It contains layers of differing hardness, cementation, and composition.

The more resistant layers are harder and more durable under erosion.

The less resistant layers wear away more quickly when exposed to the grinding action of water, ice, and the physical and chemical processes that break rock apart over time.

In a typical mountain of softer rock, erosion acts relatively uniformly across the face of the mountain, wearing it down gradually in a way that produces sloping sides.

But when a capping layer of very resistant rock sits atop less resistant material — or when the rock has properties that cause it to break in particular ways along natural joint and fracture lines — the result can be what geologists call a “mesa” or, in the specifically dramatic version of the tepuis, a near-vertical escarpment.