A new study into supervolcanoes has found that they may be more prone to sudden devastating eruptions than previously thought.
The giant volcanoes are fuelled by huge pools of magma - molten rock - deep below the earth's surface, which geologists had believed built up over hundreds of thousands of years, the BBC reports.
The new study suggests that the process may be much quicker. Geologists say a giant magma chamber under Yellowstone National Park in the United States has been swelling at a record rate since 2004.
If it were to erupt, they believe it could cause devastation 1000 times more powerful than the Mount St Helens eruption in 1980.