Magma is stored below the surface in reservoirs called magma chambers. It creates and follows paths called conduits to the surface. This network is often referred to as the volcano's plumbing system. These networks can cover vast areas. When magma cools and solidifies in these spaces, intrusive features like stocks, laccoliths, sills, and dikes are formed. If the conduits are emptied after an eruption, they can collapse in the formation of a caldera, or remain as lava tubes and caves.

Devils Tower is believed to be an ancient intrusive igneous rock body, created 60 million years ago during the Tertiary period. Learn more about Devils Tower by opening the case study.