Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. 24/7 Space News .




TECTONICS
Beneath Earth's surface, scientists find long 'fingers' of heat
by Staff Writers
College Park, MD (SPX) Sep 11, 2013


File image.

Scientists seeking to understand the forces at work beneath the surface of the Earth have used seismic waves to detect previously unknown "fingers" of heat, some of them thousands of miles long, in Earth's upper mantle. Their discovery, published in Science Express, helps explain the "hotspot volcanoes" that give birth to island chains such as Hawai'i and Tahiti.

Many volcanoes arise at collision zones between the tectonic plates, but hotspot volcanoes form in the middle of the plates. Geologists have hypothesized that upwellings of hot, buoyant rock rise as plumes from deep within Earth's mantle - the layer between the crust and the core that makes up most of Earth's volume - and supply the heat that feeds these mid-plate volcanoes.

But some hotspot volcano chains are not easily explained by this simple model, a fact which suggests there are more complex interactions between these hot plumes and the upper mantle. Now, a computer modeling approach, developed by University of Maryland seismologist Vedran Lekic and colleagues at the University of California Berkeley, has produced new seismic wave imagery which reveals that the rising plumes are, in fact, influenced by a pattern of finger-like structures carrying heat deep beneath Earth's oceanic plates.

Seismic waves are waves of energy produced by earthquakes, explosions and volcanic eruptions, which can travel long distances below Earth's surface. As they travel through layers of different density and elasticity, their shape changes. A global network of seismographs records these changing waveforms. By comparing the waveforms from hundreds of earthquakes recorded at locations around the world, scientists can make inferences about the structures through which the seismic waves have traveled.

The process, known as seismic tomography, works in much the same way that CT scans (computed tomography) reveal structures hidden beneath the surface of the human body. But since we know much less about the structures below Earth's surface, seismic tomography isn't easy to interpret. "The Earth's crust varies a lot, and being able to represent that variation is difficult, much less the structure deeper below" said Lekic, an assistant professor of geology at the College Park campus.

Until recently, analyses like the one in the study would have taken up to 19 years of computer time. While studying for his doctorate with the study's senior author, UC Berkeley Prof. Barbara Romanowicz, Lekic developed a method to more accurately model waveform data while still keeping computer time manageable, which resulted in higher-resolution images of the interaction between the layers of Earth's mantle.

By refining this method, a research team led by UC Berkeley graduate student Scott French found finger-like channels of low-speed seismic waves flowing about 120 to 220 miles below the sea floor, and stretching out in bands about 700 miles wide and 1,400 miles apart.

The researchers also discovered a subtle but important difference in speed: at this depth, seismic waves typically travel about 2.5 to 3 miles per second, but the average seismic velocity in the channels was 4 percent slower. Because higher temperatures slow down seismic waves, the researchers infer that the channels are hotter than the surrounding material.

"We estimate that the slowdown we're seeing could represent a temperature increase of up to 200 degrees Celsius," or about 390 degrees Fahrenheit, said French, the study's study lead author. At these depths, absolute temperatures in the mantle are about 1,300 degrees Celsius, or 2,400 degrees Fahrenheit, the researchers said.

Geophysicists have long theorized that channels akin to those revealed in the computer model exist, and are interacting with the plumes in Earth's mantle that feed hotspot volcanoes. But the new images reveal for the first time the extent, depth and shape of these channels. And they also show that the fingers align with the motion of the overlying tectonic plate. The researchers hypothesize that these channels may be interacting in complex ways with both the tectonic plates above them and the hot plumes rising from below.

"This global pattern of finger-like structures that we're seeing, which has not been documented before, appears to reflect interactions between the upwelling plumes and the motion of the overlying plates," Lekic said. "The deflection of the plumes into these finger-like channels represents an intermediate scale of convection in the mantle, between the large-scale circulation that drives plate motions and the smaller scale plumes, which we are now starting to image."

"The exact nature of those interactions will need further study," said French, "but we now have a clearer picture that can help us understand the 'plumbing' of Earth's mantle responsible for hotspot volcano islands like Tahiti, Reunion and Samoa."

.


Related Links
Berkeley Seismological Laboratory
University of Maryland
Tectonic Science and News






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





TECTONICS
Seismic finding could explain creation of Earth's 'hot spot' volcanoes
Berkeley, Calif. (UPI) Sep 5, 2013
U.S. scientists say they've made a discovery that helps explain Earth's "hot spot volcanoes" that give birth to island chains such as Hawaii and Tahiti. Unlike volcanoes that emerge at collision zones between tectonic plates, hot spot volcanoes form in the middle of the plates. Most current theories assume a single upwelling of hot, buoyant rock rises vertically as a plume from d ... read more


TECTONICS
Sixteen Tons of Moondust

Scientists say water on moon may have originated on Earth

Moon landing mission to use "secret weapons"

NASA launches spacecraft to study Moon atmosphere

TECTONICS
Explosive flooding said responsible for distinctive Mars terrain

Upgrade to Mars rovers could aid discovery on more distant worlds

Investigating 'Coal Island' Rock Outcrop

Terramechanics research aims to keep Mars rovers rolling

TECTONICS
NASA Spacecraft Embarks on Historic Journey Into Interstellar Space

Elite Group of Young Scientists Embark on DARPA Research Efforts

From Elvis to E.T.? The Voyagers' extraordinary tale

Astronauts prepare for deep space -- by going deep underground

TECTONICS
China civilian technology satellites put into use

China to launch lunar lander by end of year: media

China launches three experimental satellites

Medical quarantine over for Shenzhou-10 astronauts

TECTONICS
ISS Releases a White Stork and Awaits a Swan

Three astronauts back on Earth from ISS: mission control

ISS Crew Completes Spacewalk Preps

Russian cosmonaut set for space station mission resigns

TECTONICS
Arianespace remains the global launch services leader

Russian space official denies report of problem in Soyuz return

Lockheed Martin Atlas V To Launch Morelos-3 ComSat

Japan sets new date for satellite rocket launch

TECTONICS
ESA selects SSTL to design Exoplanet satellite mission

Coldest Brown Dwarfs Blur Lines between Stars and Planets

NASA-funded Program Helps Amateur Astronomers Detect Alien Worlds

Observations strongly suggest distant super-Earth has water atmosphere

TECTONICS
Butterfly wings inspire new technologies: from fabrics and cosmetics to sensors

Calculating the carbon footprint of California's products

First laser-like X-ray light from a solid

Space's 'Ferrari' set to fall to Earth




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