As we all know, the bigger something is, the harder it is to get it to change. Try to imagine the mechanical and thermal forces necessary to affect something as massive as the earth. They must be incredibly powerful. In addition, it seems as though they would also have to move slowly - any power this great would rip the earth to shreds if it happened too fast. So what we have are immense forces acting at a very slow, but persistent, rate.
Scientists have great furnaces and can achieve the same temperatures in a lab - no problem here.
We also have great presses to simulate an increase in pressure. So far so good. But the earth does the same thing, and keeps it hot and bothered for millions of years. This uncertainty can be the curse, or the blessing, of any study of the earth. Never hesitate to make up GeoFantasies about what you see.