Probing the Yellowstone caldera: Do low temps decrease chances of future eruption?

It is a sure way to generate some cheap page views: declare the end of the world is nigh and proclaim that an eruption of the supervolcano underneath Yellowstone National Park will the catalyst of a world-ending catastrophe.

That’s the news that came our way from an Indian website we’d never seen before:

“Yellowstone National Park in United States is famous for its thermal springs and old faithful geyser. The reason for this is simple — it’s sitting on top of the world’s biggest volcano and geological experts are beginning to get nervous sweats. The Yellowstone volcano has a pattern of erupting every 650,000 years or so, and we’re many years overdue for an explosion that will fill the atmosphere with ash, blocking the sun and plunging the earth into a frozen winter that could last up to 15,000 years. The pressure under the Yellowstone is building steadily, and geologists have set 2012 as a likely date for the big bang.”

Well, that’s great for anyone trolling for page views (Google the wording if you want; we’re not going to dignify such tripe with a link). But there are so many errors here it’s hard to say where we should begin, but we’ll start with one: if anything, the supervolcano underneath Yellowstone National Park may be on its last legs, gradually cooling over time — which means it’s less likely to blow any time soon.

The evidence is clear: according to a study conducted by Derek Schutt of Colorado State University and Ken Dueker of the University of Wyoming, the Yellowstone supervolcano is only at 2640 degrees Fahrenheit (1450 degree Celsius) at 50 miles below the Earth’s surface. And while that seems really hot, it’s actually fairly cool for a supervolcano — lukewarm at best.

Now, Schutt and Dueker didn’t actually drill 50 miles and throw down a termometer: they extrapolated that temperature by taking seismic readings at the Snake River Plain, southwest of the Yellowstone caldera. Or, scientifically speaking:

“Recent studies show that the Yellowstone hotspot is associated with a plume-like low-velocity pipe that ascends from the transition zone to the lithosphere-asthenosphere boundary, where the plume is sheared to the southwest by North American plate motion. Rayleigh wave tomography shows this plate-sheared plume layer has an extremely low S wave velocity of 3.8 ± 0.1 km/s at 80 km depth, ~0.15–0.3 km/s lower than the velocity observed beneath normal mid-ocean ridges. To constrain the temperature of the plume layer, a grid search with respect to grain size and temperature is performed to fit the observed Rayleigh wave phase velocities. This search finds that the excess temperature of the plume layer is >55–80 °C at 95% confidence for two different temperature-velocity and two different melt-velocity models, confirming that a thermal mantle plume exists.” (From Geology.)

They then compared the measured temperatures to other known supercolcanoes, including a live one in Hawaii, and discovered that the Yellowstone supervolcano readings were lower. In fact, they speculated that the Yellowstone plume may now be disconnected from its source in the Earth’s core, leading to gradually subsiding temperatures and the end of Yellowstone as we know it someday. (But not in our lifetimes; it will take a very, very long time for the Yellowstone caldera to cool off — and we don’t know if their hypothesis is true.)

That doesn’t mean there’s no danger of the Yellowstone supervolcano blowing; historical evidence would indicate that we’re due for one within the next thousand years or so, diminished temperatures or not. And, of course, even a modest earthquake could upset the plumbing under Yellowstone to the point where an eruption is inevitable sooner or later. But that level of mystery is central to the mystique of Yellowstone National Park: despite the ageless geography of the Park, things could be totally different tomorrow, next year or next week.

About admin

Check Also

Paradise Valley

Victory for Opponents in Battle Against Gold Mining Exploration in Paradise Valley

Opponents of a proposed mine just north of Yellowstone National Park in Montana’s Paradise Valley won a …