re: #78 Altermite

USGS disagrees as far as fracking/earthquakes. Certainly appears to be some sort of positive correlation between frequency of the two, even if specific incidents are not always possible to link.

Exactly. Thought experiment for DF.

Solid land and substrata. Break up layered substrata and suck out the bursa filling to leave a cavity. Taking gravity and planet spin into consideration, what do you think will happen?

Go out to your larges planter. Use a water hose to blow water up the bottom drain hole so dirt is washed away and out the bottom. What happens to the dirt at the top of the planter? Does the soil fracture and more along a line in the soil? If there were rocks in the planter for drainage do they not move against each other?