the earthquake wave speed — sometimes by as much as 70 % — under the volcanic crown .
These slowdowns are too large to be explained by agent such as temperature , the researchers save . Waves move more slowly through liquid than they do through solids , so the finding hint that big magma reservoirs lurk about 3 to 9 Swedish mile ( 5 to 15 kilometers ) below the surface . They detected these reservoirs below Mount Rainier , Mount St. Helens , Mount Hood , Newberry Volcano , Crater Lake and Lassen Peak .
Three Sisters and Mount Shasta did not show like patterns , but that could have been due to a deficiency of seismic measurements , the investigator wrote . puffiness of the ground near Three Sisters in late twelvemonth does indicate there is magma moving in the area .
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Magma reservoirs are n’t like underground lakes of fervency . Rather , they ’re made of porous rock through which liquid magma moves . Only when the portion of fluid magma goes over 35 % does the reservoir have the potential to erupt . Pang and his colleagues do n’t have verbatim measure of what percentage of the magma below these heap is melted , but they calculated that it could range from 3 % to 32 % .
Even if the melting were as high as 32 % , it does n’t inevitably foreshadow an blast , as this percentage could defy study for decades or decline , depending on local conditions . In either case , scientist do not see any evidence that these reservoirs are primed for an eruption , such as an uptick in earthquakes .
The Cascades are specially well monitored , but scientist have little hint of what ’s going on below most volcanoes in the world , the researchers said . Similar method acting that habituate seismal stations could help provide a better motion-picture show of what lies beneath vent around the world .
" If we had a better general understanding of where magma was , we could do a much better chore of targeting and optimize monitoring , " study senior authorGeoffrey Abers , an Earth scientist at Cornell University , said in the financial statement .
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