1. How do we know what happened millions of years ago?
Geologic Time
How do we know what happened millions of years ago?

2. never lived at the same time
Why is this statement false: “The caveman had dinosaur for breakfast.”?
man and dinosaurs
never lived at the same time

3. Fossils can only be found in rocks.
sedimentary

4. Relative Dating
Determining the age of rocks or events in relation to the age of other rocks and rock forming events

5. Principal of Original Horizontality
Rocks form in horizontal layers parallel to earth’s surface.
These layers are known as STRATA

8. Deformed or Distorted Layers
Rocks that no longer show original horizontality

9. Folded Strata

11. Faulted Strata

13. Tilted or Uplifted Strata

14. Relative Age
If a sedimentary rock outcrop has not been overturned, which layer would be the oldest?

15. Principle of Superposition
oldest rock layers are on bottom
Rocks get younger as you move up towards the surface

16. Using this principle, label the strata below from oldest to youngest.

17. Law of cross cutting relationships
Rocks are older
than any fault,
intrusion, or other feature
that cuts across them

20. there first (it's older)
Which is older:
F or S
How do you know?
S= rocks
F= fault
F cuts through S
S must have been
there first (it's older)

21. Faults are always (older, younger) than the rocks they cut through.

22. Put these in order from oldest to youngest

23. When magma squeezes into pre-existing rocks and crystallizes
Igneous intrusions & extrusions
When magma squeezes into pre-existing rocks and crystallizes
What happens when magma touches rocks??

24. Put these in order from oldest to youngest

25. Put these in order from oldest to youngest

26. Put these in order from oldest to youngest

27. If a geologist finds an igneous sill, how can she determine if the sill is an intrusion or an extrusion?

28. contact metamorphism on all sides
Intrusions
contact metamorphism on all sides

29. no contact metamorphism on top
extrusions
no contact metamorphism on top

30. Is “H” an intrusion or extrusion? How can you tell?

31. H is an intrusion. Contact metamorphism on top

32. a buried erosional surface
What is an unconformity?
a buried erosional surface
How does it complicate the relative dating of rock layers?
a part of the rock record
is missing

33. weathering and erosion Animation!!
What processes could lead to an unconformity?
weathering and erosion
Animation!!

35. Using the diagram to the left, identify where the unconformity is located by drawing an arrow and writing the word “unconformity” next to it.

36. Put these in order from oldest to youngestX
Put these in order from oldest to youngest

37. Z X Y

38. What do fossils tell us about
Earth’s History?

39. What characteristics must fossils have in order to be good index fossils?
lived over a large geographic area (large horizontal distribution)
lived for a short period of time (small vertical distribution)

40. In geology, this is referred to as CORRELATION
In the diagram below, a geologist has matched up rock layers based on index fossils.

41. Evolution
a developmental process in which an organ or organism becomes more and more complex by differentiation of its parts
Natural selection- (Survival of the fittest)
only the organisms best adapted to their environment tend to survive and transmit their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated

42. Evolution can see that different organisms have changed over time
Explain how the fossil record supports this theory
can see that different organisms have
changed over time

43. ESRT Page 8 & 9

44. Using pages 8 & 9 of the ESRT’s
Answer the questions starting on page 6
in your notes

45. Absolute Age The actual age of a fossil or rock layer
How is it determined?
Radio-active dating

46. their half-lives are constant
Absolute Age
Why are radioactive isotopes useful in
determining the absolute age of a rock?
their half-lives are constant

47. NOTHING! it is reliable to calculate age
Absolute Age
What can be done to change the
half-life of a radioactive isotope?
Why is this important?
NOTHING!
it is reliable to calculate age

48. Half Life
The amount of time needed for HALF of the radio-active element to decay
The Half-life NEVER changes
Page 1 of the ESRT’s

49. We use a ratio between parent to daughter will tell you how many half-lives have gone by.

50. One half-life.
50% parent
50% daughter
1 half life

51. Two half-lives.
25% parent
75% daughter
2 half lives

52. Three half-lives.
12.5% parent
87.5% daughter
3 half lives

53. Four half-lives.
6.25% parent
93.75% daughter
4 half lives

54. How many half lives does there will always be some trace amounts left
Absolute Age
How many half lives does
it take to get to 0%?
We will never get to 0%
there will always be some trace amounts left

55. stable atoms unstable atoms Draw the generic graph for the
half-life of a radioactive isotope.
stable atoms
unstable atoms

56. carbon-14 What radioactive isotope could be
Absolute Age
What radioactive isotope could be
used to determine the absolute
age of material that was recently living?
carbon-14

57. Carbon 14 Decays into Nitrogen 14
Used to find the age of living organisms within the last 50,000 years
1 HL= 5,700 years
2HL= 11,400 years
3 HL= ?????

58. Potassium 40- Used for old rocks
Known as K 40
Turns into Argon 40
Dates rocks
1 HL= 1.3 Billion years
2 HL = 2.6 Billion years
3HL = ???????

59. Uranium 238- used for REALLY old rocks
U-238 turns into Lead 206
Used to find the age of the oldest rocks
1HL = 4.5 Billion Years
2 HL= 9.0 billion years
Can we find a rock that has gone through 2 Half lives?????

60. 3 half-lives x (5.7 x 103) =1.71 x 104 = 17,100 years
If there is a 100g sample of C14, how many grams of
C14 would remain after three half-lives?
How long would this take? Show all work.
100g 
50g 
25g 
12.5g
3 half-lives x (5.7 x 103) =1.71 x 104
= 17,100 years