Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




SHAKE AND BLOW
How pre-eruption collisions affect what exits a volcano
by Staff Writers
Atlanta GA (SPX) Jul 26, 2012


Mt. St. Helens pumice.

How much ash will be injected into the atmosphere during Earth's next volcanic eruption? Recent eruptions have demonstrated our continued vulnerability to ash dispersal, which can disrupt the aviation industry and cause billions of dollars in economic loss. Scientists widely believe that volcanic particle size is determined by the initial fragmentation process, when bubbly magma deep in the volcano changes into gas-particle flows.

But new Georgia Tech research indicates a more dynamic process where the amount and size of volcanic ash actually depend on what happens afterward, as the particles race toward the surface.

Their initial size and source depth, as well as the collisions they endure within the conduit, are the differences between palm-sized pumice that hit the ground and dense ash plumes that jet into the atmosphere and can halt aviation.

Assistant Professor Josef Dufek used lab experiments and computer simulations to study particle break-up, known as granular disruption, in volcanic eruptions.

His team, which included the University of California, Berkeley's Michael Manga and Ameeta Patel, determined that shallow (approximately 500 meters below the surface) fragmentation levels likely cause abundant, large pumice that are often seen in large volcanic eruptions.

If the fragmentation begins a few kilometers underground, the volcano is more likely to emit fine-grained ash.

"The longer these particles stay in the conduit, the more often they collide with each other," said Dufek, a faculty member in Georgia Tech's School of Earth and Atmospheric Sciences.

"These high-energy collisions break the volcanic particles into fractions of their original size. That's why deeper fragmentations produce small particles. Particles that begin closer to the surface with less energy don't have time for as many collisions before they exit the volcano. They stay more intact, are larger and often contained in pyroclastic flows."

The team collected volcanic rock from California's Medicine Lake volcanic deposit for collision experiments. They also used glass spheres because, like glass, pumice is heated and hardens before crystals are able to form.

Using a pumice gun that propels volcanic fragments using compressed gases, Dufek and his team determined that particles must collide at a minimum of 30 meters per second to break into larger pieces.

Using numerical simulations, the researchers concluded that large pumice particles (greater than fist size) will not likely remain intact unless the fragmentation is very shallow. Abundant large pumice rocks in a deposit provide an indication of the depth of fragmentation, which may vary over the course of the eruption.

Due to the depth and violent nature of the process, scientists have had little record of the depth of the fragmentation process, even though much of the eruptive dynamics and subsequent hazards are determined in this process.

Dufek and his team will next use the research to better understand the dynamics of one of the most rare natural disasters: super volcanoes, which produced the features in Yellowstone National Park.

"We know very little about the eruption processes during super eruptions," said Dufek. "Indications of their fragmentation levels will provide important clues to their eruptive dynamics, allowing us to study them in new ways."

The findings are published in the current edition of Nature Geoscience.

.


Related Links
Josef Dufek's Website
Bringing Order To A World Of Disasters
When the Earth Quakes
A world of storm and tempest






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





SHAKE AND BLOW
X-rays illuminate the origin of volcanic hotspots
Paris, France (SPX) Jul 19, 2012
Scientists have recreated the extreme conditions at the boundary between Earth's core and its mantle, 2,900 km beneath the surface. Using the world's most brilliant beam of X-rays, they probed speck-sized samples of rock at very high temperature and pressure to show for the first time that partially molten rock under these conditions is buoyant and should segregate towards the Earth's surface. ... read more


SHAKE AND BLOW
Disaster-hit Japan could use microfinance: Yunus

In Haiti, anger over slum eviction plans

Japan probes claim workers' radiation levels faked

Japan sets compensation for Fukushima evacuees

SHAKE AND BLOW
Google unveils ultrafast wired home project

Stone Age tools help to streamline modern manufacturing

Headwall's Hyperspectral Sensors Set to Lift Off with NT Space

Cassidian announces passive radar system

SHAKE AND BLOW
'Red tide' species is deadlier than first thought

Scientists confirm existence of vitamin 'deserts' in the ocean

Egyptian navy seizes five Italian trawlers: reports

Ancient Alteration of Seawater Chemistry Linked With Past Climate Change

SHAKE AND BLOW
Scientists find Grand Canyon-sized rift under Antarctic ice

Tropical plankton invade Arctic waters

Satellites see Unprecedented Greenland Ice Sheet Melt

Polar bear evolution tracked climate change

SHAKE AND BLOW
Mexico to vaccinate 10 million birds in flu outbreak

Super Bags to thwart rice wastage now available to Filipino farmers

Evolution highly predictable for insects eating toxic plants

Lighting up the plant hormone 'command system'

SHAKE AND BLOW
Croscat Volcano may have been the last volcanic eruption in Spain 13,000 years ago

How pre-eruption collisions affect what exits a volcano

Beijing floods caused 'significant losses': official

6.4-magnitude quake hits Indonesia's Sumatra: USGS

SHAKE AND BLOW
Panetta to visit North Africa, Middle East

Brother of exiled Rwandan ex-army chief gets 9 years' jail

Mozambique told to tackle crime

New sapphire find sends panners into Madagascar lemur park

SHAKE AND BLOW
Japan women lose longest-lived title: government

Kissenger: virtual lips for long-distance lovers

Oregon's Paisley Caves as old as Clovis sites - but not Clovis

Unique Neandertal arm morphology due to scraping, not spearing




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement