eon
longest time unit
era
2nd longest time unit
periods
defined by life forms
epochs
small divisions of time-millions of years
uniformitarianism
the processes occurring today have been happening for the earths entire life
original horizonality
sedimentary rocks are deposited in horizontal layers
superposition
in undisturbed rock sequence, the oldest rocks are on the bottom
cross cutting relationships
the intrusion or fault is younger than what it curs across
unconformity
gap in the rock record
correlation
the matching of outcrops in different geologic locations
dendrochronology
tree ring dating
varves
alternating light and dark coloured sediments
key bed
time markers