Not in a million years, says Oregon geologist about Yellowstone eruption

After probing volcanic fields of the Yellowstone hotspot track, University of Oregon geologist Ilya N. Bindeman says a massive, climate-altering volcanic eruption, "probably somewhere in Montana," is at least a million years away.

A May 13, 2013, volcanic eruption in EcuadorIn his projection, however, Bindeman, adds a disclaimer that "everything is possible in geology but interpretations are not always very precise." The last eruption occurred 640,000 years ago at a site inside what is now Yellowstone National Park. His research points to a recycling process in magma genesis that takes approximately two million years.

Bindeman, a native of Russia, began studying super volcanoes before joining the UO faculty in 2004 in the Department of Geological Sciences, where he built a state-of-the-art stable isotope laboratory.

Since March 2009, his focus under a five-year National Science Foundation CAREER award has been on the Yellowstone hotspot, but he's also studied sites in Iceland and Russia's Kamchatka Peninsula.

Ilya Bindeman, geological sciencesHis grant (No. 0844772), now in its final year, has produced some 25 published papers. It also has supported educational opportunities for undergraduate students, graduate-level researchers, postdoctoral scientists and international collaborators. He also has hosted international visitors on campus and in the field, including a recent two-week Yellowstone field school for scientists and graduate students from Switzerland and Russia.

Most recently, Bindeman's team has probed trace minerals in rhyolites — igneous rocks rich in silica — expelled in eruptions in the Yellowstone hotspot that runs from southwestern Idaho to Yellowstone National Park in northwestern Wyoming and near the southwest tip of Montana. Only the northeastern portion of this track is considered active.

The hotspot forms a conveyor-belt sequence of caldera clusters due to the North American plate moving at a rate of two to four centimeters (.8 to 1.6 inches) a year over a plume of hot mantle beneath Earth's surface. This process involves continuous interaction between Earth's crust and basalt that creates large underground chambers of magma that feed explosive caldera-forming eruptions.

In recent papers, a very distinct pattern of caldera recycling has emerged. Just published work led by graduate student Dana Drew documented the geochemistry of the Picabo portion of the chain (see the news release: "Crystals in Picabo's rocks point to 'recycled' super-volcanic magma chambers"). In 2011 and 2012, doctoral student Kathryn Watts, now the Mendenhall Postdoctoral Research Fellow on a volcano hazard team at the U.S. Geological Survey in Menlo Park, Calif., led two papers on the Heise portion northeast of Picabo.

These projects shed new insights into eruption cycles that contradict the predictions often played out in the media, Bindeman says.

"If you look at the past record of volcanic eruptions in the last three to 10 million years, a periodicity emerges," he says. "For example, in the last three million years there have been three caldera-forming eruptions, spaced about 650,000 years apart. If you assume the last eruption of Yellowstone happened 640,000 years ago, we should have a similar-sized eruption soon. That is the kind of news story that is periodically released, providing a cataclysmic doomsday scenario."

Bindeman says hold on. "Yellowstone is currently active, so if you want to know what is going to happen at Yellowstone, we need to understand what the Yellowstone plume was doing in the past," he says.

"The Heise cycle started 6.6 million years ago and ended 4 million years ago. Dana's new study has covered the third-oldest caldera cycle, Picabo, which started about 10.4 million and ended 6 million years ago, so before Heise. These studies provide detailed geochemical analyses of the complete cycles associated with these volcanic fields," Bindeman says.

Uranium-lead dating of the zircons and an analysis of isotopic changes, especially oxygen and hafnium, in the rocks at both Heise and Picabo have helped Bindeman's lab unravel "the story of magma genesis — how magma was produced over the entire three caldera cycles."

Bindeman's team and international collaborators have found pervasively and abundantly depleted levels of oxygen in the rhyolites in all three calderas, accompanied by increasing isotopic diversity in zircons — the result of alteration trigged by rain and snow, which geologists refer to as hydrothermal alteration. These rocks are buried and eventually remelted with heat provided from below, forming diverse magma batches in the upper crust.

"Our research shows there is a significant proportion of volcanic recycling increasing through time in all three caldera clusters," Bindeman says. "New magmas coming into the crust are not just the result of new production from the Yellowstone plume, but rather the result of recycling and remelting of pre-existing materials that have undergone hydrothermal alteration near the surface. Surviving recycled zircons, provide us with evidence of the source rock that was remelted, as well as the batch assembly process that assembled the super-volcanic magma body."

At this stage, when diverse zircons are produced, it indicates that magmas are recycling a volcano's own roots, he says. "There are very few rocks that can be melted to produce fresh magma. In investigating the cycles of Heise, Picabo and Yellowstone, we discovered that at the end of the magma-system evolution, these recycled zircons are present."

This "periodicity," Bindeman says, between caldera-forming eruptions in the Yellowstone hotspot track is segmented, not a single progression. In each caldera cycle, a two-million-year buildup of magma leads to a series of eruptions in the same location, each followed by recycling of buried rocks that have suffered varying degrees of hydrothermal alteration," he says.

"We think Yellowstone is on a dying cycle, because three calderas have happened and collapsed, recycling of erupted material has already occurred, and there are low levels of magma being produced," Bindeman says. "We think Yellowstone will continue to produce magma as its been doing for the past 600,000-plus years, after the last caldera-forming eruption. We also suggest that a new eruption may happen somewhere in Montana after the North American plate moves enough to expose fresh fertile crust for melting. But this is unlikely to happen for the next million years or so."

Bindeman and his postdoctoral researcher Erwan Martin also have investigated the potential effect of a massive volcanic eruption on the atmosphere. "When eruptions happen, large amounts of ash and gases, including sulfur dioxide, enter the atmosphere," Bindeman says. "When sulfur dioxide gets oxidized into sulfuric acid, it results in global cooling and ozone destruction, but scientists don't yet know the absolute effects on the ozone layer destruction and how much global temperatures will change."

The consequences often last for decades, he adds, "and we are trying to investigate this problem by analyzing a rare isotope of oxygen — oxygen 17 — in volcanic ash."

Bindeman earned a doctorate from the University of Chicago in 1998. Before coming to Eugene, he held postdoctoral and staff scientist positions, respectively, at the University of Wisconsin and California Institute of Technology.