 The park is at an elevation of 1 @,@ 637 feet ( 499 m ) on the Allegheny Plateau , which formed in the Alleghenian orogeny some 300 million years ago , when Gondwana ( specifically what became Africa ) and what became North America collided , forming Pangaea . Although the gorge and its surroundings seem to be mountainous , the area is a dissected plateau . Years of erosion have cut away the soft rocks , forming the valleys , and left the hardest of the ancient rocks relatively untouched on the top of sharp ridges , giving them the appearance of " mountains " . 
