Relative age and fossils terms

Intrusion

Magma that pushes through rocks. Always younger than what it cuts through.

fault

A break in the rock. Always younger than what it offsets.

fossil correlation in geology

By studying their fossil content, geologists can match rock layers that are far away from each other (and even in different parts of the world).

deposition

Process in which sediment is laid down in new locations.

erosion

Processes by which rock, sand, and soil are broken down and carried away

relative age

age of layers in comparison to others

uniformitarianism

is the idea that the geologic processes that operate today also operated in the past (the present is key to understanding the past)

law of original horizontality

law that states that sedimentary rocks are usually deposited flat (horizontally)

principle of crosscutting relationships

principle that states that an igneous intrusion (or fault) is always younger than the rock it cuts across.

law of superposition

states that the oldest sedimentary layers are on the bottom, youngest at top

absolute age

the real age of a rock layer calculated with radioactive decay

unconformity

time of erosion, much younger in contact with older