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Author Topic: 40 acre rock was the beach??  (Read 5001 times)

Offline OokieWonderslug

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40 acre rock was the beach??
« on: 10/10/2011 23:33:54 »
I have a geology book I bought that talks about all the interesting places to go in North and South Carolina. In it there is an article on 40 acre rock. This is a site near Pageland, SC that I have been to many times. I found one obvious mistake in the book about the site. That mistake being that they said that the pools on the rock are natural. I know they are not. They start from having a fire on the rock and that causes the rock to weaken and makes a dent in the rock and water can stay there and start the process of erosion. The pools all began as fires set by indians.

But farther along in the article it states that the flatness of the formation is due to wave action from when the ocean was much deeper. It flatly states that 40 acre rock was eroded flat from the action of ocean waves.

If that is true, then there has been no significant erosion there for 65 million years. The sand is all beach sand and not wind deposits. The area was not buried and re exposed. And previous threads about the origin of Sugarloaf mountain are not correct.

So is the book wrong? Why would they say that it was made flat by the ocean and not by what ever stopped this mass of granite from ever reaching the surface? I would think that what ever mass was dense enough to halt the upwelling of 30 square miles of molten granite would have lent a small amount to it's final shape when it solidified.

Clarification?


 

Offline OokieWonderslug

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40 acre rock was the beach??
« Reply #1 on: 25/10/2011 23:12:03 »
No one? No one can explain how the ocean was in Pageland, SC 65,000,000 years ago and yet somehow magically the net deposition/erosion equals zero at that site? Well, not zero since the area is now about 300ft above sea level, but darn close.
 

Offline Airthumbs

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40 acre rock was the beach??
« Reply #2 on: 26/10/2011 00:55:32 »
You already have the key to the solution in your knowledge of the formation of this once molten lava pipe.  The very composition of this rock makes it more resistant to erosion then the earth it was forced through when it formed.  It may not have reached the surface due to lack of pressure and the link supplying it was severed deep in the mantle of the planet.  On how deep the pipe goes and what the structure beneath the surface is like would need some kind of geological survey.  Over Eons the surrounding soil has been eroded away from the pipe leaving it standing above the now lower ground around it.  It will continue to "grow" in height until one day it will be a truly spectacular structure.

Any deposition on the surface of the granite outcrop from the ocean would have been eroded away after the ocean moved elsewhere but the more powerful erosive forces of the ocean may have shaped and smoothed the structure.  I have never seen it so I don't know what it looks like. 

If this place is one of those spots where you find shells in the sand sometimes then that's one type of evidence for an ancient ocean.  Have you been there?

You may also consider that depending on how old this ocean was the formation of this structure may have taken place beneath the ocean.   
 

Offline OokieWonderslug

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40 acre rock was the beach??
« Reply #3 on: 26/10/2011 02:43:29 »
No, that is not what it is like. It is a feature that is lower than the surrounding land, but not by much. It was a huge mass of igneous rock that cooled far below the surface some 200,000,000 years ago. Erosion has brought it to the surface. North and West of 40 acre rock the land is higher and has slightly more relief than the area South and East which is lower. It is pretty much what you'd expect an ancient beach to be minus any evidence of any kind of fossil life. There is obvious erosion of what would have been flat land when the ocean was there. But zero evidence of anything recovering it and then eroding away again.

Yes I have been there hundreds of times.
 

Offline CliffordK

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40 acre rock was the beach??
« Reply #4 on: 26/10/2011 04:11:39 »


It doesn't appear to be very close to the current beach.  Certainly elevations have changed over time, and the ocean has risen and fallen.  And, there have been uplifting events of the crust.

I believe the Appalachian Mountains are supposed to be a very old chain of mountains with significant erosion.  Unlike Lava, Granite is always formed deep below the surface, but in many cases, it is pushed up to the surface forming hills and mountains. 

As far as the surface irregularities of the rock, some may be due to campfires.  But, I would imagine many of them are just natural.  Nothing that big in nature is perfectly flat, and small imperfections are places where plant life can take hold, and water can collect and freeze, thus making larger imperfections.  Or, if one is talking about waves, small imperfections could amplify wave actions, and also collect materials on the beach.

One question that I would have.  I'm trying to imagine the ocean shores that I've been on, and don't remember any 40 acre (or 15 acre) solid granite beaches.  I've been on rocky shores, but none are flat.  At least not flat and horizontal.  I think Dover was flat and vertical.  Maybe some have had a bit of a shelf above the ocean.  But, again not smooth and flat.  So, I would ask for an example where a similar ocean erosion is happening.  Keeping in mind, of course, that our current shorelines are only about 10,000 years old.

Perhaps beach isn't the way to think of it.  While I don't dive, I've seen photos of flat subsurface rocks in the ocean and seas. 

I'm trying to remember other flat rocky outcroppings.  Lots of flat rocks.  Perhaps that reminds me a bit of Southern Italy.

 

Offline OokieWonderslug

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40 acre rock was the beach??
« Reply #5 on: 01/11/2011 04:54:16 »
Here is some flat rock beach. Is this what extreme northern South Carolina looked like 65,000,000 years ago?

http://0.tqn.com/d/geology/1/0/N/O/1/platdavenport.jpg
 

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40 acre rock was the beach??
« Reply #5 on: 01/11/2011 04:54:16 »

 

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