Volcanic processes in and around Zion National Park have created spectacular geologic textbook examples of “inverted topography.” Twelve times over the last 1.5 million years, basaltic lava flows have flowed over the landscape and down the Virgin River or its tributaries, and have blocked the drainage and many tributaries. Today, in some locations these igneous rocks stand out in higher relief creating this inverted topography, demonstrating both the differing durability of the hard basalt and the surrounding soft sedimentary strata, and the exceptionally high rate of erosion. The Crater Hill lava flow in the park is one such example emanating from Crater Hill cinder cone in the southwestern corner of the park, and damming both the Virgin River and Coalpits Wash about 300,000 years ago. Parts of six separate lava flows are fond within the park representing two major source areas.