Magma expanse under Yellowstone supervolcano more vast than thought

As tourists stroll between Yellowstone's 300 active geysers, taking selfies in front of thousands of bubbling, boiling mud pots and hissing steam vents, they are treading on one of the planet's greatest time bombs. The park is a super volcano so enormous, it has puzzled geophysicists for decades, but now a research group, using seismic technology to scan its depths, have made a bombshell discovery.

http://www.cnn.com/2015/04/24/us/yellowstone-supervolcano-magma-reservoir-discovery/index.html