1. Geologic Time Vocabulary chapter 10- pg. 308
Absolute time/age
Archean
Cenozoic
Era
Epoch
Fossil
Geologic timetable/Scale
Half-life
Isotope
Index (guide) fossil
Relative time/age
Mesozoic
Paleozoic
Key bed
Uncomformity
Period
Radiometric Dating

2. Bellringer WELCOME BACK! Come get a note packet from the front desk!
You have 15 minutes to finish your geologic timeline – don’t forget drawings and coloring
When finished turn in by posters in back.

3. Geo Time Objectives Explain how fossils form
Identify the different types of fossils
Describe what fossils tell about organisms and environments of the past.
State the law of superposition
Describe how geologists determine the relative age of rocks
Explain how index fossils are useful to geologists
Explain what happens during radioactive decay
Describe what can be learned from radioactive dating
Explain why the Geo Time scale is used to show Earth’s History
Describe the different units of the Geologic Time Scale

4. I. Geologic Time Table (6 min)

5. A. Geologic Time Table
1. Summary of major events in Earth’s history preserved in the rock record
2. Fossils are an important part of this record
3. Rocks from different countries can be matched based on the fossil record

6. B. Geologic Time Divisions
a. Eras
b. Periods
c. Epochs
Based on major changes to plant or animal life
-Longest segment of geologic time
-Divisions within the Eras (differ in plant & animal life.)
-Divisions within the Periods( shorter changes.)

7. Trilobite

8. Triops and Sea Monkeys

9. C. Major Eras Precambrian 1. Archean Era 2. Proterozoic Era
a. Earliest rocks formed in the Archean Era
b. Little if any fossils
a. Marked by rocks containing fossils of simple oceanic plants and worms
b. No evidence of life on land
Precambrian

10. C. Major Eras 3. Paleozoic Era 4. Mesozoic Era
a. Fossils contain both aquatic and non-aquatic plants and animals
a. Dinosaurs present

11. C. Major Eras 5.Cenozoic Era
a. Began approximately 65 million years before present and continues Today
b. Many mammals appear
c. Ice age and man are relatively recent events

12. D. 3 things to remember 570 million years ago- life on land began
250 million years ago- Dinosaurs form
65 million years ago- extinction of dinosaurs & mammals form

13. Reading the Rock Record
II. Telling Time
Reading the Rock Record

14. Understanding Time Which scientist must understand time? Geologist
Astronomers
Paleontologist
Meteorologists
Climatologists
Volcanologists
Oceanographers
Mineralogists
Petrologists: studies rocks in-depth.

15. A. Time Determination 1. 2 Time Types a. Absolute Time
Mount St. Helens May 18, 1980
A. Time Determination
1. 2 Time Types
a. Absolute Time
1.) Measured time. Radioactive dating made this possible
2.) Method of recording events that identifies the actual date the event occurred
3.) Difficult and expensive to determine for events before recorded time

16. b. Relative Time
1.)Based primarily on fossils and the principle of superposition

17. 2. Understanding Time 1.) Why is it important?
a. “The present is the key to the Past”
b. If the time of two events are known, the interval between them can be calculated

18. B. Determining Relative Time
3 rules:
a. Law of superposition
1.) In a sequence of undisturbed sedimentary rocks, the oldest rocks will be at the bottom
b. Law of crosscutting relationships
1.) Igneous rocks are younger than the rocks they intrude into
c. Law of included fragments
1.) Pieces of one rock found in another must be older than the rock they are found within

19. Law of Crosscutting Relationships
What’s it really mean?
Law of Superposition
Law of Crosscutting Relationships

20. Law of Included Fragments
What’s it really mean?
Law of Included Fragments

21. C. More Relative Time Information
1.Unconformity
2. Causes
3. Results
Place in the rock record where layers of rock are missing
Layers deposited and then removed
Geologic Time Gap, no sediments were preserved.

22. Unconformities Examples
Unconformity
Unconformity

23. Let’s Sequence! Turn your note packet over to the blank side.
Listen for further directions.

24. Draw and Complete this Sequence

33. Journal # 17 (4/1/13)
Summary: Black Text. Pg. 599 #1-2 -Draw a pattern example for EACH of the three rules of rock sequencing in your comp. book.

34. Geo Time Topic Questions

35. Earth Science Bellringer
Get out your comp.book. Put it at the front of your desk so I can stamp Vocab and the Geo Time Bellringer.
Get out your notes and turn to the blank back page.

36. 4. Order the rock layers from young to old.5

37. Final Round!

38. HW: Due next class Create your own Geologic Rock Layers Include:
12 layers total- colors & designs
Give each layer a letter (Not in order.)
One tilt, fault, or fold
Two unconformities
One Intrusion
One included fragment
Put answers on the back.

39. Everyday is a Holiday! Government Day!

40. C. Use of Fossils Shows changing life- evolution
Index/guide fossils- identify relative age of rock
1.) easy to recognize
2.) occur over a large area
3.) only existed for a short period, few rock layers
Key bed- rock layer used as an index fossil
C. Use of Fossils

41. Geologic Time Bellringer: 1. Order the fossil’s from youngest to oldest. Hint: Some fossil may be the same age. (There should be 8 fossil levels.) True/False 2. Fossil’s are only found in one layer. 3. Older fossil’s are located in lower rock layers. 4. Fossil’s are found in metamorphic rock. 5. Fossil’s can be from plant or animals.

42. Geologic Time Bellringer Answers:
1.) 1.Shark’s Tooth & Ichthyosaur
2. Ammonite
3. Pelecypod
4. Gastropod & Forminifers
5. Crinoid & Placoderm
6. Horn Coral
7. Eurypterid & Graptolite
8. Trilobite & Brachiopod
True/False
2. Fossil’s are only found in one layer.
3. Older fossil’s are located in lower rock layers.
4. Fossil’s are found in metamorphic rock.
5. Fossil’s can be from plant or animals.

43. III. Fossils & Measuring Absolute Time

44. A. Fossil
-any evidence of earlier life preserved in rock

45. B. Types of Fossils Original remains- actual, unchanged remains
Amber- remains in hardened sap

46. 3. Mold- shape of material remains, filled in by new material called a cast.
4. Trace fossils- impression left by an animal & plants
ex. Footprint, tracks, burrows

47. C. Use of Fossils Shows changing life- evolution
Index/guide fossils- identify relative age of rock
1.) easy to recognize
2.) occur over a large area
3.) only existed for a short period, few rock layers
Key bed- rock layer used as an index fossil
C. Use of Fossils

48. D. How is absolute time determined?
1.View the event
Mount St. Helens May 18, 1980

49. 2. Radioactive decay All materials contain radioactive elements
a. These elements decay at a specific & constant rate, called a half-life.

50. Uranium 238 Decay

51. 3. Half-Life
- Time required for ½ of the atoms of a radioactive element to decay to a stable end product

52. Let’s Draw Some ½-lifes.
- Draw five equal sized square on your paper.

53. Half-life Example Parent Material =1g Time = 0 Parent Material = 1/2g
After 1 half-life
Parent Material = 1/4g
After 2 half-lives
Parent Material = 1/8g
After 3 half-lives
Parent Material = 1/16g
After 4 half-lives

54. Half-life Challenge Questions:
1. You have an isotope with a half-life of 100 years. How much of the original material is left after 500 years?

55. Half-life Challenge Questions:
2. What is the half-life of an isotope after 1000 years, if there is 3 times more stable product than unstable product?

56. Half-life Challenge Questions:
3. You have 0.25 grams of an unstable element and 1.75 grams of a stable product. How many half-life’s has it undergone?

57. Half-Life Example