Igneous rock forms when magma (hot, molten rock) cools and solidifies. Because igneous rocks originated deep within Earth’s crust, geologists who study them can determine what was happening in Earth’s interior when these rocks were forming. This is different from sedimentary rocks, which record geologic events at Earth’s surface.
To learn about the igneous rocks of Devils Tower select a topic below. Start with Fundamental Geology to learn basic information about igneous rocks. Then proceed to Rocks of the Tower to learn about the rocks that make up the Tower itself. Finally, visit the 50 million years ago section to see the end result of both sedimentary and igneous processes.