The Yandangshan Caldera was a combined result of acidic lava explosion, effusion, extrusion and intrusion forming different rock facies, accumulation of ground surge, pyroclastic flow, air fall, base surge, rhyolitic lava, dome and secondary volcanic rocks. It also displays vivid lithological units, profile, flow units and structures. Yandangshan has almost all types of rhyolitic rocks and is therefore named the Natural Museum of the Rhyolitic Volcanic Rocks.