Discovery of ancient super-eruptions indicates the Yellowstone hotspot
may be waning

Date:
June 3, 2020
Source:
Geological Society of America
Summary:
Researchers report two newly identified super-eruptions associated
with the Yellowstone hotspot track, including what they believe
was the volcanic province's largest and most cataclysmic event. The
results indicate the hotspot, which today fuels the famous geysers,
mudpots, and fumaroles in Yellowstone National Park, may be waning
in intensity.



FULL STORY ========================================================================== [Grand Prismatic Spring | Credit: (c) gottsfam / stock.adobe.com] Grand Prismatic Spring in Yellowstone National Park (stock image).

Credit: (c) gottsfam / stock.adobe.com [Grand Prismatic Spring | Credit:
(c) gottsfam / stock.adobe.com] Grand Prismatic Spring in Yellowstone
National Park (stock image).

Credit: (c) gottsfam / stock.adobe.com Close Throughout Earth's long
history, volcanic super-eruptions have been some of the most extreme
events ever to affect our planet's rugged surface. Surprisingly, even
though these explosions eject enormous volumes of material -- at least
1,000 times more than the 1980 eruption of Mount St. Helens -- and have
the potential to alter the planet's climate, relatively few have been documented in the geologic record.


==========================================================================
Now, in a study published in Geology, researchers have announced the
discovery of two newly identified super-eruptions associated with the Yellowstone hotspot track, including what they believe was the volcanic province's largest and most cataclysmic event. The results indicate the hotspot, which today fuels the famous geysers, mudpots, and fumaroles
in Yellowstone National Park, may be waning in intensity.

The team used a combination of techniques, including bulk chemistry,
magnetic data, and radio-isotopic dates, to correlate volcanic deposits scattered across tens of thousands of square kilometers. "We discovered
that deposits previously believed to belong to multiple, smaller eruptions
were in fact colossal sheets of volcanic material from two previously
unknown super-eruptions at about 9.0 and 8.7 million years ago," says
Thomas Knott, a volcanologist at the University of Leicester and the
paper's lead author.

"The younger of the two, the Grey's Landing super-eruption, is now
the largest recorded event of the entire Snake-River-Yellowstone
volcanic province," says Knott. Based on the most recent collations of super-eruption sizes, he adds, "It is one of the top five eruptions
of all time." The team, which also includes researchers from the
British Geological Survey and the University of California, Santa Cruz, estimates the Grey's Landing super-eruption was 30% larger than the
previous record-holder (the well-known Huckleberry Ridge Tuff) and
had devastating local and global effects. "The Grey's Landing eruption enamelled an area the size of New Jersey in searing-hot volcanic glass
that instantly sterilized the land surface," says Knott.

Anything located within this region, he says, would have been buried
and most likely vaporized during the eruption. "Particulates would have
choked the stratosphere," adds Knott, "raining fine ash over the entire
United States and gradually encompassing the globe." Both of the newly discovered super-eruptions occurred during the Miocene, the interval
of geologic time spanning 23-5.3 million years ago. "These two new
eruptions bring the total number of recorded Miocene super-eruptions at
the Yellowstone-Snake River volcanic province to six," says Knott. This
means that the recurrence rate of Yellowstone hotspot super-eruptions
during the Miocene was, on average, once every 500,000 years.

By comparison, Knott says, two super-eruptions have -- so far --
taken place in what is now Yellowstone National Park during the
past three million years. "It therefore seems that the Yellowstone
hotspot has experienced a three-fold decrease in its capacity to produce super-eruption events," says Knott. "This is a very significant decline."
These findings, says Knott, have little bearing on assessing the risk
of another super-eruption occurring today in Yellowstone. "We have
demonstrated that the recurrence rate of Yellowstone super-eruptions
appears to be once every 1.5 million years," he says. "The last
super-eruption there was 630,000 years ago, suggesting we may have up to 900,000 years before another eruption of this scale occurs." But this
estimate, Knott hastens to add, is far from exact, and he emphasizes
that continuous monitoring in the region, which is being conducted by
the U.S. Geological Survey, "is a must" and that warnings of any uptick
in activity would be issued well in advance.

This study, which builds on decades of contributions by many other
researchers, grew out of a larger project investigating the productivity
of major continental volcanic provinces. Those with super-eruptions are
the result of colossal degrees of crustal melting over prolonged periods
of time, says Knott, and therefore have a profound impact on the structure
and composition of Earth's crust in the regions where they occur.

Because studying these provinces is vital to understanding their role
in shaping our planet's crustal processes, Knott hopes this research foreshadows even more revelations. "We hope the methods and findings we
present in our paper will enable the discovery of more new super-eruption records around the globe," he says.


========================================================================== Story Source: Materials provided by Geological_Society_of_America. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Robert S. Coe, Simon Tapster, David R. Finn, Marc K. Reichow,
Michael J.

Branney, Thomas R. Knott. Discovery of two new super-eruptions
from the Yellowstone hotspot track (USA): Is the Yellowstone
hotspot waning? Geology, 2020; DOI: 10.1130/G47384.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200603132516.htm https://www.sciencedaily.com/releases/2020/06/200603132516.htm

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