Yellowstone volcano is believed to have had three cataclysmic eruptions over the last two million years. The last of these caldera-forming blasts went off around 640,000 years ago and shaped Yellowstone’s current landscape. Today, Yellowstone volcano remains active but there is no immediate threat of another super-eruption in the foreseeable future. And yet despite this, scientists scan the supervolcano for ground deformation, which could be a sign of intense magma movement deep beneath the surface.
Geologists keep track of ground deformation at Yellowstone with the aid of GPS stations and satellite-based technology known as InSAR.
InSAR or Interferometric Synthetic Aperture Radar is a technique, which uses radar images of the Earth’s surface collected by orbital satellites.
According to the US Geological Survey (USGS), InSAR is an effective measurement tool because radar waves beam down through most weather conditions – a big “advantage during a volcanic crisis”.
The first of these satellites, the ERS-1, was launched into space by the European Space Agency (ESA) in 1991.
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The so-called synthetic-aperture radars (SAR) satellite was tasked with snapping radar scans of the entire planet.
And just two years into its mission, the satellite had already proven its usefulness during a major earthquake in California.
Dr Dan Dzurisin, a USGS geologist, explained the benefits of the technology in the weekly Caldera Chronicles column.
He said: “A remarkable demonstration of InSAR’s capability came in 1993 when several French scientists produced an interferogram from ERS-1 images showing in glorious detail the pattern of surface disruption caused by the 1992 magnitude 7.3 Landers, California, earthquake.
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“In the decades prior, geologists had measured fault scarps, geodesists had surveyed nearby benchmarks, and modellers had calculated how the Earth might move during a major earthquake.
“For the first time ever, all could marvel at a ‘picture’ of what actually happened.
“It was a snapshot taken from space by a satellite designed to do something else.”
According to Dr Dzurisin, technology like InSAR can spot minuscule differences in ground deformation with “millimetre-scale precision”.
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This can help geologists map out changes in the landscape without having to trek across mountains with handheld instruments.
He said: “Today, scientists are using InSAR, the ‘magic deformation camera’ to study deformation at Yellowstone and elsewhere around the globe.
“Using this technique, it has been possible to get an overall picture of Yellowstone deformation, revealing some interesting patterns of ground motion.”
A good understanding of Yellowstone’s ground deformation could potentially give the USGS clues and forewarnings about future volcanic and tectonic events.
On average, the Yellowstone volcano goes up and down by three to five inches a year.
Geologists first began to actively monitor ground movement at Yellowstone in the 1970s.
The USGS noted a period of rapid rise and fall in ground levels between 2004 and 2010 but none of the events suggested an eruption was brewing.
The agency said: “Yellowstone clearly can move up and down regularly without erupting.”