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Author Topic: How long does it take for water to carve rocks?  (Read 2947 times)

Offline thedoc

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How long does it take for water to carve rocks?
« on: 15/07/2012 11:30:01 »
Oscar Noe asked the Naked Scientists:
   
How long does it take for water to carve rocks?

And were rivers bigger in the past than they are today?

What do you think?
« Last Edit: 15/07/2012 11:30:01 by _system »


 

Offline Bass

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Re: How long does it take for water to carve rocks?
« Reply #1 on: 15/07/2012 16:26:21 »
Depends on a lot of factors.
1. How resistant to erosion is the rock?
2. Gradient of the water flow?
3. Volume of water flow?
4. Sediment load of the water (mud, silt, sand, etc in the water)?
5. Is the water flow constant or episodic?
6. Vegetation?

The idea that many of the large canyons (chasms?) once thought created by millions of years of erosion from relatively small rivers/streams is currently being challenged as geologists are finding more evidence for catastrophic floods (sometimes repeated) that could quickly erode far more material.
 

Offline Don_1

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Re: How long does it take for water to carve rocks?
« Reply #2 on: 16/07/2012 14:38:34 »
Depends on a lot of factors.

6. Vegetation?


Would you agree that vegetation can be a factor in two opposing ways?

Roots in soil can help prevent erosion, while roots in bare rock can speed up erosion. Even some seemingly delicate plants can get a foothold in some of the tiniest cracks, then, if in the right situation, could eventually widen cracks by the force of their roots. Small trees and shrubs can be seen growing in the most unlikely places. As they grow, so their roots become bigger and stronger, excerpting more strain on the substrate in which they growing. Over time, this could lead to a large chunk of rock face becoming dislodged and falling away, very probably taking the tree with it. Also, the wind rocking such precariously situated trees could add to the problem.
 

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Re: How long does it take for water to carve rocks?
« Reply #2 on: 16/07/2012 14:38:34 »

 

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