Hundreds of small tremors have shaken the area near the sleeping Yellowstone supervolcano, with more than 200 tremors detected in 10 days.
Experts from the US Geological Survey say that the ‘swarm’ began on February 8, roughly eight miles northeast of West Yellowstone, Montana.
Supervolcano eruptions are a terrifying destructive force – which can blanket huge areas in ash and change the climate for decades.
If the volcano erupted, it could be a thousand times as powerful as the 1980 Mount St Helens eruption, experts have warned.
But volcano experts say there’s no reason to worry – the risk of an eruption remains low (classified at ‘normmal’), and the Yellowstone supervolcano has not erupted for 72,000 years.
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University of Utah seismograph stations picked up the quakes last week, counting more than 200.
The United States Geological Survey said, ‘‘The present swarm started on February 8, with a few events occurring per day.’
‘On February 15, seismicity rates and magnitudes increased markedly. As of the night of February 18, the largest earthquake in the swarm is M2.9, and none of the events have been felt. All are occurring about 8 km (5 mi) beneath the surface.’