The enormous volcano sitting beneath Yellowstone National Park could erupt sooner than previously expected, scientists studying the area say.

Analysis of minerals in fossilised ash has determined that during previous eruptions there were changes in temperature in the run-up that occurred much more quickly than previously thought.

A powerful eruption occurred roughly 630,000 years ago, according to National Geographic, shaking the region and creating the Yellowstone caldera — a bowl about 40 miles wide the encompasses much of the park.

The volcano is so big that a major eruption may choke the Earth's atmosphere with ash.

Researchers at Arizona State University analysed evidence from that eruption, and believe that the super-volcano was awoken after two influxes of fresh magma flowed into the reservoir beneath the caldera.

But, while the volcano could have devastating consequences if it were to erupt, nobody need worry just yet. The accelerated timeline shows the temperatures around the volcano increased over a period of decades, instead of the centuries scientists had previously believed the process would take.

"It’s shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption,” Hannah Shamloo, the study’s co-author, told the New York Times.

So, what would happen if volcano were to erupt tomorrow? Depending on the size of the eruption, the volcano could cover major portions of the United States in dangerous ash, and the Earth’s atmosphere would likely be filled with that same ash.

Yellowstone's grand prismatic sping is beautiful