Understanding the Principles
* Principle of Superposition: In undisturbed sedimentary sequences, the oldest layers are at the bottom, and the youngest layers are at the top.
* Principle of Cross-Cutting Relationships: Any feature that cuts across existing rock layers is younger than the layers it cuts.
Scenario: Intrusion and Dome Formation
1. Sedimentary Layers: Imagine a sequence of sedimentary rock layers (like sandstone, shale, and limestone) deposited over time. These layers are initially flat.
2. Igneous Intrusion: A hot, molten rock mass (magma) from below rises up and pushes through these layers. This is the intrusion.
3. Domed Structure: The heat from the intrusion causes the overlying rock layers to bend upward, creating a dome-like structure.
Relative Ages
* Igneous Intrusion: The igneous intrusion is younger than the sedimentary layers it cuts through. This is because the intrusion happened *after* the sedimentary layers were already formed.
* Domed Layers: The sedimentary layers that are domed upward are also older than the intrusion. They existed before the intrusion occurred and were subsequently deformed.
In Summary
In this scenario, the igneous intrusion is the youngest feature, and the sedimentary rock layers are older.
