Underneath Yellowstone National Park in Wyoming, Montana and Idaho, there is a reservoir of magma that is more than twice the size that researchers previously thought. It’s not getting bigger. It’s just that new technology has made the ability to see it better. This will also have implications on the extent of the volcano’s impact when it erupts. Researchers with the U.S.G.S. say that the last time the volcano erupted was some 640,000 years ago. They also say that this supervolcano has the potential to spew more than 240 cubic miles of magma across Montana, Idaho and Wyoming with global effects. Scientists do believe that it will erupt again one day, but do not know when.

Since Yellowstone is located in a seismic active zone, little tremors occur often. However, seismologists believe that one day there will be a strong earthquake, like the 7.3 that hit the area in 1959. When measuring the reservoir, scientists discovered that it is tilted from northwest to southeast. It is measured by 55 miles by 20 miles on each side and is about and about 6 miles deep, which scientists say is roughly the same size as it was when it last erupted thousands of years ago. Scientists believe that when the volcano erupts, the reservoir will be emptied. It will then take a long time to refill.

Scientists believe that this eruption will have global consequences as large amounts of ash and pulverized rock will be thrust into the atmosphere and fall back to earth. Volcanic ash and material will linger in the atmosphere, blocking out the sun, causing global temperatures to lower (which would affect climates around the world).

Before you get alarmed, scientists say that the chance of a super-volcano erupting in Yellowstone is quite small; 1 in 73,000 to be exact. The more imminent threat from this area would be from a large earthquake like the one in 1959.