[meteorite-list] OT- Non Meteorite Crater Photo

From: Ryan Weidert <ryan.weidert_at_meteoritecentral.com>
Date: Mon, 31 May 2010 21:37:02 -0700
Message-ID: <AANLkTim3L0JTcyZSoHW9OgyaUzNI5X2zyctzgUMBnDjG_at_mail.gmail.com>

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
Received on Tue 01 Jun 2010 12:37:02 AM PDT