The Yellowstone Super Volcano: “Ancient Eruptions Larger Than Previously Thought”



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Six hundred thousand years ago there was a colossal explosion from a cauldron of magma, the most massive known supervolcano, the 2.2 million acre Yellowstone caldera that forms the world's highest plateau capping a seething magma chamber forty-five miles across-the size of Rhode Island- and eight miles thick of hot molten rock that rises up from 125 miles from the Earth's core. When Yellowstone explodes, and it will again, someday, Hiroshima will look like child's play. What no knows for sure is, when.

The ancient Yellowstone caldera exploded with such violence that it left an ash layer almost ten feet deep a thousand miles away in eastern Nebraska killing all plant life and covering almost all of the United States west of the Mississippi. Modern geological surveys have shown that this supervolcano erupts approximately every 600,000 years. The Blackfoot Indians called it the land of evil spirits -what we call today, Yellowstone National Park.


This week researchers, led by a team from the University of Leicester, reported that a number of giant super-eruptions between 8 and 12 million years ago could be larger than the colossal eruptions known to have taken place at Yellowstone have been identified through research 

The international research team suggests that while the number of volcanic eruptions thought to have originated from the central Snake River Plain in Idaho, USA is less than previously believed, the 12 recorded giant eruptions were likely 'significantly larger' than research has previously suggested.

Dr Tom Knott, Professor Mike Branney and Dr Marc Reichow, from the University of Leicester's Department of Geology's Volcanology Group, conducted the research with a team of international collaborators from the University of California, Santa Cruz, USA, the University of Copenhagen, Denmark and Idaho State University, USA.

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Using a multi-technique approach, including whole-rock and mineral chemistries, palaeomagnetic data, and radio-isotopic dates, the team has been able to 'fingerprint' individual eruption deposits and correlate these over vast regions (e.g., 1000's km2).

In establishing widespread correlations, the team drastically reduced the number of eruptions previously thought to have originated from the central Snake River Plain by more than half.

The researchers have reported that one of the super-eruptions from the Yellowstone hotspot-track, defined as the Castleford Crossing eruption, occurred about 8.1 million years ago and estimate the eruption volume to have exceeded 1,900 km3. The single volcanic sheet covers an area over 14,000 km2 in southern Idaho, and is more than 1.3 km thick in the caldera of the super-volcano.

This is just one of 12 giant eruptions reported from the area by the Leicester team, who show that intense hotspot magmatism caused major crustal subsidence, forming the 100 km-wide Snake River Basin. The team also demonstrates that these eruptions were in fact significantly larger than previously thought and may rival those better known at Yellowstone.

"While it is well-know that Yellowstone has erupted catastrophically in recent times perhaps less widely appreciated is that these were just the latest in a protracted history of numerous catastrophic super-eruptions that have burned a track along the Snake River eastwards from Oregon to Yellowstone from 16 Ma to present," said Knott.

"The size and magnitude of this newly defined eruption is as large, if not larger, than better known eruptions at Yellowstone, and it is just the first in an emerging record of newly discovered super-eruptions during a period of intense magmatic activity between 8 and 12 million years ago."

The Daily Galaxy via University of Leicester

Image credits: U.S.National Park Service, and  thanks to


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