The warnings have been coming for a few years now. Yellowstone, the national park that we Americans treasure, is actually a supervolcano – one of the largest in the world – and it is coming due to explode. Now we know that there’s a lot more lava under the caldera that has the potential to flow in the future natural disaster.
This week, researchers at the University of Utah, who have been studying Yellowstone using a sort of improvised MRI thanks to seismography put in place to track earthquakes, published a paper with the first drawing of the lower magma chamber (the one below the chamber known to be full of hot, molten rock) along with estimates of the volume and just what is coming our way if Yellowstone decides to blow.
The new report fills in a missing link of the system. It describes a large reservoir of hot rock, mostly solid but with some melted rock in the mix, that lies beneath a shallow, already-documented magma chamber. The newly discovered reservoir is 4.5 times larger than the chamber above it. There’s enough magma there to fill the Grand Canyon. The reservoir is on top of a long plume of magma that emerges from deep within the Earth’s mantle.
This, people, is scary stuff. That’s a lot of magma. And it points to one extremely powerful volcano that seems to erupt every 700,000 years or so. Researchers think we are about 60,000 years away from the threshold of a major explosion, but like any other volcano, Yellowstone is unpredictable. The last less than catastrophic major explosion was 70,000 years ago.
According to scientists who have been studying Yellowstone for some time, it appears that the North American tectonic plate is slowly sliding to the southwest. As that happens, the earth’s crust slides over the hotspot under what is currently Yellowstone, and a caldera builds. There are a series of old calderas that can be seen in Oregon, Nevada, and Idaho that tell the story. This is more or less the same mechanism that is forming the Hawaiian islands as the Pacific plate slides and new volcanoes rise from the ocean floor. The seismography documenting earthquakes gives scientists a better understanding of that mechanism, and thanks to Yellowstone being seismically active, years of sensor data is readily available for analysis.
…tremors send seismic waves racing through the planet’s crust. Seismographs stationed around Yellowstone and across the United States record the arrival of these waves and carefully measure how long it took for them to reach the instruments. The speed of the waves carries information: When the seismic waves hit hot rock, they go slower; when they pass through cold rock, they’re faster. By combining the data from many sensors, scientists can get a picture of the hot and cold rock beneath Yellowstone. This is known as “seismic tomography.”
From that process, scientists got this graphic of what the earth’s crust looks like under the forming Yellowstone caldera:
The research is fascinating, if not more than a little scary considering the size of the blast zone for Yellowstone, but it is not going to a darn thing to stop the inevitable.
“This is like a giant conduit. It starts down at 1,000 kilometers. It’s a pipe that starts down in the Earth,” said Robert Smith, emeritus professor of geophysics at the University of Utah and a co-author of the new paper. The lead author is his colleague Hsin-Hua Huang….
“Really getting an idea of how it works and understanding how these large caldera-forming eruptions may occur, and how they might happen, would be a good thing to understand,” said paper co-author Jamie Farrell, another geophysicist at the university. “No one’s ever witnessed one of these really large volcanic eruptions. We kind of scale smaller eruptions up to this size and say, ‘This is probably how it happens,’ but we really don’t know that for sure.”
Far from being chicken littles sounding the alarm for an eruption that may or may not happen in our lifetimes, the researchers studying the Yellowstone Caldera and the mechanism of how the volcano works are giving future generations the tools they will need to watch the hotspot and know when it is time to evacuate.