Smith Rock State Park years ago, a large caldera was formed when overlying rock collapsed into an underground lava chamber. This created a huge amount of rock and ash debris that filled the caldera. That material solidified into rock, becoming Smith Rock tuff. Rhyolite flows intruded along faults in the Smith Rock Tuff. A half million years ago, basalt lava flows from nearby volcanoes covered the older tuff. More recently, the Crooked River cut its way through the layers of rock to create today's geographic features. Smith Rock itself is a -high ridge (above sea level) with a sheer cliff-face overlooking a bend in
West Rock Ridge is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges of West Rock Ridge a distinct reddish hue. The rock, which formed 200 million years ago during the late Triassic and early Jurassic periods, frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance. Huge slopes made of fractured rock scree are visible beneath many of the ledges of West Rock Ridge. The ridge is the product of a huge feeder dike that supplied several massive lava flows hundreds of feet deep that welled up