Yellowstone volcano eruptions caused 80-year winters, researchers say

Yellowstone volcano eruptions caused 80-year winters, researchers say


As winter approaches, take heart in the fact that it won’t last 80 years.

That’s how long two volcanic winters may have lasted after two separate explosions of the Yellowstone volcano about 630,000 years ago, the same eruptions that formed the Yellowstone caldera, and the last big eruptions of the volcano. The explosions occurred about 170 years apart and helped drop the ocean surface temperature by about 5.4 degrees.

These conclusions are the result of a detailed examination of sediments collected in Santa Barbara Basin, off the Southern California coast. By drilling into the basin’s mud, scientists from the University of California Santa Barbara could see the individual layers on an almost decade by decade basis, an amazingly detailed view.

Their research was revealed in a press release from the Geological Society of America last week.

Grabbing headlines

Mention Yellowstone and volcano in the same sentence and news feeds hum, Facebook lights up with frightening posts and some websites hype a foreboding end to life on Earth. Especially in the past few months, Yellowstone’s supervolcano has garnered several such headlines.

First came a swarm of earthquakes, mostly small, that spawned theories of an impending eruption. Earthquake swarms are common in the area, hitting as many as 3,000 in 1985. The cause is either changing stresses in the vicinity of the 1959 Hebgen Lake earthquake, or it could be water or magma moving around under the surface, according to Mike Poland, a geophysicist with the U.S. Geological Survey and the scientist in charge of the Yellowstone Volcano Observatory.

This summer’s log of earthquakes was high at 2,500, but Poland pointed out that the seismic infrastructure monitoring the Greater Yellowstone Area is also much more sensitive and yet may still be missing some smaller, more localized temblors.

Another story that grabbed attention said that NASA scientists had studied how to inject cool water into Yellowstone’s magma chamber to depressurize the system and halt an eruption, according to the BBC. The system could use venting steam to power turbines, a double benefit.

Quicker refill

Other recent headline-capturing stories have been based on a scientific study that, taken out of context, was used by some websites to create doomsday scenarios.

Arizona State University graduate student Hannah Shamloo, who analyzed fossilized volcanic ash from Yellowstone, reported that an injection of fresh magma into a system like Yellowstone’s — enough to cause a supereruption — could happen in decades rather than thousands of years.

“It’s shocking how little time is required to take a volcanic system from being quiet and sitting there to the edge of an eruption,” Shamloo told The New York Times.

That statement was qualified, though, with the footnote that there’s more work to do before scientists can verify a precise time scale.

Poland happened to be in the Yellowstone backcountry when that story appeared, requiring his predecessor to field calls on the subject from the national and international media. Although Poland has worked in Hawaii where volcanic eruptions can generate a lot of local interest, he said he was surprised by the “intense media focus” related to Yellowstone.

“There’s a psychology to this I didn’t expect,” he said, “which has me wanting to get more information out to the public, because it seems like the public really eats it up.”

Geyser gazers

An example of the continuing public interest Yellowstone’s plumbing can generate also came in October when University of Utah scientists published a report providing a better picture of the underground workings of Old Faithful geyser and the surrounding geyser basin. By using seismic sensors to capture faint vibrations, the researchers were able to map the hot water reservoir that supplies water to the geyser.

“The neat thing about these geyser systems is they are repeat experiences,” Poland said. “Assuming the plumbing doesn’t change, they can deploy in one area, move to another and see the same process to map out the plumbing system.”

The scientists estimated that the underground hot water reservoir — which is really a system of cracks and fractures rather than one large pool — has a diameter of about 200 meters, “a little larger than the University of Utah’s Rice-Eccles Stadium, and can hold approximately 300,000 cubic meters of water, or more than 79 million gallons,” according to a university press release.

By comparison, each eruption of Old Faithful releases around 8,000 gallons, leaving a lot in reserve.

“Although it’s a rough estimation, we were surprised that it was so large,” said doctoral student Sin-Mei Wu, the first author of the research.

Old Faithful got its name because it regularly erupts about every 44 to 125 minutes.

Back to mud

Old Faithful’s eruptions are like seconds on the geological time scale when compared to the data analyzed in the mud of the Santa Barbara Basin. Poland said although the findings are intriguing, he’s going to hold off on endorsing the evidence until it can be reconciled with other information found around Yellowstone.

“I don’t know much about the offshore geology,” he said. “But even if it is only a couple of hundred years, I think you would see it in the stratigraphy that was mapped in Yellowstone. It could be completely consistent.”

U.C. Santa Barbara geologist Jim Kennett, who led the study, said the evidence was so apparent because of the basin’s unique formation. About 1 millimeter a year of sediment is deposited into the basin, which is fed nutrients from the ocean that include tiny shellfish. The shells preserved in the sediment are a record of oxygen isotopes from which scientists can deduce the sea surface temperature when they were alive.

Oxygen levels on the bottom of the basin are so low that no mud-dwelling marine animals live there, animals that could burrow into the mud and mix up the sediment layers.

“Thus, it is not surprising that Kennett and his group can look in detail at the climate changes following a volcanic eruption,” Cathy Whitlock, a Montana State University professor whose Paleoecology Lab has used sediment cores from mountain lakes to track fire and climate history in the West, wrote in an email.

“Their study gives us insight into a period that is generally poorly known,” she added. “It was a time of tremendous change in our region, with the eruption of the Yellowstone supervolcano, which was likely a series of closely spaced eruptions.”

So cold

Each volcanic winter lasted longer than it should have, according to simple climate models, Kennett said in the news release.

“We see planetary cooling of sufficient magnitude and duration that there had to be other feedbacks involved.” The feedbacks might have included increased sunlight-reflecting sea ice and snow cover or a change in ocean circulation that would cool the planet for a longer time.

Such findings didn’t surprise Whitlock.

“We saw cooler temperatures around the world as a result of the Mount Pinatubo eruption in the early ’90s,” she wrote. “This was due to the ejection of particulates and sulfides in the atmosphere. It sounds like this group is seeing a similar but greater cooling impact from the Yellowstone eruptions, which would have been many times larger.”

If the research holds up, Poland said volcanologists will have to adjust their models.

The ability to examine an event so long ago based on layers of sediment in a basin in California is fascinating to Poland and just one more example of how continuing technological evolution is painting a broader picture of ancient events, and giving greater insight into the functioning of the Yellowstone caldera and its unique geology, tales of which are always good for a headline.


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