[Dog Gone]

Why are there marine fossils at the summit of Mount Everest?

When continents collide, the rock formations break, are forced up on their sides, and ancient deep sedimentary rock becomes the mountaintop. A good example of this would be the Himalayas.

[dirtboy]

Or study the depositional sequences in the Appalachians. You have a series of large deltaic formations from successive mountain-building episodes - and those formations in turn were uplifted to form mountains and plateaus, with the original mountains long gone.

Or go out and visit the Maroon Bells outside of Aspen, which are composed of red rock sediments washed off the Ancestral Rockies and then uplifted.