Originally posted by 2manyquestions
When I was in Europe last Christmas I went to a mining town and read some interesting info. I learned that Slovakia (and I'm sure this is true about a lot of other countries as well) has hundreds of miles of tunnels running under the ground. It also contains many natural caves underground. It's quite possible that if any of these tunnels become unstable someday, they'll create giant sink holes when they cave in. I don't know about this particular sink hole, but it's possible it could be mining tunnels or natural underground caverns (could be small or big, who knows). Even if no modern-time tunnels exist down there, it's possible that previous civilizations could have been mining in the same area. With enough rain, weather, minor earthquakes and ground shifting, it could be the last straw that broke the camel's back. That's just my theory.

edit on 18-1-2011 by 2manyquestions because: (no reason given)