1. FIVE STEPS TO BECOMING A… GEOLOGICAL DETECTIVE!
GEOLOGICAL CONCEPTS
FIVE STEPS TO BECOMING A…
GEOLOGICAL DETECTIVE!

2. OUR GOAL: TO INTERPRET GEOLOGICAL STRUCTURES WE SEE, LIKE THE ROADCUT DEPICTED BELOW

3. THE 5 CONCEPTS UNIFORMITARIANISM ORIGINAL HORIZONTALITY
LATERAL CONTINUITY
SUPERPOSITION
LAW OF CROSS-CUTTING RELATIONSHIPS

4. CONCEPT: UNIFORMITARIANISM
USING HISTORY, WE STUDY THE PAST TO UNDERSTAND THE PRESENT…
BUT USING UNIFORMITARIANISM, WE STUDY THE PRESENT GEOLOGICAL PROCESSES TO UNDERSTAND THE PAST GEOLOGICAL PROCESSES (EVENTS THAT HAPPENED MILLIONS OF YEARS AGO)…
DEFINITION: GEOLOGICAL PROCESSES HAPPENING TODAY HAPPENED IN THE PAST…
EXAMPLE: TO UNDERSTAND MOUNTAINS THAT FORMED MILLIONS OF YEARS AGO, WE STUDY HOW MOUNTAINS ARE FORMING TODAY.

5. WHAT ARE THE HORIZONTAL LINES?
APPLICATION 1 OF UNIFORMITARIANISM:
WHAT ARE THE HORIZONTAL LINES?

6. CLUE FROM PRESENT PROCESS…

7. USING TIME LAPSE PHOTOGRAPHY
HERE IT IS AGAIN…
USING TIME LAPSE PHOTOGRAPHY

8. ANCIENT LAKE

9. DRYING UP

10. LEAVING TERRACE LINES

12. APPLICATION 2 OF UNIFORMITARIANISM:
WHAT IS THIS?

13. CLUE FROM PRESENT PROCESS…
FROM ANCIENT MUD FLAT
OR SAND DUNE
THEY MUST HAVE SOLIDIFIED INTO ROCK

14. EXPLAIN THIS SOLID ROCK…
APPLICATION 3 OF UNIFORMITARIANISM:
EXPLAIN THIS SOLID ROCK…

15. CLUE FROM PRESENT PROCESS…
GRAVEL
RIVERBED
BEACH
THEY MUST HAVE SOLIDIFIED INTO ROCK

16. FROM UNIFORMITARIANISM COMES THE OTHER 4 CONCEPTS
ORIGINAL HORIZONTALITY
LATERAL CONTINUITY
SUPERPOSITION
LAW OF CROSS-CUTTING RELATIONSHIPS

17. CONCEPT: ORIGINAL HORIZONTALITY
SEDIMENT LAYERS ARE USUALLY DEPOSITED HORIZONTALLY
THUS, LOOK FOR LAYERS NO LONGER HORIZONTAL TO RECOGNIZE THAT FORCES ACTED ON THE LAYERS AFTER FORMATION

18. APPLICATION OF ORIGINAL HORIZONTALITY:
FINDING TILTED AND FOLDED LAYERS
WHAT HAPPENED TO THE LAYERS HERE?
THEY WERE FOLDED
BY FORCES PUSHING TOGETHER

19. SUMMARY OF ORIGINAL HORIZONTALITY
SEDIMENT LAYERS ARE USUALLY DEPOSITED HORIZONTALLY
SO, LOOK FOR LAYERS THAT ARE NOT HORIZONTAL, MEANING SOME FORCE ACTED ON THEM TO FOLD OR TILT THEM
USE THIS CONCEPT TO FIND FOLDS AND TILTED ROCK LAYERS

20. ROCK LAYERS CAN BE TRACED ACROSS WIDE AREAS
CONCEPT: LATERAL CONTINUITY
ROCK LAYERS CAN BE TRACED ACROSS WIDE AREAS

21. APPLICATION OF LATERAL CONTINUITY:
WHAT HAPPENED TO THE LAYERS HERE?
THEY WERE
BROKEN

22. APPLICATION OF LATERAL CONTINUITY: FINDING FAULTS
FORCES ACTED ON THE ROCK LAYERS TO BREAK THEM! CREATING A FAULT (BROKEN ROCK LAYERS).
THEY WERE
BROKEN

23. 2ND APPLICATION OF LATERAL CONTINUITY:
WHAT HAPPENED TO THE LAYER BETWEEN THESE TWO ARROWS?

24. 2ND APPLICATION OF LATERAL CONTINUITY: FINDING EROSION
EROSION REMOVED THE MATERIAL AS THE RIVER CUT DOWNWARD

25. 2ND APPLICATION OF LATERAL CONTINUITY: FINDING EROSION
EROSION REMOVED PART OF THE LATERALLY
CONTINUOUS LAYERS AFTER THE LAYERS WERE FOLDED
UPWARD
WHAT HAPPENED HERE?

26. SUMMARY OF LATERAL CONTINUITY
ROCK LAYERS ARE DEPOSITED (SO CAN BE TRACED) ACROSS WIDE AREAS
SO, LOOK FOR BREAKS IN THE CONTINUITY
AND USE THIS CONCEPT TO FIND FAULTS AND AREAS THAT HAVE EXPERIENCED EROSION

27. CONCEPT: SUPERPOSITION
YOUNGER ROCK LAYERS
USUALLY OVERLIE
OLDER ROCK LAYERS
YOUNGER
OLDER
AS NEW SEDIMENT DEPOSITS ON TOP OF EXISTING SEDIMENT

28. WHICH ROCK LAYER IS YOUNGER?
APPLICATION OF SUPERPOSITION:
WHICH ROCK LAYER IS YOUNGER?
OR B? A?

29. APPLICATION OF SUPERPOSITION: DETERMINING RELATIVE AGES OF LAYERS
ROCK LAYER A IS YOUNGER
NOT B A
<<<<< YOUNGER OLDER >>>>>

30. WHICH ROCK LAYER IS YOUNGER?
2ND APPLICATION OF SUPERPOSITION:
WHICH ROCK LAYER IS YOUNGER?
OR B? A?

31. 2ND APPLICATION OF SUPERPOSITION: DETERMINING RELATIVE AGES OF LAYERS
ROCK LAYER A IS YOUNGER
OR B? A?

32. SUMMARY OF SUPERPOSITION
YOUNGER ROCK LAYERS USUALLY OVERLIE OLDER ROCK LAYERS
SO, LOOK FOR ROCK LAYERS ONE ON TOP OF THE OTHER
USE THIS CONCEPT TO FOLLOW THE HISTORICAL SEQUENCE OF EVENTS HAPPENING AT A GIVEN SPOT

33. CONCEPT: LAW OF CROSS-CUTTING RELATIONSHIPS
INTRUDING ROCK IS YOUNGER THAN THE ROCK INTO WHICH IT INTRUDES
MAGMA INTRUSION: CALLED A DIKE
MOLTEN ROCK: CALLED MAGMA

34. APPLICATION OF CROSS-CUTTING RELATIONSHIPS:
WHICH ROCK IS YOUNGER? A?
OR B?

35. A? “B” IS YOUNGER BECAUSE “B” INTRUDED THROUGH LAYER A
APPLICATION OF CROSS-CUTTING RELATIONSHIPS:
DETERMINING RELATIVE AGE OF ROCKS
“B” IS YOUNGER BECAUSE “B” INTRUDED THROUGH LAYER A
INTRUSION A?
OR B?

36. SUMMARY OF CROSS-CUTTING RELATIONSHIPS
INTRUDING ROCK IS YOUNGER THAN THE ROCK INTO WHICH IT INTRUDES
SO LOOK FOR INTRUSIONS, ROCK THAT IS DIFFERENT FROM AND CUTS THROUGH OTHER TYPES OF ROCK
USE THIS CONCEPT WITH SUPERPOSITION TO FOLLOW THE HISTORICAL SEQUENCE OF EVENTS HAPPENING AT A GIVEN SPOT

37. REVIEW 1 1. HOW CAN YOU APPLY ORIGINAL HORIZONTALITY? 1
A. LOOK FOR LAYERS NOT HORIZONTAL TO FIND FOLDS AND TILTED ROCK 2
2. HOW CAN YOU APPLY LATERAL CONTINUITY? 3
A. LOOK FOR BREAK IN CONTINUITY TO FIND FAULTS AND EROSION
3. HOW CAN YOU APPLY SUPERPOSITION?
A. TO DETERMINE THE HISTORICAL SEQUENCE OF EVENTS HERE

38. REVIEW 2 WHICH IS YOUNGER… LAYER 2 LAYER 1 1. LAYER 1 OR 2?
A. LAYER 2 SUPERPOSITION
2. LAYER 2 OR DIKE B?
A. DIKE B CROSS-CUTTING REL.
3. VOLCANO A OR B?
A. VOLCANO A
LAYER 2
4. FAULT A OR B?
LAYER 1
A. FAULT A