The renowned Yellowstone supervolcano is likely sustained by a completely different mechanism than many scientists had previously theorized. New research suggests that Yellowstone’s volcanic activity is actually driven by shifts within the Earth’s crust, rather than stemming from a deep magma reservoir beneath it, as was the long-held belief.
This finding could equip scientists with better tools to foresee future volcanic behavior and gain a deeper understanding of the volcano’s projected evolution.
“Our work alters the established view of how magma plumbing systems operate, meaning future eruption models must now incorporate this,” stated co-author Lijun Liu, a geologist at the Institute of Geology and Geophysics, Chinese Academy of Sciences.
The Yellowstone region, characterized by a relatively thin crust, serves as a center of intense volcanic activity. Over the last 2.1 million years, Yellowstone has experienced three massive eruptions, the most recent of which occurred 631,000 years ago. This last super-eruption resulted in the formation of the Yellowstone caldera, a depression spanning over 50 kilometers across. A caldera is a bowl-shaped feature that forms on the surface after molten rock from the volcano has erupted out.
The origin of the igneous rocks in Yellowstone National Park has been a long-standing subject of scientific debate. Some researchers postulate that a mantle plume exists beneath the surface. A mantle plume is a column of exceedingly hot rock ascending from the boundary between the Earth’s core and mantle, heating up the crust above. Conversely, others argue that Yellowstone’s volcanism is linked to pressures within the crust and mantle itself.
“Based on these differing hypotheses, we can make projections about how Yellowstone’s volcanic system might operate in the future,” commented Jamie Farrell, Chief Seismologist at the Yellowstone Volcano Observatory, who was not involved in the new study.
In the new research, published in the journal Science, the researchers contend that tectonic processes alone are capable of heating up magma chambers beneath Yellowstone, even without the influence of a deep mantle plume.
They constructed a three-dimensional model that accounted for the movements of tectonic plates in the western part of North America historically, the current subsurface structure beneath Yellowstone, and data pertaining to the lithosphere—Earth’s rigid outer rocky layer.
According to Liu, the team determined that the Yellowstone magma conduits originated from tectonic actions rather than a mantle plume, and that the system is subject to the influence of two opposing forces.
The lithosphere beneath Yellowstone exhibits variable density, meaning some sections are heavier than others. Liu explained that this differential density causes the surface crust to stretch westward toward the US coast, somewhat comparable to stretching dough.
Simultaneously, the older tectonic slab—the Farallon plate—is subducting beneath central and eastern North America, dragging the lower portion of the crust down with it and tilting the volcanic system.
In Yellowstone, these two forces are engaged in a contest. “This competition results in the fracturing of the lithosphere beneath Yellowstone,” Liu noted, adding that the volcanic system connects the surface features of Yellowstone to the layers beneath the crust, drawing magma upward.
Nina L. Bennington, a volcanologist-seismologist at the Hawaiian Volcano Observatory, who did not participate in the research, mentioned that a recent geophysical survey indicated that the magma feeding the Yellowstone complex originates in the southwest section of the complex, within the upper mantle, directly below the lithosphere. From there, the magma travels toward the northeast, situated beneath the crust supporting the Yellowstone caldera. The current research provides an explanation for how the magma might have traversed this specific path.
“To my knowledge, prior to this work, no studies had elucidated why the magma fueling the Yellowstone volcanic system follows precisely this trajectory,” she remarked.
Understanding the mechanics of magma heating will enable scientists to generate more precise forecasts for future activity in the region. “This will allow for a better assessment of what we should anticipate moving forward,” Farrell stated. He added that for the past 17 million years, active volcanism has essentially ‘burned through’ a comparatively warm and thin crust, but relatively soon—in geological terms, at least—these systems will begin to melt through a much colder, harder, and thicker crust located to the east of the current Yellowstone National Park boundaries.
“Depending on the ultimate heat source—whether it’s a mantle plume or tectonic forcing—the resulting scenario could differ significantly,” Farrell commented.
Liu suggested that Yellowstone is not the only volcanic system that could benefit from this type of modeling. It could also be applied to enhance the understanding of the Toba volcano in Southeast Asia, the Taupō volcano in New Zealand, and active volcanoes in northeastern China, he said.
Bennington concurred that the new findings and the accumulated knowledge about Yellowstone could prove beneficial in the study of other volcanic systems. “The same type of analysis could be applied to gain a better grasp of how magma migrates within caldera systems that experience high volcanic output globally,” she concluded.
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