Discovery of Ancient Super-Eruptions Indicates the Yellowstone Hotspot
May Be Waning
Boulder, Colo., USA: 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
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
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.
Discovery of two new super-eruptions from the Yellowstone hotspot track
(USA): Is the Yellowstone hotspot waning?
AUTHORS: Thomas R. Knott; Michael J. Branney; Marc K. Reichow; David R.
Finn; Simon Tapster; Robert S. Coe
CONTACT: Thomas Knott, firstname.lastname@example.org
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