NOW THERE ARE 13
Correspondent:: joseywales@outlaw.nospam (David James Polewka)
Date: Wed, 05 Jan 2005 18:24:57 GMT
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Scientists at Columbia University's Lamont-Doherty Earth Observatory
report direct evidence that one of the Earth's great crustal plates is
cracking in two - 1995.
In a report published in the most recent issue of Earth and Planetary
Science Letters (vol. 133), the scientists say they have confirmed that
the Indo-Australian Plate--long identified as a single plate on which
both India and Australia lie--appears to have broken apart just south of
the Equator beneath the Indian Ocean. The break has been underway for
the past several million years, and now the two continents are moving
independently of one another in slightly different directions.
Scientists have known that for some 50 million years, the Indian
subcontinent has been pushing northward into Eurasia, forcefully raising
the Tibetan Plateau and the Himalayan Mountains. The new research
suggests that starting about 8 million years ago, the accumulated mass
became so great that the Indo-Australian Plate buckled and broke under
the stress.
"The result of this critical stage in the collision between India and
Asia is the breakup of the Indo-Australia Plate into separate Indian and
Australian plates," Jeffrey Weissel, a scientist at Lamont-Doherty,
Columbia's earth sciences research institute in Palisades, N.Y., said in
an interview.
"In the Central Indian Ocean, Nature is conducting a large-scale
laboratory experiment for us, showing us what happens to the oceanic
lithosphere (Earth's outer layer) when force is applied," Dr. Weissel
said in an interview. Essentially pushed into an immovable object, "it
can buckle like a piece of tin," he said.
A fundamental tenet of plate tectonics theory is that the Earth's
surface is divided into rigid plates that move together and apart like
pieces of a jigsaw puzzle. Scientists have long recognized 12 major
plates. Now there are 13. In the 1970's, scientists first discovered a
broad zone, stretching more than 600 miles from east to west where the
equatorial Indian Ocean floor was compressed and deformed. Drilled
samples had shown that the zone had begun to buckle and crack about 8
million years ago at the same time that the Tibetan Plateau had reached
its greatest height. Dr. Cochran was chief scientist of the drilling
cruise that collected this data.
More recently, researchers at Northwestern University, led by Richard
Gordon and Seth Stein, used data on how newly created seafloor had
spread outward from mid-ocean ridges to the west and south of the
deformed region in the Indian Ocean. They theorized that the movements
of the newly created seafloor could be accommodated only if a distinct
plate boundary existed between separate Indian and Australian plates
across the equatorial Indian Ocean.
In relation to the Indian plate, the Australian Plate is moving
counterclockwise, the Northwestern University scientists calculated. In
the western part of the new plate boundary, the plates are moving away
from each other. To the east, the Australian Plate is converging on the
Indian Plate, they said. If the theory was correct, the ocean floor in
the eastern part of the new plate boundary should be compressed,
buckled, cracked and eventually thrust upward along the cracks. More
critically, if a separate Australian Plate were rotating
counterclockwise in relation to a separate Indian Plate, the amount of
compression should increase rapidly and systematically from west to east
across the Central Indian Ocean. <>To test the theory, the
Lamont-Doherty team took actual measurements of how compressed the
Indian Ocean floor has become in the region believed to be the new plate
boundary. Using sound waves to probe oceanic rock layers, they created
images of subseafloor structures.
The images were collected during two separate research voyages that each
spanned the entire deformed zone from north to south. Dr. Weissel and
Dr. Jestin were aboard the 1991 "Phedre" cruise of the French research
vessel Marion Dufresne. In 1986, Lamont-Doherty's former research
vessel, the Robert D. Conrad, obtained images along a north-to-south
line 185 miles farther west. <>The images showed scores of
systematically aligned cracks, or faults, in the oceanic
lithosphere--created as the once-whole plate buckled and cracked. As the
now-distinct plates continued to converge, slabs of ocean floor slid
upward along the faults to alleviate the strain. The more the two plates
converged, the farther the slabs slid upward. The measurements clearly
showed that two separate plates were converging. More importantly, the
thrusting observed on the "Phedre" seismic line was about twice that
found along the Conrad's line. That proved that compression was more
intense to the east--confirming the Northwestern group's prediction from
the data on spreading rate and direction at the mid-ocean ridges.
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"Endeavor to persevere"
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Correspondent:: "Dr Apocolyptical"
Date: 5 Jan 2005 12:50:46 -0800
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Is this going to affect my taxes?
Correspondent:: Ljutefisk Geist
Date: Thu, 06 Jan 2005 13:32:36 GMT
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In article <41dc3149.74647106@news.east.earthlink.net>,
joseywales@outlaw.nospam says...
>
> Scientists have known that for some 50 million years, the Indian
Have scientists been around THAT long?
> In the 1970's, scientists first discovered a broad zone, stretching
Where da' wimmen at?