"I'm just wondering if my insurance would cover the loss. Not really an act of God, since it's all been sucked downwards ... ?

If you live in mining country (current or historical), you need to have 'mine subsidence' coverage in your home insurance policy. There are more homes built over mine shafts than most people suspect. Sometimes a shaft or tunnel collapses and a home falls into it. Seeing a house roof sitting directly on the ground (or in it) is a clue.

Sue