The caldera inside Yellowstone National Park is dubbed a supervolcano due to its capability to inflict devastation on a global scale in the event of a supereruption. It was formed during the last three big events – the Huckleberry Ridge eruption 2.1 million years ago, the Mesa Falls eruption 1.3 million years ago and the Lava Creek eruption approximately 630,000 years ago. Located below the states of Wyoming, Montana and Idaho, the area is constantly monitored by the USGS (United States Geological Survey) for signs that history could repeat itself.
And they have pulled in help from NASA, too.
Preventing volcanoes from erupting is beyond human control, but scientists can monitor them for signs that one is on the way through changes in heat at ground level.
USGS scientist Greg Vaughan explained: “The National Park Service (NPS) monitors these features and how they change.
“They disappear and move around. New ones pop up where they have never been before.
“The NPS needs to understand how this ever-changing thermal activity affects visitor safety, and park infrastructure – for example, if they are going to build a new road.
“Thermal anomalies often precede eruptions, but it is usually after the fact that we realise this.”
While the park has placed sensors at some locations, it is impossible to monitor on foot more than 10,000 geothermal features spread over 3,472 square miles.
Dr Vaughan added: “For a lot of volcanoes, a satellite image might be the first indication of an eruption.”
In 2013, Dr Vaughan thought that Yellowstone would make a good case study for detecting thermal precursors of an eruption.
Yellowstone’s high elevation, ranging from 5,000 to 11,000 feet, gives its thermal features a cool background, especially at night when the Sun is not warming the surface.
The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, attached to both the Terra and Aqua satellites passes Earth twice a day.
This high frequency of data is ideal for monitoring larger features, but not for small ones like geysers.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), which is also onboard the Terra satellite can produce thermal images at 90-metre pixels, but ASTER does not acquire data constantly, only on request.
Dr Vaughan used a mixture of both satellites to measure the background temperature of the Yellowstone area.
This gave him data on normal surface temperatures in the area over the last decade to compare with more recent ground instruments and airborne records.
The heat data confirm that Yellowstone’s volcano remains largely unchanged.
Dr Vaughan added in July: “Over the years we’ve been looking, there has not been any real change.
“There are variations on a smaller scale, but for the park as a whole, no detectable thermal changes.
“That question is really only answerable over a longer time scale.
“ASTER has been useful for assessing and updating maps of specific thermal areas in the park.
“We found hot areas with ASTER that were not on the thermal area maps.”
The study provides a framework for monitoring changes in these subtle features, which might someday be automated to alert scientists of any major changes.