You are asking
What happens in this situation?
What happens immediately after this mass forms?
What happens over a million years?
Over a billion years?
For starters, those are 4 questions, and we want 1 question per post. Then, answering each of them would take an entire university class, at least, if you had specified what you are looking for.
But, and this makes things worst, you didn't. You just asked what happens.
What happens to what? Geology? Weather? Numismatic? Ermeneutics? History of furniture crafting technique?
Basically you are asking one of the questions clearly listed in our help center under "which question should I avoid asking?"
you are asking an open-ended, hypothetical question: “What if ______ happened?”
If you can remove all those issues than your question becomes answerable according to our standards.