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