I. Geologic Time

Frameworks for Geologic Time

*Earth = 4.6 billion yrs. old, but recorded human history ~5000 yrs

= 2 ways of dealing with time.…

 A. Absolute Time
 an actual number
 radiometric dating

B. Relative Time
 relative order of events

Concepts of relative and absolute time combined to create =>

Geologic Time Scale

Units of time

Eon, Era, Period
II.  Relative Time

 => Relative Dating = sequence of events through time: establishing order in with rocks are deposited and subsequently deformed and altered.......…
 - based on the principle of uniformitarianism

1) Principle of superposition

Oldest layers on the bottom => younger layers near the top

2) law of cross-cutting relationships

3) law of inclusions