Isostatic Rebound: Glacial Depression
Only about 10,000 years ago, ice covered all of Canada. Mountains made of ice pushed down on the continent with immense pressure.
For example, the Hudson Bay may have depressed over one kilometer. After the ice melted, Canada began lifting.
We know this because we measure it’s vertical motion with GPS. Imagine squeezing a sponge and watching it return to its shape.
Similarly, isostatic rebound is quick at first, then slows down. This process of glacier rebound is due to the asthenosphere behaving in a fluid manner.
Because ice had been removed, the compressional force no longer exists.