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It’s one of the internet’s favorite fears: That the giant supervolcano fast asleep beneath Yellowstone National Park will somehow rumble to life and put us all out of our misery. But while geologists have never seen it happen (the last supereruption was 631,000 years ago) and it’s unlikely to happen any time soon, they now have a pretty good sense of what they’d see—and they know they haven’t seen anything like it.
“Some volcanic systems just seem to be in a perpetual state of unrest, and Yellowstone is one of those,” Scientist-in-Charge at the U.S. Geological Survey’s Yellowstone Volcano Observatory told Newsweek. That unrest is scientifically fascinating, which is why researchers monitor the region from the ground and from space. And if a supervolcano eruption did somehow begin, Poland said, we’d definitely notice. “Man, the changes would be so much bigger than anything we’ve ever seen.”
Yellowstone’s hot springs are just one piece of its active geology.
In order for a supervolcanic eruption to begin, he said, a truly huge amount of magma would need to rise to the surface, and that would have very clear consequences. “You’ve got to break a lot of rock to move that much magma,” he said.
Scientists would be looking for three symptoms of that behavior in the data they gather from Yellowstone: an uptick in earthquakes, which would show up on seismic monitors; increased ground deformation as hot liquids slosh around below the surface, which scientists watch from satellites; and temperature changes in water features like geysers, which can be monitored remotely.
There’s another clue that’s helpful at other volcanoes, watching for increased amounts of gas coming out of the ground. But that wouldn’t be much help at Yellowstone, where unlike a traditional volcano that produces gas at a fixed point, Yellowstone’s releases would be spread over a huge area, making them difficult for scientists to spot.
That all sounds bad, sure, but the probability of anything big actually happening is tiny, Poland said. “Yellowstone is one of these examples of an extreme hazard but an extremely rare hazard as well.”
Earthquakes are a significantly more likely threat than an eruption. Although quakes are a signal of moving magma, they can also occur completely independently. At more delicate volcanoes, Poland said, a large earthquake might trigger volcanic activity, but Yellowstone is just too fast asleep. “It clearly hasn’t responded to any earthquakes in the last 70,000 years.”
This Yellowstone elk is totally calm about the park’s volcanic potential, and you should be too.
Nevertheless, Poland and scientists like him are keeping their eyes on seismological data and everything else they can gather about Yellowstone. And in a few years, scientists will have even better information to work from. That’s because NASA is working on a new radar satellite that will be better able to catch ground deformation, even when it’s hidden under vegetation.
“It has been a really eventful summer, we did have that large earthquake swarm and it really is one of the largest swarms we’ve detected over the last few decades,” Poland said. But that’s a reason to be curious, not afraid. “We’re going to learn something new about Yellowstone thanks to this swarm.”
Poland says it’s been a strange experience to study something that so many visitors fall in love with and so many internet-dwellers fear. He’s trying to find ways to encourage the former and reassure the latter. “Yellowstone is just not that close to erupting,” he said. “I’m far more worried about driving to work in the morning and getting offed in a car accident.”
YVO scientists were busy in October 2017. During that month, a number of field measurements were completed in Yellowstone National Park, and some instruments that had been recording data throughout the summer were recovered before the onset of the harsh Rocky Mountain winter. This included 12 semipermanent Global Positioning System (GPS) stations that had been in place since the spring—part of an annual campaign, now 10 years and still running, aimed at improving our understanding of how the ground deforms due to magmatic and hydrothermal activity in the Yellowstone region.
Together with frequent earthquakes, vigorous hydrothermal activity, and abundant emissions of volcanic gases, relatively slow movements of the ground surface attest to ongoing activity in the vast magmatic-tectonic system beneath Yellowstone National Park. Imperceptible to the naked eye, episodes of uplift, subsidence, and stretching or contraction of the surface are monitored by repeated surveys and networks of sensitive instruments operated by YVO and its partners. The process is called deformation because it changes the shape of the land surface in subtle but detectable ways. Since the first leveling survey along Park roads in 1923, the central part of the caldera floor has moved up nearly 1 meter (about 3 feet). But the uplift hasn’t been steady. Annual leveling surveys from 1983 to 2007 revealed periods of subsidence lasting up to a decade. More recently, scientists using a satellite radar technique called InSAR have discovered that both the pattern and rate of surface deformation change over time. Such movements are part of normal background activity at one of Earth’s largest active magmatic systems.
One of the tools that scientists use to keep track of surface deformation is the same GPS technology that you might use to navigate while driving your car. With specialized equipment and data processing techniques, the location of a GPS monitoring station can be measured very precisely, to within about 1 millimeter (less than the thickness of a dime). YVO and its partners, the University NAVSTAR Consortium (UNAVCO) and University of Utah, have installed a network of more than two dozen such stations in and around Yellowstone National Park to track surface deformation. The stations operate continuously, and data are processed at several locations to obtain daily positions. Small movements of the stations with respect to one another reveal the pattern of surface deformation over time.
The continuous GPS network cannot cover all areas in Yellowstone National Park, so YVO scientists have devised a less invasive GPS technique called semipermanent GPS (SPGPS). As the name implies, SPGPS stations are temporary. A network of SPGPS stations is installed each year from spring through autumn, avoiding months with heavy snowfall that can bury GPS antennas. This arrangement allows SPGPS stations to be smaller than continuous GPS installations—a distinct advantage in ecologically sensitive areas like Yellowstone. The trade-off, of course, is that SPGPS stations only acquire data when they are deployed. Despite the winter data gaps, SPGPS data have been useful for tracking movements of the caldera floor and an active area along the north caldera rim centered near Norris Geyser Basin. For example, on March 30, 2014, a magnitude 4.8 earthquake—the largest Yellowstone quake in 34 years—shook the Norris area. Nearby SPGPS stations that had been deployed only a few days earlier recorded a sudden reversal from uplift to subsidence that coincided with the timing of the quake. Combined with data from the continuous GPS network and InSAR observations, the SPGPS results helped to identify the location and depth of the deformation source. SPGPS may also prove useful for investigating the summer 2017 earthquake swarm north of West Yellowstone, MT. A SPGPS station at Horse Butte is only 15 km west of the swarm’s center. Analyzing the data from the station, which was recovered in late October, might prove useful to understanding the cause of the earthquakes and any associated ground motion. Stay tuned—we’ll post details about the 2017 SPGPS results to the YVO website over the winter!
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