Yellowstone National Park is famous in the volcanology community for being the site of three explosive supereruptions, the last of which was 631,000 years ago. During that eruption, approximately 1000 cubic kilometers of rock, dust, and volcanic ash blasted into the sky. Debris rained across the continental United States, spanning a rough triangle that stretches from today’s Canadian border down to California and over to Louisiana. In places, ash reached more than a meter thick.
At IAVCEI 2017 [International Association of Volcanology and Chemistry of the Earth’s Interior] in Portland, Oregon, researchers presented evidence that such eruptions only need a few decades of gestation before exploding.
“If something like this happened today, it would be catastrophic,” says Hannah Shamloo, a geologist at Arizona State, speaking to the American Geophysical Union. “We want to understand what triggers these eruptions, so we can set up warning systems. That’s the big-picture goal.”
Alongside her Ph.D. adviser at Arizona State, geologist Christy Till, Shamloo examined two specific sorts of crystals known as phenocrysts, which form as magma cools a beneath a volcano. Varying between 1 and 2 millimeters each, these crystals are too large to have formed during the heat of an eruption. Rather, each crystal starts with a core that grows layer upon layer, forming a rough equivalent to the rings of a tree.
The early evidence, presented at a recent volcanology conference, shows that Yellowstone’s most recent supereruption was sparked when new magma moved into the system only decades before the eruption. Previous estimates assumed that the geological process that led to the event took millenniums to occur.
To reach that conclusion, Hannah Shamloo, a graduate student at Arizona State University, and her colleagues spent weeks at Yellowstone’s Lava Creek Tuff — a fossilized ash deposit from its last supereruption. There, they hauled rocks under the heat of the sun to gather samples, occasionally suspending their work when a bison or a bear roamed nearby.
A volcano the size of Yellowstone is essentially a gigantic heat generator, equivalent to six industrial power plants. Yellowstone currently leaks about 60-70% of the heat coming up from below into the atmosphere, via water which seeps into the magma chamber through cracks. The remainder builds up inside the magma, enabling it to dissolve more and more volatile gases and surrounding rocks. Once this heat reaches a certain threshold, then an explosive eruption is inevitable.
Nasa have conceived a very different plan. They believe the most viable solution could be to drill up to 10km down into the supervolcano, and pump down water at high pressure. The circulating water would return at a temperature of around 350C (662F), thus slowly day by day extracting heat from the volcano. And while such a project would come at an estimated cost of around $3.46bn (£2.69bn), it comes with an enticing catch which could convince politicians to make the investment.
“Yellowstone currently leaks around 6GW in heat,” Wilcox says. “Through drilling in this way, it could be used to create a geothermal plant, which generates electric power at extremely competitive prices of around $0.10/kWh. You would have to give the geothermal companies incentives to drill somewhat deeper and use hotter water than they usually would, but you would pay back your initial investment, and get electricity which can power the surrounding area for a period of potentially tens of thousands of years. And the long-term benefit is that you prevent a future supervolcano eruption which would devastate humanity.”
The idea is to drill in from the supervolcano from the lower sides, starting outside the boundaries of Yellowstone National Park, and extracting the heat from the underside of the magma chamber. “This way you’re preventing the heat coming up from below from ever reaching the top of the chamber which is where the real threat arises,” Wilcox says.
Cooling Yellowstone in this manner would happen at a rate of one meter a year, taking of the order of tens of thousands of years until just cold rock was left.