Tiankeng in China

I happen to see this program entitied "Mysterious Sky Caves" on some HD channel called Equator HD (http://www.voom.tv/equatorhd.html) last night and it was pretty fascinating. It was all on these giant sinkholes that formed from underground water flowing under a carbonite rock (such as limestone or dolomite). The water and rains would form some kind of acid that would eat at the carbonite rock til either the ground collapses or erodes into a giant sinkhole, technically known as a karst tiankeng. Without going into the details, if you google "tiankeng" you will find a lot of geological data on it and also some pretty good pictures. I've never heard of them before and apparently, there is a whole bunch of big ones in southern China (Guangxi province).

I've been to Guangzhou province because that is where my father grew up but never heard of them until last night. If you can catch it on Equator HD, it's got some cool photography of the underwater cave system.

Jay