Relative age and fossils terms
trace fossil
A type of fossil that provides evidence of the activities of ancient organisms
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
Intrusion
always younger than what it cuts thru
fault
always younger than what it offsets
index fossil
fossils of widely distributed organisms that lived during only one short period. used to identify the ages of rocks.
index fossil
occurs in many locations, lived short period of time, can be used to tell the age of a rock layer (without getting radiometric ages)
law of superposition
oldest at the bottom, youngest at top
crosscutting relationships
states that an igneous intrusion (or fault) is always younger than the rock it cuts across.
absolute age
the real age of a rock layer calculated with radioactive decay
unconformity
time of erosion, much younger in contact with older