Here's why:
* Intrusion: Igneous rocks form from molten magma that cools and solidifies. When this magma intrudes into existing rock layers, it cuts across them.
* Younger Rock: The igneous rock that formed from the intrusion is clearly younger than the rocks it cut through. It couldn't have existed before the other rocks were there to be cut.
The Law of Cross-Cutting Relationships is a fundamental principle in geology, helping us understand the relative ages of rocks and events in Earth's history.
