Yellowstone Volcano's Norris Geyser Basin Has Risen

Yellowstone Volcano's Norris Geyser Basin has risen by 1.5cm over the last few months and scientists are not exactly sure why.

The uplift was recorded by a GPS monitoring station near the geyser and Michael Poland, scientist in charge of Yellowstone Volcano Observatory, said it appears to have started in July.

"We've been monitoring the Norris region with GPS since the early 2000s, and before that we were also using satellite radar to see how the ground near Norris was moving," he told Newsweek.

"Uplift there is not unusual. In 1996-2004 there was a major episode of uplift. The region returned to episodes of uplift in 2013-2014, and in 2015-2018. So it's very common."

The Yellowstone Caldera has been subsiding since 2015, but this deformation tends to pause during the summer months. The ground beneath the surface can be thought of as a sponge, Poland said. As snowmelt seeps in, the ground "puffs up."

The expansion of the ground stops the deformation for a short period, before subsidence resumes when the "sponge" drains.

At Norris, however, the cause of the uplift is unclear. In the monthly update from the Yellowstone Volcano Observatory, Poland said the changes could be a seasonal change, or it could relate to hydrothermal or magmatic processes taking place deep below the surface.

Hydrothermal fluids—water and gas—drive geyser and hot spring activity at the national park. These fluids contain dissolved minerals and when the water cools, the minerals drop out.

These minerals can then end up coating the subsurface pipes through which the water beneath the ground flows, similar to corroded pipes in a house. Changes to these conduits can then result in surface deformation.

This, Poland said, is the most likely cause of the uplift at Norris.

"There is a lot of hot water reaching the surface in that geyser basin. Norris is a dynamic place, with incredible geysers and amazing activity, and it's all because of the water that's moving around beneath the ground."

The uplift at Norris is relatively small. The largest uplift event in recent decades took place over 2013 and 2014, when the ground rose by 5cm in just four months. On March 30, 2014, there was a M4.8 earthquake at the site—representing the biggest earthquake at Yellowstone in almost 40 years. After that, the ground started to subside again.

Research into the episode later showed water that would normally have flowed through the subsurface near Norris had been accumulating.

"It was like a valve had been turned off, or something, and water was backing up," Poland said. "Like a kink in a hose. The earthquake was that valve breaking, and as soon as the valve was open once again, the water flowed out of the region and the ground subsided."

The last time magma was thought to be involved in uplift at the Norris Geyser Basin was between 1996 and 2004.

"This was occurring about 10 miles beneath the surface," Poland said. "It's not a sign that an eruption was more likely. Rather, it's a common process beneath Yellowstone. Magma hasn't reached the surface in the area in over 70,000 years, but the ground is always moving up and down."

norris geyser basin
Stock photo of the Norris Geyser Basin. GPS shows the area has risen by 1.5cm in the last few months. Getty Images