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
Hell's Half Acre Lava Field lava plain is located in Bingham and Bonneville counties in the state of Idaho. The site is about in size. The area where a former lava lake existed is marked by a long by wide depression near the summit of the lava field. Ten circular pits and two large lava tubes are also located near the summit. Two major lava flows, each about long by wide, extend from the main lava field to the south and southwest. These two lava flows surround "Morgans Pasture," a kipuka (or older geologic feature which was not covered by lava). More recently, scientists studying