What Is a Rock? Rock Types, Classification, and Geologic Tools Explained | Interlude A from Earth: Portrait of a Planet
What Is a Rock? Rock Types, Classification, and Geologic Tools Explained | Interlude A from Earth: Portrait of a Planet What exactly is a rock, and why do geologists care so much about how it forms? In Interlude A of Earth: Portrait of a Planet , Stephen Marshak lays the groundwork for all of geology by defining the concept of a rock and introducing the genetic classification system that guides modern Earth science. For a clear and engaging summary, watch the chapter video on YouTube , or read below for a comprehensive guide to rocks and how we study them. What Is a Rock? The Geologic Definition Rock Definition: A rock is a coherent, naturally occurring solid composed of an aggregate of minerals, mineral grains, or glass. Clastic vs. Crystalline: Clastic rocks are made from cemented fragments, while crystalline rocks have interlocking mineral grains. The Three Genetic Rock Classes Igneous Rocks: Formed by the solidification of molten magma or lava (e.g., granit...