How the River Cut the Mountain

Here's the puzzle that ought to stop you: a river always takes the easy way, downhill, around obstacles. So how in the world did this river cut straight through a mountain ridge — through the single hardest rock in the whole region — instead of going around the end of it?

The answer is a matter of who got here first. The rock on top of Kittatinny Ridge is Shawangunk quartzite, laid down over four hundred million years ago — brutally hard stuff, which is exactly why the ridge still stands when the softer land around it has worn away. But the river is older than the ridge in its present form. As the land slowly, slowly bulged up over millions of years, the river was already there, running across it — and it simply sawed downward as fast as the land rose, holding its course, grinding a notch straight down through the rising rock. The mountain went up; the river cut down; and it was a dead heat that the river won. Geologists call it a water gap, and this is one of the most famous in the world.

So you're not looking at a valley the river found. You're looking at a wall the river refused to go around — a thousand feet of the hardest rock in Pennsylvania, cut through by nothing but water and time and sheer persistence. Keep that stubbornness in mind. It turns out to be the theme of this whole valley.