Ancient super-eruptions in Yellowstone Hotspot track 'significantly larger' than expected

March 24, 2016
The entire cliff would have been deposited very quickly from a fast-moving current of hot gas and ash (a pyroclastic density current), and the extreme temperatures (900-1000°C) caused the ash to weld to the ground and effectively enameled the area in dense volcanic glass. Note how the ancient top soil has been baked to orange terracotta in response to the intense heat. Credit: Marc Reichow, University of Leicester

A number of giant super-eruptions between 8 and 12 million years ago that could be larger than the colossal eruptions known to have taken place at Yellowstone have been identified in the United States through research led by the University of Leicester.

The international research team suggests that while the number of thought to have originated from the central Snake River Plain in Idaho, USA is less than previously believed, the 12 recorded giant 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, the University of Copenhagen, Denmark and Idaho State University.

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.

Scenic canyon in southern Idaho, USA, which beautifully exposes several cliff-forming, intensely-welded deposits each recording an individual giant eruption. Credit: Marc Reichow, University of Leicester

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.

Dr Knott said: "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.

"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."

Explore further: Evidence in the Cassia Hills of Idaho reveals 12 catastrophic eruptions

More information: Thomas R. Knott et al. Mid-Miocene record of large-scale Snake River−type explosive volcanism and associated subsidence on the Yellowstone hotspot track: The Cassia Formation of Idaho, USA, Geological Society of America Bulletin (2016). DOI: 10.1130/B31324.1

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Protoplasmix
5 / 5 (6) Mar 24, 2016
When is the next eruption? Last time I checked it was predicted to be between anytime and maybe never.

This makes it sound closer to anytime:
"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.

While this makes it sound closer to maybe never:
"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."


Do the newly discovered super-eruptions have the same periodicity as those previously known? And how uniform is the mantle along the path of the hot spot?
starfart
5 / 5 (6) Mar 26, 2016
Protoplasmix: Over the last 16 million years, estimated ages of major eruptions have been dated to 16.1 million, 13-15 million, 10-12 million, 7-10 million, and 4.3 - 6.4 million years ago, with several of the event spans apparently occurring in separate caldera centers along the track. It isn't clear if these spans indicate protracted eruptive episodes or uncertainty. Naively, if one simply looks at the intervals between the mean values (16.1, 14, 11, 8.5[twice], 5.35 and 2.1 million years) one arrives at an average interval of 2.75 million years. It is perhaps better to consider the last three great eruptions when attempting to arrive at an estimate for the period. They consist of events 2.1 million, 1.2 million and 560,000 years ago. The first two are separated by 900,000 years, and the last two by 640,000 years, so we might expect the current periodicity to be around 700,000 years between the big eruptions. However, smaller ones have occurred-the latest only 70,000 yrs ago
starfart
5 / 5 (6) Mar 26, 2016
Since the last big eruption occurred 560,000 years ago, we are perhaps closer to the next one than we are to the last one. But there is nothing to indicate that the next one is imminent, as so many hype-mongering rags like to scream out in their headlines. The more 'immediate' threat of eruption by Yellowstone is presented by the 'smaller' variety: those are sporadic, less predictable yet more frequent, yet might easily rival a Mount St. Helens or even a Pinatubo, which certainly aren't benign events. But imagine the panic in the public conditioned by irresponsible entertainment-news who fear ANY unusual event, however small, might trigger a great eruption at any moment. That alone could be as costly in lives as the St. Helens. eruption.
Protoplasmix
5 / 5 (4) Mar 26, 2016
Thanks for the knowledgeable, sensible reply. I'm guessing that a successful model for predicting the smaller variety (including earthquakes for areas like Los Angeles) is only possible by first having a model to predict large scale, less frequent, super-events. Or is it analogous to being able to predict short-term weather without necessarily including the long term climate change data?
compose
Mar 26, 2016
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compose
Mar 26, 2016
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chileastro
3 / 5 (4) Mar 26, 2016
compose

1 / 5 (2) 7 hours ago

But there is nothing to indicate that the next one is imminent

I beg to disagree. The Yellowstone caldera is uplifting with increased speed and not only that - it also exhibits lateral motion in similar way, like the fluid above bubble rising - which would indicate, the thickness of crust above magma decreases. The geologically ancient helium-4 formed at large depths gets released, the frequency of microquakes is increasing and so on. In recent years even the asphalt at the Yellowstone roads melts.


And let me guess. Your tinfoil hat has matching booties to deal with it?

I suppose once you deny AGW you've got to have another explanation. Ever noticed how these conspiracy idiots always want gloom and doom? It's a desperate hope that everyone will end up with lives as empty and meaningless as their own.

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