What is the law of inclusions?

The law of inclusions is a principle in geology that states that a rock formation that contains fragments of another rock within it must be younger than the fragments it contains. This is because the fragments, known as inclusions, are already existing pieces of rock that were incorporated into the new formation as it was formed.

This principle is often used by geologists to determine the relative ages of different rock formations and to construct a timeline of geological events. By studying the inclusions within a rock formation, geologists can infer the sequence in which different formations were created and the relative timing of different geological processes.

The law of inclusions is based on the principle of cross-cutting relationships, which states that geologic features that cut across other features are younger than the features they cut across. By combining the law of inclusions with other principles of relative dating, geologists can determine the relative ages of different rock formations and construct a comprehensive geological history of an area.