A Chunk of Yellowstone the Size of Chicago Has Been Pulsing. Why?

Grand Geyser eruption. Photo:  Jacob W. Frank

An injection of magma under Norris Geyser Basin may be why the region is five inches higher today than it was 20 years ago.

Unusual Uplift at Yellowstone Volcano Was Caused by Magma Rising Up Deep Beneath the Surface, Study Finds

In 2013, an area of the Yellowstone supervolcano started rising at an unusually high rate. Over the next two years, it rose by over 5.9 inches per year—the highest rate of uplift ever recorded inside the caldera. What was behind this was unknown.

Everyone wants a picture with Old Faithful. But what many tourists don’t realize is that the hot springs and geysers of Yellowstone National Park are a constant reminder that 12 to 30 miles beneath the surface, there’s still an active volcanic system. And the Yellowstone Caldera, the expanse of supervolcano surface that takes up most of the park, is moving. Researchers from the U.S. Geological Survey published an article about Yellowstone’s uplift in January in the Journal of Geological Research—Solid Earth.

In the article, researchers highlighted two recent instances of uplift on the Yellowstone Caldera. One was in 2013–14, and another was in 2016. Both cases, researchers said, can actually be traced to underground magma movement from 20 years ago.

The entire Yellowstone Caldera is situated above a magma reservoir. Calderas themselves are products of eruptions, when underground magma chambers rapidly empty out and can no longer support the weight of the earth above them. Then, kind of like a deflating meringue, the ground depresses and forms a large crater-like sinkhole.
The Yellowstone Caldera is actually three calderas, the oldest of which is 2.1 million years old, and two resurgent domes. At 30- by 45-meters large, the mass is bigger than some countries, including Bhutan, Rwanda, and Puerto Rico. Sizable geographic changes tend to be hard to spot.

Thankfully, the Yellowstone Volcano Observatory is constantly monitoring the volcano and its surrounding area for changes beyond normal background movement. Recently, the group noted periods of uplift and subsidence, which formed the backbone of the USGA’s article. An area of the Yellowstone supervolcano began rising at an unusually high rate in 2013, lifting over 5.9 inches in the following two years. It might not seem like much, but for Yellowstone, it’s the highest uplift ever recorded.

Such epeirogenic movement can be traced back to the 1970s, when rapid uplift in the area was first noticed by researchers. They reevaluated their data on Yellowstone and found that the space had experienced 28 inches of uplift over the past five decades. After that, they’ve measured instances of rapid uplift and subsidence of the ground, as well as significant changes in hydrothermal features and earthquake activity.

The researchers theorized that the uplift and subsidence we’re seeing at Yellowstone now can be traced back to magma intrusion underground from 1996 to 2001. An excess of magma beneath the surface caused the ground to swell between 2013 and 2014. The rise paused when a magnitude-4.9 earthquake struck the area, then continued from 2016 to 2018.

Yellowstone’s epeirogeny also affects its hydrological features—the geysers and hot springs the park is famous for. Steamboat Geyser, for instance, the highest-erupting geyser in the world, has been erupting more frequently. It produced 32 eruptions in 2018 and a record 48 in 2019. The increased risk of hydrothermal events comes with shallow magma underground.

Steamboat entered similar moody phases in the 1960s and early ’80s, according to the Yellowstone Caldera Chronicles, published weekly by the Yellowstone Volcano Observatory. Thanks to those phases of increased eruptions, we know that it doesn’t mean anything for future volcanic activity at Yellowstone. Increased geyser activity isn’t anything to get paranoid about.

Still, not every geyser at Yellowstone is Old Faithful, literally named for being an easy hydrological phenomenon to predict. In the past decade, says John Ayers, professor of earth and environmental sciences at Vanderbilt University, “Steamboat has gone from as few as three days to as much as three years between eruptions.”

Thankfully, we can expect the surge in eruption frequency to continue into 2020. So if you’ve ever wanted to snap a photo of an impressive geyser that’s far less predictable than Old Faithful, this might be your year. Just keep in mind that far below your feet, there’s magma moving that will affect the geology of Yellowstone whole decades down the line.



The study was published in the Journal of Geological Research—Solid Earth.