the great falls of paterson flows over what type of rock
Great Falls (Passaic River) Geologically, the falls were formed at the end of the last ice age approximately 13,000 years ago. Formerly the Passaic had followed a shorter course through the Watchung Mountains near present-day Summit. As the glacier receded, the river's previous course was blocked by a newly formed moraine. A large lake, called Glacial Lake Passaic, formed behind the Watchungs. As the ice receded, the river found a new circuitous route around the north end of the Watchungs, carving the spectacular falls through the underlying basalt, which was formed approximately 200 million years ago.