That is an insightful and usful point Filk.

Earth is always on the move, constantly, if slowly, changing. Temperatures rise and fall in cycles over millions of years. The last ice age occurred just 16,000 years ago, when great sheets of ice, two miles thick, covered much of Earth's Northern Hemisphere. Though the ice melted long ago, the land once under and around the ice is still rising and falling in reaction to its ice-age burden.

This ongoing movement of land is called glacial isostatic adjustment. Here's how it works: Imagine lying down on a soft mattress and then getting up from the same spot. You see an indentation in the mattress where your body had been, and a puffed-up area around the indentation where the mattress rose. Once you get up, the mattress takes a little time before it relaxes back to its original shape.

Steve objects to my lay description of lighter and drierI used to simplify and communicate better, as we pump out water or gas or oil. Fracking poisons ground water and leads to earthquakes. Sometimes it leads to subsidence. I am most familiar with NY and midwest to Michigan which is still rising like an unburdened mattress. In Maryland just south of the former ice shelf we are sinking half a foot over the next 100 years. All this data is obtained by NOAA satellites.