Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rare volcanic plumes create uncommonly dangerous ash flows

16.03.2006


Three unique photographs of a recent volcanic eruption in a remote part of Ecuador show a plume unlike any previously documented, and hint at a newly recognized hazard, say scientists at the University of Illinois at Urbana-Champaign.


Plume of Volcán Reventador



"The usual volcanic plume consists of a stalk capped with an umbrella, and resembles the mushroom of an atom bomb blast," said geology professor Susan Kieffer, "but the umbrella on this plume was wavy, like the shell of a scallop."

In a paper scheduled to appear March 15 in the journal Geophysical Research Letters, Kieffer, theoretical and applied mechanics professor Gustavo Gioia, and graduate student Pinaki Chakraborty explain what might have caused the umbrella to scallop, a task made more difficult by the scarcity of information.


"We had never seen a scalloped umbrella before," said Kieffer, who holds a Charles R. Walgreen Jr. Chair at Illinois. "Unusual conditions must have existed in the volcanic plume that formed this umbrella."

Located about 100 kilometers from Quito, Ecuador, Volcán Reventador -- Spanish for "one that explodes" -- lived up to its name on the morning of Nov. 3, 2002. Following seven hours of seismic activity and billowing steam, the summit cone exploded and sent a stream of ash, called a pyroclastic flow, several kilometers down nearby valleys. While traveling close to the ground, the ash heated the surrounding air, which became buoyant as in a hot-air balloon. The air rose in a volcanic plume, carrying the ash with it.

"A volcanic plume rises until the atmosphere becomes so thin that the mixture of air and ash loses buoyancy and starts to spread laterally, forming an umbrella," Gioia said. "The umbrella spreads and cools for a long time before the ash begins to fall gradually."

But instead of the usual hot ash, the Reventador eruption appears to have been laden with steam and a fairly cool ash from the destruction of the summit cone. The unusually cool umbrella could not spread for a long time. It rapidly became a heavy mixture of air, steam and ash hovering precariously over the lighter air below.

"When a heavier fluid is placed on top of a lighter one, you might say that the fluids want to be reversed," said Chakraborty, the paper’s lead author. "The ensuing tug of war between gravity and the viscosity of the fluids results in a wavy instability that pulls the heavier fluid on a fast sinking course."

In laboratory experiments, the fluids are initially at rest, and the wavelength of the instability is a fraction of an inch. But the mixture of air, steam and ash in the Reventador umbrella was turbulent, with many fast, locally swirling motions.

"Turbulence magnifies the wavelength," Chakraborty said. "It gave the Reventador umbrella its distinctive scallops, which were hundreds of meters in wavelength."

While most umbrellas produce gradual ash falls, scalloped umbrellas behave differently and might represent a previously unrecognized hazard.

"Our analysis suggests that the Reventador umbrella collapsed rapidly, forming new and especially dangerous ash flows," said Kieffer, who is also a professor in the university’s Center for Advanced Study, one of the highest forms of campus recognition.

Originating far from the summit cone, these new ash flows must have helped spread the damage caused by the eruption. They must have been uncommonly energetic, because the ash fell from the umbrella, which was 10 kilometers high.

"For all we know, these flows were responsible for broken petroleum pipelines," Chakraborty said. "The flows might also have contributed to the early phases of a shutdown of Quito airport that lasted more than a week."

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Earth Sciences:

nachricht From volcano's slope, NASA instrument looks sky high and to the future
27.04.2017 | NASA/Goddard Space Flight Center

nachricht Penn researchers quantify the changes that lightning inspires in rock
27.04.2017 | University of Pennsylvania

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

Control of molecular motion by metal-plated 3-D printed plastic pieces

27.04.2017 | Materials Sciences

Move over, Superman! NIST method sees through concrete to detect early-stage corrosion

27.04.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>