Intrusions, extrusions of igneous rocks, and faults and gaps all share a common feature, that is, they help geologists and scientists in determining the relative age of rocks.
Igneous rock is produced when the lava or magma hardens. The lava, which toughens on the surface is known as extrusion. The layers of the rock below an extrusion are always older in comparison to the extrusion. Within the surface, magma may push within the bodies of rock. There, the magma cools and hardens into a mass of igneous rock known as an intrusion.
An intrusion is always younger in comparison to the layers of rock around and beneath it. Even more, clues come from the examination of faults. A fault refers to a break in the crust of the Earth. A fault is always younger in comparison to the rock it cuts through.
