Here's why this is true:
* Faults and intrusions are geological events that disrupt existing rock formations.
* Faults are fractures in the Earth's crust where rocks have moved past each other.
* Intrusions are bodies of magma that have cooled and solidified within existing rock layers.
The Principle of Cross-Cutting Relationships
If a fault or intrusion cuts through a rock layer, it must have formed after the rock layer was deposited. This is because something cannot be broken or intruded upon unless it already exists.
Example:
Imagine a layer of sandstone being deposited, followed by an igneous intrusion pushing through the sandstone. The igneous intrusion would be younger than the sandstone layer because it cuts through it.
Key Takeaway: The principle of cross-cutting relationships is a crucial tool for geologists to determine the relative ages of geological formations, even if they cannot directly date the rocks using radiometric methods.
