Scientists are reporting that the supervolcano lying beneath Yellowstone National Park in the US is far bigger than was previously thought, stretching for more than 55 miles. Dr James Farrell from the University of Utah says the last major eruption took place 640,000 years ago, and added that previous examples are believed to have been 2,000 times the size of the 1980 eruption in Mount St Helens. However, Mr Farrell explained that he was certain no imminent eruptions would take place in the near future.