1. 6th Grade Science

2. © Fall 2005, Pflugerville ISD, 8th Grade Formula °C x 9/5 + 32 = °F (°F - 32) x 5/9 = °C Examples 1) Convert 37°C to Fahrenheit. 37°C x 9/5 + 32 = 98.6°F OR 37°C x 9 + 32 = 98.6°F 5 2) Convert 98.6°F to Celsius. (98.6°F - 32) x 5/9 = 37°C OR (98.6°F - 32) x 5 = 37°C 9

3. © Fall 2005, Pflugerville ISD, 8th Grade “The present is the key to the past.” -James Hutton We study the past because if we don’t, we are doomed to repeat it. But how can studying the present help us understand earth’s history? What are some processes you can see today that also occurred millions of years ago? What Do You Think?

4. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened James Hutton 1726-1797 “The present is the key to the past.” Father of modern geology

5. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Hadrian’s Wall, England Hutton knew that Hadrian’s wall was built by the Romans in historical times

6. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Hadrian’s Wall, England Only 1600 years old, the wall was already starting to weather and erode

7. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Arthur’s Seat Volcano, Edinburgh, Scotland Hutton wondered how long it would take to erode a mountain

8. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Arthur’s Seat Volcano, Edinburgh, Scotland Hutton decided that it would take millions of years, making the earth very ancient

9. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Arthur’s Seat Volcano, Edinburgh, Scotland Hutton realized that erosion and deposition have been going on for a long time

10. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened In 1788, James Hutton wrote: Theory of the Earth (a collection of his notes) notes)

11. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened James Hutton 1726-1797 In his book he described: Uniformitarianism It is the idea that the same geologic processes shaping the Earth today have been at work throughout Earth’s history.

12. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened James Hutton 1726-1797 Hutton’s views of a billion-year-old earth clashed with most scientists’ belief in catastrophism

13. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Most scientists supported catastrophism. It is the idea that all geologic change happens quickly

14. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened These scientists used huge floods, eruptions, and other catastrophes to explain rapid geologic change

15. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Catastrophism was a guiding principle for decades. Only after the work of Charles Lyell did people consider uniformitarism. 1830-1833 Lyell published 3 volumes in: –Principles of Geology –In it, he stated that change happened gradually.

16. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened Today, scientists think that sudden events are the cause of some changes in earth’s past

17. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story & Those Who Listened But they agree that the earth is old, and that most change is gradual

18. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story and Those Who First Listened Today’s Scientists realize that neither of these principles: uniformitarianism nor catastrophism account for all geologic changes. Most change is gradual, but catastrophes have occurred throughout Earth’s history.

19. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story and Those Who First Listened paleontology-science involved with the study of past life paleontologist-a scientist who studies past life What data do they study? Fossils

20. © Fall 2005, Pflugerville ISD, 8th Grade Earth’s Story and Those Who First Listened fossils-the remains of organisms preserved by geologic processes Invertebrate paleontologist-studies animals without backbones Vertebrate Paleontologist-studies animals with backbones

21. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Suppose your friend piles his stuff on his floor and never cleans his room. Under the top layer of clothes, you find a pizza box. Under this is a bunch of CDs then some homework and under this is a ham sandwich. Arrange these four layers from oldest to youngest… What Do You Think?

22. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? relative dating-determining whether an object or event is older or younger than other objects or events

23. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Grand Canyon The Principle of Superposition states that younger rocks lie over older rocks

24. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Grand Canyon The Principle of Superposition is used to find the relative ages of rock layers

25. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? James Hutton 1726-1797 Geologists can use rock layers from many locations to create a geologic column

26. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? The geologic column is an ideal sequence of rock layers that contains all known rock formations and fossils on Earth

27. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first?

28. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? The dike is the youngest feature, because the other layers were cut by it

29. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Look at page 66 Figure 3 Terms: fault-a break in the Earth’s crust along which blocks of the crust slide relative to on another intrusion-molten rock from the Earth’s interior that squeezes into existing rock and cools

30. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? folding-occurs when rock layers bend and buckle from Earth’s internal forces tilting-occurs when internal forces in the Earth slant rock layers These features are younger than the rock layers because the rock layers had to be present before the features could cut across them.

31. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? The Law of Cross-Cutting Relationships can tell geologists the relative age of a fault or intrusion

32. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Use your knowledge to order the layers, faults and intrusions in the next slide from oldest to youngest

33. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first?

34. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? If rock layers are not horizontal, something must have disturbed them after they formed.

35. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Hutton’s Unconformity An unconformity is a surface that represents a missing part of the geologic column

36. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Most unconformities form by erosion and nondeposition.

37. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? Types of unconformities: 1.disconformities-are found where part of a sequence of parallel rock is missing. This is the most common type.

38. © Fall 2005, Pflugerville ISD, 8th Grade Formation of an Unconformity 30-15 Million Years Ago Sediment is eroded from a hill and deposited in a valley

39. © Fall 2005, Pflugerville ISD, 8th Grade Formation of an Unconformity 15-5 Million Years Ago The area is uplifted and exposed to erosion, then the land surface is eroded away

40. © Fall 2005, Pflugerville ISD, 8th Grade Formation of an Unconformity 5 Million Years Ago- Present Deposition resumes Can you spot the unconformity?

41. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? 2.nonconformities-are found where horizontal sedimentary rock layers lie on top of an eroded surface of older intrusive igneous or metamorphic rock

42. © Fall 2005, Pflugerville ISD, 8th Grade Relative Dating: Which came first? 3.angular unconformities-are found between horizontal layers of sedimentary rock and layers of rock that have been tilted or folded.

43. © Fall 2005, Pflugerville ISD, 8th Grade Section 3: Absolute Dating Absolute dating-the process of establishing the age of an object by determining the number of years it has existed

44. © Fall 2005, Pflugerville ISD, 8th Grade How is this done? element-a substance that cannot be separated or broken down into simpler substances by chemical means atom-the smallest unit of an element that maintains the properties of that element isotope-atoms of the same element that have the same number of protons but a different number of neutrons

45. © Fall 2005, Pflugerville ISD, 8th Grade An atom is made of protons, neutrons, and electrons.

46. © Fall 2005, Pflugerville ISD, 8th Grade Rules In a stable atom, protons and electrons are equal.

47. © Fall 2005, Pflugerville ISD, 8th Grade Radioactive-this is what scientists call unstable isotopes Radioactive decay-a process where radioactive isotopes tend to break down into stable isotopes of the same or other elements

48. © Fall 2005, Pflugerville ISD, 8th Grade Radioactive Decay Unstable Isotope 6 protons, 8 neutrons Radioactive Decay When some unstable isotopes decay a neutron is converted into a proton. An electron is released Stable Isotope 7 protons, 7 neutrons Parent Isotope Daughter Isotope

49. © Fall 2005, Pflugerville ISD, 8th Grade What does this show you? Scientists can use it to determine an object’s age (like rocks or fossils)

50. © Fall 2005, Pflugerville ISD, 8th Grade How is this done? parent isotope-the unstable radioactive isotope daughter isotope-the stable isotope that is produced by the radioactive decay of the parent isotope

51. © Fall 2005, Pflugerville ISD, 8th Grade How do Scientists Date Rock? They compare the amount of parent material with the amount of daughter material. The more daughter material, the older the rock is. The rate of decay is constant.

52. © Fall 2005, Pflugerville ISD, 8th Grade If you know the rate of decay for a radioactive element in a rock, you can figure out the absolute age of the rock. Radiometric dating-determining the absolute age of a sample based on the ratio of parent to daughter material

53. © Fall 2005, Pflugerville ISD, 8th Grade half life-it is the time that it takes one half of a radioactive sample to decay Activity on page 70

54. © Fall 2005, Pflugerville ISD, 8th Grade Types of Radiometric Dating 1.Potassium-Argon Method Potassium-40 (parent) decays to argon (daughter) Mainly used on rocks older than 100,000 years.

55. © Fall 2005, Pflugerville ISD, 8th Grade 2.Uranium-Lead Method Uranium-238 (parent) is a radioactive material that decays to lead (daughter). The older the rock, the more lead there will be. This can be used for rocks more than 10 million years old. It is not accurate for younger rocks.

56. © Fall 2005, Pflugerville ISD, 8th Grade 3.Rubidium-Strontium Method Parent rubidium/Daughter Strontium Used to date rocks older than 10 million years.

57. © Fall 2005, Pflugerville ISD, 8th Grade 4.Carbon-14 Method Carbon is found in 3 forms: Carbon-12 & Carbon-13 (both stable) and Carbon-14 (radioactive) All of these combine with oxygen to form carbon dioxide. This is taken in by plants.

58. © Fall 2005, Pflugerville ISD, 8th Grade Once a plant dies, the amount of carbon- 14 begins to decrease as the plant decays. The ratio of carbon-14 to carbon-12 decreases with time and can be used to determine dating for things that lived within the last 50,000 years.

59. © Fall 2005, Pflugerville ISD, 8th Grade Absolute Dating When animals eat, they ingest radioactive Carbon-14

60. © Fall 2005, Pflugerville ISD, 8th Grade Absolute Dating Since C-14 has a half-life of only 5730 years, other isotopes are used to date older rocks

61. © Fall 2005, Pflugerville ISD, 8th Grade Absolute Dating James Hutton 1726-1797 The oldest rocks on Earth have been dated to 4.5 billion years, confirming Hutton’s beliefs

62. © Fall 2005, Pflugerville ISD, 8th Grade Interactive Time Scale Start on Abraham Lincoln

63. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Saber-Tooth Cat Fossil A fossil is the remains or physical evidence of an organism preserved by geologic processes

64. © Fall 2005, Pflugerville ISD, 8th Grade What happens when something dies It is either consumed by other organisms or immediately begins decaying. Being buried by sediment, slows down the decay. Hard parts like bone and shells are more resistant to decaying, so more commonly preserved.

65. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Fossil Amber with Insect Inclusions Fossilized tree sap is called amber

66. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Fossil Amber with Insect Inclusions Animals caught in amber are perfectly preserved

67. © Fall 2005, Pflugerville ISD, 8th Grade Petrifaction-a process in which minerals replace an organism’s tissues

68. © Fall 2005, Pflugerville ISD, 8th Grade Types of Petrifaction Permineralization-a process in which the pore space in an organism’s hard tissue (like bone or wood) is filled up with minerals Replacement-a process in which the organism’s tissues are completely replaced by minerals  An example, is petrified wood.

69. © Fall 2005, Pflugerville ISD, 8th Grade Fossils in Asphalt

70. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Woolly Mammoth October 1999 Scientist removed a 20,000 yr. old mammoth in Siberian tundra. Fossils of mammoths, extinct for approximately 10,000 years, have been found frozen in Arctic ice.

71. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Theropod Track A trace fossil is naturally preserved evidence of animal activity.

72. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Theropod Track This dinosaur track is located in Glen Rose, Texas, in Dinosaur Valley State Park

73. © Fall 2005, Pflugerville ISD, 8th Grade Types of Trace Fossils Burrows-shelters made by animals Coprolite-preserved animal dung

74. © Fall 2005, Pflugerville ISD, 8th Grade Things you can Learn from Fossils: how big it was, how fast it was moving, and whether they move in herds or not.

75. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Ammonite Fossil A mold is a cavity in rock where a plant or animal was buried.

76. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Ammonite Fossil A cast is an object made when sediment fills a mold and becomes rock.

77. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils

78. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Ammonite Fossil Which of these is the mold and which is the cast?

79. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Whale Bones Most animals are not buried fast enough to form fossils

80. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Whale Bones These whale bones will be broken down before they can form fossils

81. © Fall 2005, Pflugerville ISD, 8th Grade Why is the fossil record incomplete? Because most organisms never became fossils. Also, many fossils have yet to be discovered.

82. © Fall 2005, Pflugerville ISD, 8th Grade What does the fossil record reveal? A history of environmental change For example: –A marine fossil helps scientists reconstruct ancient coastlines and the depth of ancient seas. –It allows scientists to reconstruct past climates –They can determine how life has changed overtime.

83. © Fall 2005, Pflugerville ISD, 8th Grade Fossils Certain types of fossils only appear in certain layers of rock, so by dating the rock layers above and below these fossils, scientists can determine the time span that the fossil formed.

84. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Trilobite Fossil An index fossil is one found for a short time in rock layers around the world

85. © Fall 2005, Pflugerville ISD, 8th Grade Examples of an Index Fossil 1.Genus of Ammonites called Tropites These were marine mollusk similar to a modern squid. It lived in a coiled shell. They are believed to have lived 230 and 208 million years ago.

86. © Fall 2005, Pflugerville ISD, 8th Grade 2.Genus of Trilobites called Phacops Their closest relative is the horseshoe crab They are believed to have lived 400 million years ago.

87. © Fall 2005, Pflugerville ISD, 8th Grade Looking at Fossils Trilobite Fossil The trilobite (Phacops) lived for a short time 400 million years ago.

88. Time Marches On Dinosaur Quarry Visitor Center Dinosaur National Monument, Utah 1,500 bones excavated Approximately 150 million yrs. old This is 3%of the time Earth has existed.

89. One of the best places to see the Earth’s history recorded in rock layers is the: Grand Canyon

91. Colorado River The river has eroded countless layers of rock.

92. Time Marches On Humans First Arrived

93. © Fall 2005, Pflugerville ISD, 8th Grade Green River Formation These rocks are found in parts of Wyoming, Utah, and Colorado. They are thousands of meters thick. They were once a part of a system of ancient lakes. Fossils of plants and animals are common and well preserved.

94. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On The Geologic Time Scale divides Earth’s history into intervals of time.

95. © Fall 2005, Pflugerville ISD, 8th Grade Divisions of Time eon-largest divisions of geologic time There are 4 eons: 1.Hadean eon 2.Archean eon 3.Proterozoic eon 4.Phanerozoic eon-it is divided into 3 eras

96. © Fall 2005, Pflugerville ISD, 8th Grade Divisions of Time era-the second largest division of geologic time that includes two or more periods -3 eras are divided in to periods periods-the third largest division of geologic time into which eras are divided -periods are divided into epochs epochs-the fourth largest division of geologic time that is a subdivision of a period

97. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Since most fossils are from the Phanerozoic Eon, this is the eon that is given the most attention.

98. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On The Phanerozoic is actually the shortest of the four eons.

99. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Paleozoic Era 543-248 mya In the Paleozoic Era, life in the oceans, as well as all major plant groups and insects, flourished.

100. © Fall 2005, Pflugerville ISD, 8th Grade The Paleozoic era came to an end with the largest mass extinction in Earth’s history. Some scientists believe that the oceans were the cause of extinction. It killed nearly 90% of all species.

101. © Fall 2005, Pflugerville ISD, 8th Grade extinction-the death of every member of a species

102. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Mesozoic Era 248-65 mya With a mass extinction at the end of the Paleozoic, the remaining reptiles thrived

103. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Mesozoic Era 248-65 mya Known as the Age of Reptiles, birds and small mammals appeared late in the Mesozoic

104. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Cenozoic Era 65 mya- Present Mammals flourished after a mass extinction killed the dinosaurs

105. © Fall 2005, Pflugerville ISD, 8th Grade Mesozoic Era 15-20% of all species became extinct. Why? Global climate change is possible.

106. © Fall 2005, Pflugerville ISD, 8th Grade Time Marches On Cenozoic Era 65 mya- Present The Cenozoic is known as the Age of Mammals

107. © Fall 2005, Pflugerville ISD, 8th Grade Let’s Review! - 1 - What did James Hutton mean by the comment, “The present is the key to the past”?

108. © Fall 2005, Pflugerville ISD, 8th Grade Let’s Review! - 2 - How can you tell the age of rocks and fossils?

109. © Fall 2005, Pflugerville ISD, 8th Grade Let’s Review! - 3 - How is a fossil created? Describe how a geologist would use an index fossil…

110. © Fall 2005, Pflugerville ISD, 8th Grade Let’s Review! - 4 - What type of event ended both the Paleozoic and Mesozoic Eras? What geologic time period was occurring 200 million years ago?

111. © Fall 2005, Pflugerville ISD, 8th Grade Pre-AP Extensions