The Crooked River Caldera was created by the sudden collapse of overlying rock into an underground reservoir of molten rock.
Around 30 million years ago massive amounts of ash and debris resulting from the eruptions of nearby volcanos filled the caldera and hardened into rock. Smith Rock Tuff–the largest rock formation on the western rim was the outcome, creating massive walls and spires up to 550 feet.
Flows of basalt lava then poured into the area over half a million years ago from vents almost 50 miles away, creating the cap on the tuff in the caldera.
The Crooked RIver then made its way through the rock layers to carve the features seen today. At 3200 feet high, the Smith Rock ridgeline rises 600 feet above the river gorge below.
The picnic and campground areas sit on top of the rimrock, which is made up of columnar basalt.