Final answer:
An intrusive rock or a fault is younger than the rock layers they cut through.
Step-by-step explanation:
When examining geological formations, an intrusive rock or a fault is always younger than the rock layers they intersect. Intrusions occur when molten rock (magma) penetrates existing rock layers and cools beneath the Earth's surface. As a result, the intrusion is younger than the surrounding rock layers it cuts across. Similarly, faults represent fractures where movement has occurred in the Earth's crust. When a fault displaces layers of rock, the fault itself is formed after the surrounding rock layers have already settled. Therefore, both intrusive rocks and faults are considered younger than the rock formations they disrupt or cut through.
This principle is foundational to relative dating in geology, known as the principle of cross-cutting relationships, where geologists use these relationships to determine the relative ages of geological formations. Hence, the correct relationship is that intrusions and faults are younger than the rock layers they intrude upon or cut through.