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Author Topic: How do we know what is in the center of the earth? How far has a human been down  (Read 8791 times)

Offline Simulated

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How do we know what is further down then what a human has been? How far have we been down towards the center? What's the furthest things we've sent down?

Thanks Sim  :)


 

Offline Bass

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The Kola Superdeep Borehole, located in western Russia, is the deepest hole ever drilled- over 40,000 feet.  The ultimate goal, to reach the Moho, was never achieved.
The rocks encountered literally trashed some long-held geologic assumptions based on seismic profiles.  For example, instead of drilling into expected basalt in the lower crust (at a particular seismic discontinuity found in continental crustal rocks), the drill hole encountered metamorphic rocks full of water- which according to hypotheses, couldn't exist at those temperatures/prssures.
So your point is well taken, we won't actually know what's down there until we can somehow manage to actually sample the rocks.  The theories on the deep earth's composition are all based on indirect evidence, such as seismic patterns, the magnetic fields, the mass of the earth, rocks exposed at the surface that were thought to be part of the mantle at one time, and meteorite fragmaents.  The existing theories tie all these bits of indirect evidence together, but certainly other possibilities exist.
 

Offline Simulated

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Thanks, but what is the Moho?
 

Offline frethack

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Bass, have you read the article about a University of Houston researcher that retrieved 2 billion year old samples from the North Atlantic that seem to argue against a comepletely homogeneous mantle?  I know VERY little about this, but Ill post the article.  Maybe you and JimBob can enlighten us.

Here is the UofH press release

http://www.uh.edu/news-events/newsrelease.php?releaseid_int=190

 
 

Offline Bass

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Sim
The Moho is short for the Mohorovičić discontinuity (now you see why we just call it the Moho), shown by a change in seismic waves that is the boundary between the crust and mantle.
 

Offline Bass

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Have not read the article, however have seen several papers on heterogeneous mantle- will try to dig some up.
 

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