Question

why folds depend on the strength of rocks and intensity of forces​

Answer 1

Rocks that were originally deposited in horizontal layers can subsequently deform by tectonic forces into folds and faults. Folds constitute the twists and bends in rocks. Faults are planes of detachment resulting when rocks on either side of the displacement slip past one another.

Answer 2

Answer:

The way in which rocks are deformed and new structures are formed depends on the strength and intensity of the forces applied to them.

They can be deformed either by compressive, tensional and shearing forces. So it depends on the strength of rock as to whether it forms a folded structure or anything different. The type of force and the strength and structure of the rock determines the extent of deformation of rock and thereby the final structure.