1. GEOLOGIC HISTORY

2. UNIFORMITARIANISM “THE PRESENT IS THE KEY TO THE PAST”
What is happening today geologically must have happened in the past.
Ex. Weathering and Erosion, Plate Tectonics, etc

3. Relative Age vs. Absolute Age
Relative - Age of rock or event is compared to ages of other rocks or events in a geologic sequence
Absolute Age – Actual Age

4. RELATIVE AGE
(Determining Sequence of Events)

6. Law of Original Horizontality
1.Sediments are deposited in horizontal layers

7. 2. Law of Superposition Youngest layer is on top, oldest is on bottom

8. 3. Igneous Intrusion
Younger than surrounding rock, look for contact metamorphism in layer above and below the intrusion

9. Which letter represents the intrusion?

11. 4. Igneous Extrusion
rocks that formed from lava that reached the surface of the earth
Younger than the rock layers below and
Older than any rock layer above it
Look for contact metamorphism on the bottom only

14. Which letter represents the extrusion?D

15. 5. Faults, folds, tilting of rock layers - UPLIFT

16. Fault Cracks in rock layers, layers are ________
(rock layers are no longer even)
off-set

18. Folds
Bends in rock layers due to plates converging.

20. Tilting of rock layers
Rock layers are now at an angle

24. 6. Fossils
Are same age as rock they are found in the living organism lived during the time the rock layer was forming

25. 7. Unconformity Buried erosional surface
>> uplift, erosion, subsidence, deposition
Time gap in the rock record
Indicated by a wavy line on diagrams

26. UNCONFORMITY
Draw an arrow to the unconformity
UNCONFORMITY

27. Subsidence – opposite of uplift, sinking of land usually caused by erosion
Isostatic balance – crust on asthenosphere  if pushed up somewhere it will sink somewhere else

32. Sequence the Event
1. Limestone 2. Sandstone (D) 3. Igneous Extrusion (C) 4. Shale (B) 5. Sandstone (A)

33. Sequence the Events

34. A B C D E F G X H I J K L Y
Relative Age: List the following rock layer in chronological order starting with the oldest layer.