How does the law of crosscutting explain the age of a fault

Answer 1

The law of crosscutting relationships is a principle in geology that helps determine the relative age of geological features like faults. It states that if one geologic feature cuts across or disrupts another, the feature doing the cutting is younger than the one being cut.

When it comes to faults, the law of crosscutting relationships can be applied to understand their age. A fault is a fracture in Earth's crust where rocks on either side have moved relative to each other. If a fault cuts across pre-existing rock layers, the fault must be younger than those rock layers because it is the factor causing the displacement.

For example, let's say there are layers of sedimentary rock that have been deposited horizontally one on top of another for millions of years. If a fault cuts through these layers, displacing them and offsetting their continuity, the fault is younger than the layers it interrupts. This means that the fault must have formed after the deposition of the layers and is responsible for the movement and displacement.

Therefore, by identifying the age of the rock layers and determining which features cut across them, geologists are able to establish the relative age relationship and infer the age of the fault. However, it is worth noting that the absolute age (in years) of a fault can be challenging to determine and often requires additional dating techniques.