1. R ELATIVE D ATING : W HICH C AME F IRST ? Chapter 6 Section 2

2. R ELATIVE DATING Any method of determining whether an event or object is older or younger than other events or objects.

3. R ELATIVE D ATING A principle that states that younger rocks lie above older rocks If layers have not been disturbed An arrangement of rock layers in which the oldest rocks are at the bottom SuperpositionGeologic Column

4. E VENTS THAT DISTURB ROCK LAYERS Fault- a break in the Earths crust along which blocks of the crust slide relative to one another Intrusion- molten rock from the Earths interior that squeezes into existing rock and cools Folding- when rock layers bend and buckle from the Earths internal forces Tilting- when internal forces in the Earth slant rock layer

5. G APS IN THE R ECORD : UNCONFORMITIES Unconformity- a break in the geologic record

6. 3 TYPES OF UNCONFORMITIES Disconformities- missing layer of rock ( most common) Nonconformities- sedimentary rock lies on top of eroded surface ( represents millions of years of missing time) Angular unconformities- exists between horizontal rock layers and rock layers that are tilted or folded CBACBA