[meteorite-list] More on world sinkholes

[Zelimir Gabelica]

Listees,

I was amazed and intrigued by the Guatemala 
sinkhole report, something that always fascinated me.

There are larger such holes around the world, 
natural and not always filled by water.
I remember having overflown by helicopter the 2 
famous big holes in the Sarisarinama region in remote South Venezuela.
This was one of the most impressive views.

Here are some links:

1) General about Sarisarinama:

http://en.wikipedia.org/wiki/Sarisari%C3%B1ama

2) Views (click on clip 5):

http://www.google.fr/imgres?imgurl=http://www.lastrefuge.co.uk/images/filmlibrary/sarisarinama_sink_hole.jpg&imgrefurl=http://www.lastrefuge.co.uk/data/aerials/tepuis_aerial_samples.htm&h=113&w=200&sz=11&tbnid=lwph4FMnj1IrnM:&tbnh=59&tbnw=104&prev=/images%3Fq%3Dsarisarinama&hl=fr&usg=__Kne9TnuqGa3DrTVz1sTqlK87wOw=&ei=NsAETPc6kb3iBuKH-MsO&sa=X&oi=image_result&resnum=3&ct=image&ved=0CCAQ9QEwAg

3) At the time (1995) it was forbidden to 
approach this site by some flying machine (no roads nor paths go there).
On the way to El Paui gold mines (near the triple 
borderline Venezuela-Brazil-Guyana) with an 
expedition, we arranged with some local army 
official while in San Francisco de Yuruani, to 
have a short helicopter flight over the Sierra de Neblina/Sarisarinama sites.
Breathtaking...

Apparently there are now some organized tours 
offering tourists an overflow the area by some small plane of Cessna type.
See here:

http://www.google.fr/imgres?imgurl=http://www.condorjourneys-adventures.com/images/venezuela_sima_map.jpg&imgrefurl=http://www.condorjourneys-adventures.com/venezuela_sarisarinama.asp&h=270&w=299&sz=23&tbnid=zJqrcPIpjAMYwM:&tbnh=105&tbnw=116&prev=/images%3Fq%3Dsarisarinama&hl=fr&usg=__Zc1BSNFSQlulJEfpvqX4oo4qvBM=&ei=NsAETPc6kb3iBuKH-MsO&sa=X&oi=image_result&resnum=2&ct=image&ved=0CB4Q9QEwAQ

Should you wish a less expensive trip, foresee a 
17 days excursion and a very hard walking through jungle:

http://www.abenteuer-venezuela.de/eng/Sarisarinama%20Expedition%20eng.htm

But then you must be in an excellent health shape.
In another expedition (2004), for having walked 
uphills through such a jungle from an improvised 
camp on the rio Churun tributary to rio Carrao, 
up to the bottom of the Salto Angel (Angel Falls 
980 m high), I can just say such a walk it is 
more than hard but really rewarding and truly 
fascinating (especially when you eventually 
refresh under the highest natural shower in the world!)

4) This being, how the sinkholes work ?
Look at this rather complete link, that includes, 
among others, the 2007 Guatemala sinkhole and the 
Sarisarinama geological Karstic-type collapse:

http://science.howstuffworks.com/sinkhole.htm/printable

5) I agree with Werned Schroer that the pics 
showing the sinkhole in Guatemala City could be 
those recorded in Feb 23, 2007.
See  the above link but also a few pics in the 
link below, showing the 5-6 most famous sinkholes 
recorded worldwide, including....Sarisarinama

http://www.environmentalgraffiti.com/offbeat-news/5-giant-holes-devoured-everything-around-them/1196

Compare the outline of the Guatemala sinkhole 
that occurred in 2007 with that shown on the pic 
related to the last May 31 hurricane in the same city (preceding posts).
Almost perfect matching!

6) To complete this issue it is also worth 
looking at the "7 amazing circular geological 
oddities in the world" (of all kind, natural, 
artificial, even of meteoritic origin). For "the 
beauty of art" or to complete your general geoinformation...

http://travel.spotcoolstuff.com/united-states/arizona

Have fun!

Zelimir

At 06:37 01/06/2010, Ryan Weidert wrote:
>Cenotes are sinkholes, simply filled with water.
>
>Sinkholes are usually formed by the collapse of a void underground.
>Typically this happens in limestone/marble/carbonate rocks (where
>caves are normally formed) because rainwater + CO2 (dissolved in H20)
>creates a weak (carbonic) acid that eats at the CaCO3 of the carbonate
>rocks (as it seeps down cracks), and begins creating a gap. As the gap
>gets larger, more water flows in, accelerating  the process, until,
>eventually, a cavity too large to support itself is created an
>collapses, thus creating a sink hole.
>
>Similar processes occur within dirt, however instead of an acidic
>water to eat at and remove rock, flowing water is all that is needed.
>The report of a poor/leaking sewer system is a good indication that
>this sinkhole is probably human caused. Basically, the leaking sewage
>begins eroding the dirt around the pipe as it flows to wherever its
>going. The void gets larger and more 'chunks' of dirt fall into the
>moving water/sewage to be transported away. Since the hurricane just
>went through, its a good bet that the sewers were inundated with
>water, advancing the growth of the void to its collapse point.
>
>The neat thing about this sinkhole is how uniform and open it is. From
>my observations, it seems that sinkholes that form in cites are
>usually like this, as there is no rock to 'plug' the hole which would
>only create a depression. This is indeed a big and deep one.
>
>A very neat place in New Zealnd is covered with sinkholes following
>underground caves. A photo can be seen here
>
>http://davidwallphoto.com/searchresults.asp?t=45&n=25351
>
>cheers
>ryan weidert
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Prof. Zelimir Gabelica
Université de Haute Alsace
ENSCMu, Lab. GSEC,
3, Rue A. Werner,
F-68093 Mulhouse Cedex, France
Tel: +33 (0)3 89 33 68 94
Fax: +33 (0)3 89 33 68 15