What factors cause the faulting and folding of rocks?

Question

What factors cause the faulting and folding of rocks?

Answer 1

Mechanical stress on rocks causes them to fold and/or fault.  This stress can be compressional (being pushed on from one or both sides) or tensional (being pulled on from one or both sides).  The ultimate cause of almost* all this rock deformation is plate tectonics, without which almost* all stress fields would slowly equilibrate and zero out.  But the continuing dynamism of the earth's mantle and crust assures that new stresses are always being added.

* Hotspots and glacial processes, along with earth tides and other minor processes, would continue to impose stresses on earth's rocks, even in the absence of plate tectonics.

Answer 2

plate tectonics