It's obviously a sink hole. They are happening all the time.
The stupidity of this statement is absolutely astounding. I'm not even going to bother trying to prove RET or FET this time around, I'm just going to disprove this stupid statement.
Consider Meteor Crater in Arizona:
Now, consider your average sinkhole:
Do these two look related in
any way!? No, and there's even more evidence to back this up. Consider this: the largest sinkhole
ever discovered was only about 80 metres in diameter. Now, consider this: the smallest known confirmed impact crater resides in Maharashtra, India, and is already 1.2 kilometres in diameter. There's no way that any "sinkhole" could create an "impact crater" that large.
Do your research next time Yendor before you make a complete fool of yourself.