When tourists stroll over Yellowstone’s 300 active geysers, they don’t understand that they are treading on one of Earth’s greatest time bombs.

The park itself is such a large super volcano, it has puzzled geophysicists for decades and with new discoveries using seismic technology, a research group has made a discovery.

Yellowstone’s magma reserves are greater than previously thought, say scientists from the University of Utah.

Discoveries of enough magma to fill the entire Grand Canyon 14 times over were published on Thursday in the journal Science. The large magma expanse is right under the park.

Yellowstone’s main heat source reaches down 440 to 1,800 miles beneath the Earth’s surface and comes from it’s molten core. It fuels the newly discovered reservoir of magma that lies on top of it.

The magma chamber lies on top of the reservoir. It is three to nine miles under the Earth’s surface and it fuels the geysers and steaming puddles.

The magma chamber alone has a volume of 2.5 times that of the Grand Canyon.

The massive bulk of magma cavities comprise of solid hot rock, which is hollow, and filled with pockets of liquified rock.

However, this discovery does not mean that there is any more magma than there was to begin with, the scientists say as well as having no signs of an imminent eruption.

“The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system,” said researcher Robert B. Smith.