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Author Topic: Why is Earth's mantle more complex than previously thought?  (Read 5748 times)

Offline Bass

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Two billion year old rocks recovered from the Arctic seafloor suggest the mantle may be more complex and heterogeneous than previously thought.  Jonathan Snow (appropriate name for an Arctic researcher), University of Houston assistant professor of geosciences, collected the rocks along the  Gakkel Ridge in the Arctic Ocean between Greenland and Siberia.  The rocks were dated using osmium isotopes.
http://www.uh.edu/news-events/newsrelease.php?releaseid_int=190
« Last Edit: 15/04/2008 09:17:15 by chris »


 

Offline DoctorBeaver

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So rocks in this area mix 10 times slower than elsewhere? Does anyone know why that is? Why is there such little tectonic movement there?
 

Offline Exodus

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It couldn't have anything to do with the earth's magnetic field could it? I am very poor on my hard rock stuff so don't mock me.
 

Offline Bass

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Gakkel Ridge is the northern terminus of the Mid Atlantic Ridge, and one of the slowest spreading mid oceanic ridges (less than 1 cm/year).  At present, there are no subduction zones on either side of the ridge.
 

Offline JimBob

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There is still the question of the origin, if any,of iron concentration in the core to be answered. It is therefor logical that if iron differentiation (and other elements) are not as zonated as once thought that the mantle would reflect this lack of heterogeneity.

As I have access to Nature through my library privileges at the UT library I'll try to look it up tomorrow and see if I can get some more info.
 

Offline DoctorBeaver

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There is still the question of the origin, if any,of iron concentration in the core to be answered. It is therefor logical that if iron differentiation (and other elements) are not as zonated as once thought that the mantle would reflect this lack of heterogeneity.

Just what I was thinking  :P
 

Offline JimBob

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LexisNexis doesn't have Nature online - so I am out for getting the article today - too much work to do. But I did find this article and the note below it.

------------------------------------------------

Christian Science Monitor

April 19, 2007, Thursday

News briefs from the frontiers of science

BYLINE: Peter N. Spotts Staff writer of The Christian Science Monitor

SECTION: FEATURES, CURRENTS; Pg. 17

LENGTH: 696 words

Ocean ridges need to vent

Undersea ridges, where Earth's crust spreads and renews itself, are hot spots for marine biologists and geologists alike. Now, Chinese and US researchers exploring the bottom of the southwest Indian Ocean say they have discovered a large field of hydrothermal vents along an ultra-slow spreading ridge, a type of ridge long thought to be too cool to host them.

Hints that this type of ridge could be a geological and biological hothouse first came from the Gakkel Ridge in the Arctic Ocean, the slowest-spreading ridge on the planet. During a 2001 expedition aboard the US Coast Guard icebreaker Healy, researchers found nine vents, twice as many as theories predicted.

The Indian Ocean team, which included scientists from the Woods Hole (Mass.) Oceanographic Institution, gathered the data in February and March during a Chinese-led expedition aboard the country's research vessel Dayang 1. Sensors aboard robotic undersea vehicles detected plumes of the hot, mineral-laden water the vents spew, and the team used sonar to map the extent of the vent field, which covers an area somewhat larger than a football field. The vent site is one of the largest yet discovered, the scientists say.

(c) Copyright 2007. The Christian Science Monitor


--------------------------------------------

Electronics Weekly

July 4, 2007

BYLINE: Sb

SECTION: TECHNOLOGY

LENGTH: 319 words

Massachusetts-based Woods Hole Oceanographic Institution has created a pair of autonomous robots to explore hydrothermal vents under the arctic ice "Most of the instrumentation that researchers would normally use to study deep sea environments and organisms, such as the human occupied submersibles or tethered vehicles, cannot be safely operated in the Arctic ice which can easily crush most small vehicles," said Wood's Hole. Both robots use a twin hull design with a heavy hull suspended beneath a light one to give vertical stability. 'Puma' detects the plumes that emerge from hydrothermal vents using sensors including sonars, thermometers, chemical sensors, and green lasers to detect particulates which give hydrothermal vent plumes their turbidity.

It then tracks them back to the sea floor vent. 'Jaguar' is designed to fly direct to the discovered vent and hover with camera, lighting and high-resolution bottom-mapping sonar, as well as a manipulator arm for close-up imaging, mapping, and sampling. After 10 to 24 hour missions to the ridge, which is 3 to 5km down, the submarines return by homing in to an acoustic beacon and latching onto a wire suspended from a hole in the ice. "Anyone can deploy an autonomous vehicle in the Arctic, the trick is getting it back," said vehicle developer Hanumant Singh. "In order to have a good day with autonomous vehicles, the number of recoveries must equal the number of launches." Activity in the research area, an extension of the mid-Atlantic ridge called the Gakkel Ridge, begins this week following vehicle trials in May and June. Wood's Hole likens Gakkel to Australia where animals evolved separately for millions of years. "We hope to discover exotic seafloor life and submarine hot springs in a region of the ocean that has been mostly cut off from other ecosystems for at least 26 million years," said the institution.

 
« Last Edit: 12/04/2008 18:02:35 by JimBob »
 

Offline JimBob

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SO - no data here. Need more info.

 

Offline DoctorBeaver

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SO - no data here. Need more info.



Sorry, but that reminds me of the film Short Circuit - "Need more input!"
 

Offline JimBob

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By Jove! You caught the reference, sir. Too bad there is nothing to win.
 

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