No, sediments do not sink into the earth because they are too light. They stay on the surface and over very long times they form the continents. But they can get buried under many km of other sediments as parts of the crust they
No, sediments do not sink into the earth because they are too light. They stay on the surface and over very long times they form the continents. But they can get buried under many km of other sediments as parts of the crust they're on subsides or is pushed over other parts. Thus they can get into pressure/temperatue conditions where diagenesis (see other answer) or metamorphism alter them.
On a very general level, plate tectonics keep the crust in motion. It can cause