Scotia Bluffs form a 2-mile (3-kilometer) series of gray sandstone cliffs along the north bank of the Eel River near Rio Dell, California.

The course of the lower Eel River changes from northeasterly to westerly as it encounters the resistant Rio Dell Formation of fossiliferous upper Pliocene marine sandstone 15 miles (24 kilometers) inland from the Pacific Ocean.

River turbulence has created deep pools beneath steep sandstone cliffs on the northeasterly bank.

Tributary streams, including Nanning Creek, cut steep, narrow canyons through the cliffs.

These trestles and benches have been frequently damaged by floods and by massive blocks of sandstone falling from the upper cliffs.