Yellowstone National Park, located in Wyoming, lies above the Yellowstone Supervolcano.
There are other "supervolcanoes" across the world, including the large caldera volcanoes of Japan, Indonesia, and South America.
The Yellowstone Caldera was formed after three super eruptions took place over the past 2.1 million years.
These include the Huckleberry Ridge eruption 2.1 million years ago, the Mesa Falls eruption 1.3 million years ago and the Lava Creek eruption around 630,000 years ago, which created the Yellowstone Caldera and the Lava Creek Tuff.
Can scientists predict when Yellowstone will erupt?
Scientist do not know when Yellowstone will erupt again.
There is also no evidence has an eruption or any size is due any time soon.
If there was going to be a catastrophic eruption at Yellowstone, it is not likely to occur in the next few centuries.
Could Yellowstone erupt again?
Visitors travel from all over the world to see the volcano
Scientists at the Yellowstone Volcano Observatory (YVO) already closely watch the Yellowstone area for warning signs or any changes that could result in an eruption.
They monitor Yellowstone for signs of volcanic activity by using seismographs, which detect earthquakes, and GPS to detect ground motion.
As science and technology has developed significantly over the last 25 year, most scientists think the lead up to a devastating eruption could be predicted weeks or even months or years in advance, according to USGs.
There would supposedly be warning signs similar to other volcanic eruptions, such as earthquake swarms and rapid ground deformation that usually takes placed weeks before.
A map shows Yellowstone's activity
Yellowstone, like many other caldera systems around the world, occasionally has small earthquakes, ground uplift. subsidence and gas releases.
However, this does not mean there will be an eruption.