The document discusses geologic time and the geologic column. It is divided into major eons like the Precambrian and Phanerzoic eon. Each eon contains eras like the Paleozoic, Mesozoic, and Cenozoic eras which are further divided into periods and epochs. Laws governing the geologic column are also described, such as the laws of superposition, original horizontality, and crosscutting relationships which are used to reconstruct geologic history and determine relative ages of rock layers.

1. Geologic Time and
Geologic Column

2. Geologic Time
Eons
Eras
Periods
Epochs

3. Eons
There are 2 Major Eons
Precambrian
Phanerzoic

4. The Precambrian
Precambrian Rocks
represent 87% of
Earth History
From 4.5 Byrs to
544 Myrs ago
Majority-Igneous,
Metamorphic, and
some undeformed
sedimentary rocks

5. Phanerozoic Eon
Contains the
Paleozoic, Mesozoic,
and Cenozoic Eras
544 Myrs to present

6. Paleozoic Era
Existed 544 Myrs to
248 Myrs ago
Contains the
Cambrian,
Ordovician,
Silurian, Devonian,
Mississippian,
Pennsylvanian, and
Permian Periods

7. Mesozoic Era
248 Myrs to 65
Myrs ago
Contains the
Triassic, Jurassic
and Cretaceous
Periods
Great Time of
Change

8. Cenozoic Era
65 Myrs ago to
Present
Contains the
Tertiary and
Quaternary Periods
It is the here and now

9. Concepts
Relative Time
Absolute Age
Law of Original Horizontality
Law of Superposition
Law of Original Continuity
Law of Faunal Assemblages

10. Concepts: Continued
Law of Faunal Succession
Law of Crosscutting Relationships
Law of Incusions
Law of Unconformities

11. Relative Time vs. Absolute Age
Relative Age is determined using a
Geologic Column. How do rock strata or
layers relate to each other.
Absolute Age is determined through
radioactive dating and gives an
“absolute” age of the rock.

12. Creating A Geologic Column
We must obey the
previous stated laws
Using the laws we can
reconstruct geologic Obey
events by constructing
a geologic column

13. The Laws
Law of Original Horizontality: All
sediments laid down in water are
horizontal or near horizontal.
Law of Superposition: Undisturbed
sedimentary rocks are older at the
bottom of the formation and younger at
the top.

15. The Laws Continued
Law of Original Continuity:
Sedimentary rocks exist laterally until
the thin or pinch out at their margins.
Law of Faunal Assemblages: Plants
and Animals of the same age will exist
together within the rocks.

17. Laws Continued
Law of Faunal Succession: Different
geologic formations of different ages
will have different fauna.
Law of Crosscutting Relationships: Any
rock cutting another must be younger
that the one it cuts.

18. Crosscutting

19. Last Two Laws
Law of Inclusions: Fragments of another
rock in another rock are older than the
rock they are in.
Law of Unconformities: Rocks above the
unconformity are younger than the
ones below it.

20. What do we have here?

21. Let’s Apply This Now