I am writing a story set on a mining colony moon with some very odd geological conditions, and while this idea is admittedly likely impossible to fully make geologically plausible but I wanted to see if there was some way to at least make it sort of plausible
The story is set on a moon that is tidally locked to a gas giant, along side dozens of other moons, all causing extreme tidal forces on the crust, similar to Jupiter's moon Io. Unlike Io, I want the moon's surface to be earth-like, capable of supporting breathable air, liquid water, plants, animals, and of course humans. However, once you go more than thousand or so feet beneath the surface, the tidal effects of the gas giant mean that the ground is undergoing constant rapid churning, with the sort of geological activity that takes thousands or millions of years on Earth happening in days or weeks. The underground is very mineral rich due to the volcanism, very porous, filled with large naturally occurring caves with breathable air, and supports its own parallel eco-system of plants and animals, including predatory megafauna, that were at some point churned under from the surface and then continued evolving to adapt to life underground.
The livelihood of the colony revolves around mining highly valuable minerals, and this process works sort of like ice fishing. The miners living on the stable top layers of earth dig tunnels down to the turbulent deeper layers, set up temporary underground boom towns in the caves with hundreds of miners working against the clock to strip everything they can out before the tidal forces move the minerals deeper underground and the miners with them. When it becomes too dangerous to stay, they haul the whole boom town back up to the surface, send the minerals to be refined, and by then a new trove of minerals has moved underneath their "fishing hole", and the whole process begins again. This cycle can sometimes last months, sometimes only a few days, and it can be very unpredictable how long a mine stays stable before it shifts back to lower layers. This is all obviously very dangerous, not only because of all the usual dangers of mining we see on Earth like flooding, fires, bad air, etc but also because the underground has large predatory creatures, and of course the constantly changing geology that can bury the entire expedition alive.
So that's the setup I want; how can I make it more realistic to actual geology and astrophysics and such while still keeping the core idea? I know there is the example of a highly geologically active moon in Io I mentioned, from what I have read even the quick moving Io is not nearly this quickly moving. Not to mention that Io is a volcanic hellscape and not at all Earthlike on its surface, since all the geologic instability means tons of earthquakes and volcanoes that would make life on the surface impossible. So I am wondering what are some ways that these sorts of geological conditions can exist while still allowing for the moon's surface itself to stay in the same place and be geologically stable and habitable?
My best theory so far is the idea of the surface settlements being mostly built on areas composed of a rock that is much sturdier and more durable than the earth underneath and sort of floats over everything else, allowing largely earth like lifestyle with the only concerns being a relatively high frequency of earthquakes and volcanoes,similar to living along the Ring of Fire on Earth. However, I'm not really familiar enough with geology and plate tectonics and the like to know if this would actually work.
As I said, I am not sure this set up actually can be made totally realistic, but I at least want to do what I can, and please feel free to point out any other issues I maybe neglected to consider.
Thanks
