Yellowstone volcano has super-erupted at least three times in its lifetime, with the most recent eruption around 640,000 years ago. The super-eruptions were driven by the volcano’s imposing magma chamber that stretches from 3.1 miles to 10.5 miles (5km to 17km) below the ground. According to the US Geological Survey (USGS), the raw source of heat under Yellowstone is one of the reasons why the ground around the volcano is rising. And looking for ground uplift at Yellowstone is critical, the agency said, because it could be a tell-tale sign of an eruption brewing deep underground.
The USGS said: “Because of the hotspot that lies beneath Yellowstone – and that supplies the heat needed to generate magma – the Yellowstone Plateau sits at a higher elevation than its surroundings.
“In essence, the region is buoyed upward by the heat beneath the surface.”
The ground around Yellowstone has also risen at the end of the most recent glacial periods, dubbed the Pinedale glaciation.
About 22,000 to 13,000 years ago, during the last ice age, the Yellowstone region was covered in a thick sheet of ice.
Yellowstone volcano: Heat under the supervolcano causes the ground in the area to rise
Yellowstone volcano: Yellowstone erupted three times in the past
Once all of the glacial ice melted away, the released pressure on the supervolcano caused the ground to rise.
The USGS said: “After melting of the ice, there was some uplift due to ‘rebound’ – basically, removal of the ice load caused the ground surface to buoy upward.
“This is actually still occurring in places like Greenland and Scandinavia, which were covered by epic ice sheets during the last major glaciation but it stopped Yellowstone thousands of years.
“Interestingly, there were no eruptions of magma after Pinedale glaciation.
“Studies of glacier melting in Iceland suggest that unloading due ice removal can cause melt formation and magma ascent, resulting in an increased number of volcanic eruptions.”
The region is buoyed upward by the heat beneath the surface
Another effect that contributes to the movement of ground at Yellowstone volcano is the tectonic activity of the North American tectonic plate.
Yellowstone volcano is located in a hotspot of activity near the North American plate and the Pacific Plate along the coast of West America.
As the plate drifts away to the southwest, the movement encourages the heat and molten rock to shoot upwards.
Uplift and subsidence of a volcanic system like Yellowstone can go on for tens of thousands of hundreds of thousands of years before an eruption occurs.
When Mount St Helens erupted in 1980, for instance, the volcano’s northern flank peaked by 262ft (80m).
In other cases, however, a volcano like the Long Valley Caldera in California has been rising at different points in the 1980s and 1990s without blowing.
The USGS said: “The Campi Flegrei caldera near Naples, Italy, had two episodes of uplift during 1970 to 1972 and again 1982 to 1984.
Yellowstone volcano: The magma chamber heats up the water features at the national park
Yellowstone volcano: The USGS monitors the supervolcano for activity
“The coast town of Pozzuoli, within the caldera, was raised 170cm (67 inches) and then 182cm (72 inches) out of the ocean during those two intervals.
“Each time, some subsidence followed the uplift, but no volcanic eruption has occurred.”
Thankfully, there are no signs that suggest Yellowstone will erupt again in the near future.
The supervolcano last blew up 640,000 years, 1.3 million years and 2.1 million years ago.
The USGS said: “There is no evidence that a catastrophic eruption at Yellowstone is imminent, and such events are unlikely to occur in the next few centuries.”