Principles of Stratigraphy

Stratigraphy is the study of rock layers (strata) and their sequence. Its key principles include the Law of Superposition, which states that oldest layers are at the bottom, and younger layers are at the top. The Principle of Original Horizontality suggests that sediment layers initially form in horizontal sheets. The Principle of Lateral Continuity posits that layers extend in all directions until they thin out or encounter a barrier. Lastly, the Principle of Cross-Cutting Relationships indicates that if a rock or fault cuts through others, it is younger than the layers it disrupts. These concepts help geologists understand Earth’s history.