Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How rivers of hot ash and gas move when a supervolcano erupts

07.03.2016

Study suggests that pyroclastic flows traveled in dense, slow-moving currents during one ancient supereruption

Supervolcanoes capable of unleashing hundreds of times the amount of magma that was expelled during the Mount St. Helens eruption of 1980 are found in populated areas around the world, including the western United States.


Photographs scanned from Kodachrome slides show dark rocks embedded in layers of ash. The rocks were picked up and moved across the landscape by pyroclastic flows when the Silver Creek caldera, a supervolcano, erupted 18.8 million years ago.

Credit: Greg A. Valentine

A new study is providing insight into what may happen when one of these colossal entities explodes.

The research focuses on the Silver Creek caldera, which sits at the intersection of California, Nevada and Arizona. When this supervolcano erupted 18.8 million years ago, it flooded parts of all three states with river-like currents of hot ash and gas called pyroclastic flows. These tides of volcanic material traveled for huge distances -- more than 100 miles.

The new study suggests that pyroclastic flows from the ancient eruption took the form of slow, dense currents -- and not fast-moving jets as some experts previously thought.

The research combines recent laboratory experiments with field data from the 1980s -- some of it captured in colorful Kodachrome slides -- to show that the rivers of ash and gas emanating from the Silver Creek caldera likely traveled at modest speeds of about 10 to 45 miles per hour.

"Intuitively, most of us would think that for the pyroclastic flow to go such an extreme distance, it would have to start off with a very high speed," says study co-author Olivier Roche. "But this isn't consistent with what we found."

The research was conducted by Roche at Blaise Pascal University in France, David C. Buesch at the United States Geological Survey and Greg A. Valentine at the University at Buffalo. It will be published on Monday, March 7 in Nature Communications, and all information in this press release is embargoed until 5 a.m. U.S. Eastern Standard Time on that date.

Research on pyroclastic flows is important because it can help inform disaster preparedness efforts, says Valentine, a UB professor of geology and director of the Center for GeoHazards Studies in the UB College of Arts and Sciences.

"We want to understand these pyroclastic flows so we can do a good job of forecasting the behavior of these flows when a volcano erupts," he says. "The character and speed of the flows will affect how much time you might have to get out of the way, although the only truly safe thing to do is to evacuate before a flow starts."

New and vintage data come together to tell the story of a supervolcano

The new study favors one of two competing theories about how pyroclastic flows are able to cover long distances. One school of thought says the flows should resemble turbulent, hot, fast-moving sandstorms, made up mostly of gas, with few particles. The other theory states that the flows should be dense and fluid-like, with pressurized gas between ash particles. The new research supports this latter model, which requires sustained emissions from volcanoes, for many pyroclastic flows.

The findings were based on two sets of data: results from recent experiments that Roche ran to simulate the behavior of pyroclastic flows, and information that Buesch and Valentine gathered at the Silver Creek Caldera eruption site in the 1980s when they were PhD students at the University of California, Santa Barbara, supplemented by some more recent fieldwork.

"I always tell students that they should take good notes while they're working in the field, because you never know when it could be useful," says Valentine, who has a fat binder full of Kodachrome slides showing images he snapped around the Silver Creek caldera.

The data that he and Buesch collected included photographs and notes documenting the size, type and location of rocks that were lifted off the ground and moved short distances by pyroclastic flows during the ancient eruption.

Many of the rocks the pair observed were relatively large -- too large to have been shifted by sandstorm-like pyroclastic flows, which do not pick up heavy objects easily. Denser flows, which can move sizable rocks more readily, likely accounted for the rock patterns Buesch and Valentine observed.

To figure out how fast these dense flows may have been moving when the Silver Creek caldera erupted 18.8 million years ago, the team relied on a model developed by Roche through experiments.

In his tests, Roche studied what happened when a gas and particle mixture resembling a dense pyroclastic flow traveled across a substrate of beads. He found that faster flows were able to lift and move heavier beads, and that there was a relationship between the velocity of a flow and the weight of the bead it was capable of lifting.

Based on Roche's model, the scientists determined that the ancient pyroclastic flows from the supervolcano would have had to travel at speeds of about 5 to 20 meters per second (10 to 45 miles per hour) to pick up rocks as heavy as the ones that Buesch and Valentine saw. It's unlikely that the flows were going much faster than that because larger rocks on the landscape remained undisturbed, Valentine says.

The findings could have widespread applicability when it comes to supereruptions, says Valentine, who notes that patterns of rock deposits around some other supervolcanoes heavily resemble those around the Silver Creek caldera.

Media Contact

Charlotte Hsu
chsu22@buffalo.edu
716-645-4655

 @UBNewsSource

http://www.buffalo.edu 

Charlotte Hsu | EurekAlert!

More articles from Earth Sciences:

nachricht Multi-year submarine-canyon study challenges textbook theories about turbidity currents
12.12.2017 | Monterey Bay Aquarium Research Institute

nachricht How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas
11.12.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Long-lived storage of a photonic qubit for worldwide teleportation

12.12.2017 | Physics and Astronomy

Multi-year submarine-canyon study challenges textbook theories about turbidity currents

12.12.2017 | Earth Sciences

Electromagnetic water cloak eliminates drag and wake

12.12.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>