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#...madagaskar stone forest - 1 день осени

Feb. 24th, 2010

09:06 pm - #...madagaskar stone forest

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From:(Anonymous)
Date:February 28th, 2010 03:01 pm (UTC)

HOW

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a couple of you asked how this happened.. well, after studying geology, the only thing i can think of that would cause this to happen is that the base ground level used to be approximately where the tops of these outcroppings are. while the ground was at said level, molten rock came up through the ground [theyre called "dikes"] and created the rock formations you see here. these rocks are strong, while the dirt around them was not. over what im sure was several hundred years, the dirt around these dikes eroded away, leaving the dikes exposed!
:D
-SAF
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From:(Anonymous)
Date:February 28th, 2010 09:37 pm (UTC)

Re: HOW

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wow! thank you for your explanation. what a wonderful world we live in.
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From:(Anonymous)
Date:April 28th, 2010 04:16 pm (UTC)

Re: HOW

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soooo...you're saying dikes did this?
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From:(Anonymous)
Date:May 1st, 2010 03:49 am (UTC)

Re: HOW

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Good guess, definitely not correct though. I'm also a geologist, and while I know nothing of the specifics, these rocks are clearly limestone. This area must have been a shallow water marine basin at some point. Is it on the African side of Madagascar? My guess is that its associated with the rifting of East Africa. When Madagascar broke away from the continent, a shallow sea formed, marine sediments and biogenic carbonate would have been deposited in the basin and subsequently lithified (turned to stone after sufficient burial).
This type of rock is subject to chemical weathering, especially in the presence of rain water with high levels of carbonic acid (related to CO2 in the atmosphere). The amazing large scale formations you see are canyons formed by channelized water flow throughout the terrain, but the small scale feature of the rock (the sharp edges, and the rounded depressions)are just formed over time, thousands of years, not hundreds, by rain droplets hitting the rock (edges) and collecting in pools (depressions).
If you notice that both on a large and small scale, everything occurs in bands and layers. Those represent individual layers of sediment that were deposited in one event, with the boundaries between layers representing periods of erosion. The little bands probably represent a few tens of years of deposition each, whereas the stratification of the canyons represent a many thousands to a few million years of deposition.
How's that for an explanation!?
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From:(Anonymous)
Date:May 27th, 2010 06:21 am (UTC)

Re: HOW

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I'm pretty sure it's an extreme case of rillenkarren formations.
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From:(Anonymous)
Date:May 28th, 2010 04:48 am (UTC)

Re: HOW

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Really god explanation, excellent photos. Thanks all!
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From:(Anonymous)
Date:May 28th, 2010 08:41 pm (UTC)

Re: HOW

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I think you'll find God did it...
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From:(Anonymous)
Date:July 3rd, 2010 08:27 am (UTC)

Re: HOW

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Funny that killed this thread! God? Don't make me laugh...lol... too late.

On another note, thanks for the explanations, I believe the limestone erosion theory is the correct answer after a couple of searches.

Also, photos are copyright National Geographic, not saying they should be off, more pointing people in the right direction for the whole set of photos.
URL: http://ngm.nationalgeographic.com/2009/11/stone-forest/alvarez-photography
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