How do waterfalls form? The Cascade Range is made of volcanic layers from numerous eruptions over the last 35+ million years. The layers, or deposits, originated from numerous sources, each having a different resistance to erosion. They were then uplifted after the volcanic activity stopped. The stream’s erosive energy continues to carve the channels that we see today.

Waterfalls develop when downcutting streams breach through a resistant bedrock layer into the softer material beneath. The height of the waterfall is dependent upon the thickness of the resistant bedrock layer through which the stream erodes.

Do waterfalls change? Energy from plummeting water creates a plunge pool at the base of the waterfalls, eroding a cavity in the softer underlaying rock. This process undermines the resistant layer, causing it to break apart, piece by piece, along cracks and fissures. Through this process, waterfalls gradually migrate upstream. Over the course of thousands of years, this movement can be a few to several feet.

Are there different types of waterfalls? Water plummets over ledges of basalt in eight forms. While most falls have elements of more than one form, the examples shown are most representative of each type.