1. Unit 7 - Relative Dating and Fossils
Chapter 9 – Views of Earth’s Past
Section 9.1 – Earth’s past is revealed in Rocks and Fossils

2. Rocks, fossils, and original remains give clues about the past.
Mountain formation, earthquakes, and other changes in Earth’s surface
Dinosaurs
Reptiles
Lived 200,000,000 years ago
Became extinct 65,000,000 years ago
DO YOU KNOW WHY?

3. Scientist believe that a giant asteroid crashed into the Earth causing huge changes in the atmosphere, possibly an ICE AGE.

4. Fossils
Preserved traces or remains of living things from long ago.
Shells, bones, and teeth
Actual organism (original remains), part of an organism, or an impression of an organism
Found where conditions prevent decomposition
Ice
Amber
Tar

5. Fossils
Limited information due to decomposition
Hard items are more easily preserved
Rock fossils form in sedimentary rock.
Igneous rock never contain fossils

6. Mold Fossil
Visible shape that was left after an animal or plant was buried in sediment and then decayed
Cast Fossil
When a hollow mold get filled with minerals, it becomes a solid model of in the shape of the organism
Petrified would
Stone likeness of a tree left when minerals carried by water take the place of the tree cells

7. Carbon Films
Visible layer of carbon left behind when a dead plant or animal decays
Trace Fossils
Preserved footprints, trails, animal holes, and even feces;
Are compared to what is known about modern animals

8. Fossils and other natural evidence show changes in life and the environment.
Read Part 1 of Page 292
Tree Rings
Width of a tree ring tells how much the tree grows in a year
Thin rings suggests a dry year while a thick ring suggests a wet year
Ice Cores
Tubular sample of ice that shows how the layers have built up over time
Scientists observe trapped air and determine information about volcanic eruptions or how long an ice period or warm period lasted

9. Homework
Page 293
#1-4

10. Please take out your homework.
Bell Ringer #13 Tuesday, March 29, 2017
Why might ancient lakes and sea beds be rich sources of fossils?
The hard parts of water organisms, such as shells, bones, and teeth drop to the bottom and get covered by sediment in layers over time.
Questions and answers!
Please take out your homework.

11. Homework Page 293 #1-4
1. What can rock fossils and original remains show about Earth’s past?
They can show what organisms were alive in the past, how they lived, and how Earth’s environment has changed
2. Why do rock fossils form in sedimentary rock and not in igneous rock?
The heat of molten rock destroys the remains of dead plants and animals
Questions and answers!

12. Homework Page 293 #1-4
3. How do tree rings and ice cores help scientist understand how Earth has changed over time?
Tree rings show wet and dry years. Ice cores show how the air has changed and when volcanic eruptions have occurred.
4. If you uncovered fossils of tropical fish and palm trees, what could you say about the environment at the time the fossils formed?
The environment was probably a tropical shore line.
Questions and answers!

13. Unit 7 - Relative Dating and Fossils
Chapter 9 – Views of Earth’s Past
Section 9.2 – Rocks Provide a Timeline for Earth

14. Layers of Sedimentary rock show age.
Relative Age
Age of an event or object in relation to other events or objects
Bottom layer of rock forms first so it is the oldest
If undisturbed , top layer is the youngest
Tectonic plate movement can disturb rock layers
Igneous rock can also disturb sedimentary rock

15. Index Fossils
Fossils of organisms that were common, that lived in many areas and that existed only during specific spans of time.
In relative dating, other fossils can be compared to index fossils to determine when the organism existed.

16. Radioactive dating can show actual age
Radioactivity
The breakdown of unstable elements into another form (isotope) of that element
Half-life
The rate of change for a radioactive element
The length of time it takes for half of the atoms in a radioactive element to change from one form to another

17. Using absolute and Relative age

18. Homework
Page 301
#1-4

19. Please take out your homework.
Bell Ringer #14 Thursday, March 30, 2017
A rock contains a radioactive element with a half life of 100 million years. Tests show that the rock has gone through three half lives. How old is the rock?
300,000,000 years
Questions and answers!
Please take out your homework.

20. Homework Page 301 #1-4
1. What can you tell from undisturbed rock layers? Discuss the concept of relative age in your answer.
You can tell the relative age of rock layers because sedimentary rock forms in layers, with the oldest at the bottom and the youngest at the top
2. How can index fossils help scientists determine the ages of rock layers?
The approximate age of a rock can be determined by comparing it to the age of other index fossils.
Questions and answers!

21. Homework Page 301 #1-4
3. What property of radioactive elements makes them useful for determining absolute age?
Particular radioactive elements always break down at the same rate into another form 2.
4. What are some things in your life for which you only know the relative age?
A flat screen TV may be one example
Questions and answers!

22. Bell Ringer #15 Friday, March 31, 2017
HAPPY FRIDAY. HAVE A SAFE A FABULOUS SPRING BREAK!
New Bell Ringer Policy
Keep your own Bell Ringer Notebook
Bell Ringer Questions are valid Test Questions
Questions and answers!
Please take out your homework.

23. Worksheet 9.1 and 9.2
9.1
1a. Remains of mammoths have been preserved in _____.
Ice
1b. A _____ may form when an animal is buried in sediment and then decays.
Mold
1c. _____ is the stone fossil of a tree.
Petrified wood
1d. A _____ is a type of fossil found in rock that may show detailed images even of soft parts of plants and animals.
Carbon film

24. Worksheet 9.1 and 9.2
9.1
1e. Original remains of insects may be found in hardened tree resin called _____.
Amber
1f. The original remains of ancient animals such as sabertooth cats have been preserved in _____.
Tar
1g. Sand or sediment can harden in a mold to create a _____.
Cast fossil
1h. A fossilized footprint, trail or animal hole is called a _____.
Trace fossil

25. Worksheet 9.1 and 9.2
9.1
2. In what ways are tree rings and ice cores alike? Different?
They both are like timelines that help scientists study the past.
Both show layers that indicate what the climate was like in the past.
Tree rings show whether climate was wet or dry.
Ice cores show times that were warm or cold and what the atmosphere was like.

26. Worksheet 9.1 and 9.2
9.2
Based on the Index fossil Chart, when was each rock formed?
Rock A- Between 144 and 65 MYA (million years ago)
Rock B- Between 206 and 144 MYA
Why are index fossils useful for figuring out the age of disturbed rock layers?
Index fossils can provide appropriate dates for each layer so they can help determine the original order of the rock layers.

27. Worksheet 9.1 and 9.2 9.2 2. Half-life % Uraanium 235 % Lead 207 100 1
100 1 50 2 25 75 3
12.5
87.5

28. Please take out your homework.
Bell Ringer #16 Monday, April 10, 2017
Welcome Back. I hope you had a fabulous spring break!
Carbon 14 has a half-life of approximately 5,700 years. Scientist discover a mammoth bone that has ¼ of its original carbon 14. How old is the bone?
If only ¼ carbon 14 is left, then it has been through 2 half-lives. Sooooo…
2 x 5,700 = 11,400 years old.
Questions and answers!
Please take out your homework.

29. Unit 7 - Relative Dating and Fossils
Chapter 9 – Views of Earth’s Past
Section 9.3 – The geologic time scale shows Earth’s past

30. Time Scale Example Quarter Q1 Q2 Q3 Q4 Unit U1 U2 U3 U4 U5 U6 U7
Chapter C1 C2 C3 C4 C5 C6 C7 C8 C9
C10
C11
Section S1
S1 and S2
S1, S2 and S3
S1, S2, S3 and S4
S1, and S2

31. The geologic time scale shows Earth’s past Earth is Constantly Changing
Who is James Hutton?
The first scientist to present a hypothesis about the Earth changing over time.
What is uniformitarianism?
Earth is an always-changing place
The same forces of change at work today were at work in the past

32. The geologic time scale shows Earth’s past The geologic time scale divides Earth’s history
What is an eon?
The largest unit of time on a geologic time scale
What is an era?
A smaller unit of time which eons are divided into
What is a period?
A smaller unit of time which an era is divided into
What if an epoch?
A smaller division of a era

33. The geologic time scale shows Earth’s past The geologic time scale divides Earth’s history
What are the three eons of the Precambrian time?
Hadean
Archean
Proterozoic
What is the one eon since Precambrian time?
Phanerozoic

34. The geologic time scale shows Earth’s past The Phanerozoic Eon
Began around 544 MYA
Three eras
Paleozoic- ancient life
Mesozoic- middle life
Cenozoic- recent life

35. The geologic time scale shows Earth’s past The Paleozoic Era
All life lived in the ocean
Fish with backbones developed
(Amphibians and) Reptiles, insects and ferns were next
248 MYA a mass extinction occurred ending the era

36. The geologic time scale shows Earth’s past The Mesozoic Era
Dinosaurs ruled
Mammals, birds and flowers appeared
Lasted 183 MY
Ended with another mass extinction possibly caused by one or more giant asteroids hitting the Earth.

37. The geologic time scale shows Earth’s past The Cenozoic Era
Began 63 MYA
Age of Mammals
Divided into two periods
Tertiary period
Quaternary period
The last 2 MY
A series of ice ages
Mammoths, saber-toothed cats and other giant mammals

38. The geologic time scale shows Earth’s past The Cenozoic Era
The first HUMAN fossils are about 100,000 years old
The end of the Quaternary period is defined by human C I V I L I Z A T I O N
Homework
Page 309
#1 - 4

39. Homework : Page 309 #1-4 1. Describe the concept of uniformitarianism.
Forces of change on Earth today are the same as they were in the past. Example: Volcanoes erupt today just as they did in the past
2. What does the geologic time scale measure?
It measures Earth’s history by dividing it into time intervals based on major changes

40. Homework : Page 309 #1-4 3. What was life like on Earth for most of its history?
No plants or animals existed
What period , era, and eon do you live in?
Quaternary period
Cenozoic era
Phanerozoic eon

41. Turn it in at the end of the period
Test Thursday
Test Thursday
IN CLASS ASSIGNMENT
Turn it in at the end of the period
Write out the questions and the answers
Page 313
#1-16
#1-3 (just write the definitions)
Test Thursday
Test Thursday

42. Chapter Review 1. Index fossil
Fossils of organisms that were common, that lived in many areas and that existed only during specific spans of time.
2. Ice Core
Tubular sample of ice that shows how the layers have built up over time, Scientists observe trapped air and determine information about volcanic eruptions or how long an ice period or warm period lasted
3. Original remains
Actual organism or soft part of an organism found where conditions prevent decomposition

43. Chapter Review
4. Which of the following might show evidence of a year with low rainfall?
Tree rings
5. In which time span did dinosaurs live?
b. Mesozoic
6. Half-life is a measurement of-----.
b. Radioactive breakdown
7. What is the age of the Earth?
c. 4.6 BYO
8. What was the earliest form of life?
c. A one-celled organism

44. Chapter Review
9. Which statement best describes the concept of uniformitarianism?
Earth continues to change just as it always has
10. How does petrified wood form?
d. Water seeps through a log replacing its cells with munerals
11. A cast fossil is formed from-----.
b. A mold
12. Which of these best preserves soft parts of an organism?
c. Amber

45. Chapter Review
13. Which part of an ancient reptile would you expect to see in a rock fossil?
b. Bone
14. Which type of fossil would be most likely to show the complete outline of a leaf?
b. Carbon film
15. Why are no fossils found in igneous rock?
Heat and pressure cause the material to breakdown and decay
16. Why is radioactive dating not useful for determining the age of sedimentary rock?
Sedimentary rock is formed from many other rocks which may have varying ages

46. The half-life of carbon 14 is 5,700 years.
How old is a rock that has only 6.25 % of the carbon 14 left?
Half-life
% cabon 14
100 1 50 2 25 3
12.5 4
6.25
4 x 5,700 = 22,800 years

47. Vocabulary Original Remains Mold Fossil Cast Fossil Petrified wood
Carbon Films
Trace Fossils
Tree Rings
Ice Core
Relative Age
Absolute Age

48. Short answer
1.What type of conditions would prevent decomposition?
Ice, Amber or Tar
2.What do tree rings tell us?
Width of a tree ring tells how much the tree grows in a year
Thin rings suggests a dry year while a thick ring suggests a wet year
3.Why might ancient lakes and sea beds be rich sources of fossils?
The hard parts of water organisms, such as shells, bones, and teeth drop to the bottom and get covered by sediment in layers over time.

49. Short answer
4.How do layers of sedimentary rock show age?
Oldest layer at the bottom; youngest layer on top
5.Who is James Hutton?
The first scientist to present a hypothesis about the Earth changing over time.
6.What is uniformitarianism?
Earth is an always-changing place; the same forces of change at work today were at work in the past

50. Paleozoic- ancient life Mesozoic- middle life Cenozoic- recent life
Short answer
7. What are the three eons of the Precambrian time?
Hadean, Archean and Proterozoic
8. What is the one eon since Precambrian time?
Phanerozoic
9. What are the three eras of the Phanerozoic eon and what are their meanings?
Paleozoic- ancient life
Mesozoic- middle life
Cenozoic- recent life