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Fall 2005, Pflugerville ISD, 8th Grade 8th Grade Science Slide 2 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 Chapter 16- The Rock & Fossil Record Section 1: Earths Story & Those Who First Listened Section 2: When on Earth? Section 3: Looking at Fossils Section 4: Time Marches On Slide 3 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 The present is the key to the past. -James Hutton We study the past because if we dont, we are doomed to repeat it. But how can studying the present help us understand earths history? What are some processes you can see today that also occurred millions of years ago? What Do You Think? Slide 4 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened James Hutton 1726-1797 The present is the key to the past. Father of modern geology Slide 5 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Hadrians Wall, England Hutton knew that Hadrians wall was built by the Romans in historical times Slide 6 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Hadrians Wall, England Only 1600 years old, the wall was already starting to weather and erode Slide 7 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Arthurs Seat Volcano, Edinburgh, Scotland Hutton wondered how long it would take to erode a mountain Slide 8 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Arthurs Seat Volcano, Edinburgh, Scotland Hutton decided that it would take millions of years, making the earth very ancient Slide 9 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Arthurs Seat Volcano, Edinburgh, Scotland Hutton realized that erosion and deposition have been going on for a long time Slide 10 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened James Hutton 1726-1797 Uniformitarianism is Huttons belief that geologic processes are uniform and do not change over time Slide 11 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened James Hutton 1726-1797 Huttons views of a billion-year-old earth clashed with most scientists belief in catastrophism Slide 12 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Most scientists supported catastrophism, the idea that all geologic change happens quickly Slide 13 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened These scientists used huge floods, eruptions and catastrophes to explain rapid geologic change Slide 14 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened Today, scientists think that sudden events are the cause of some changes in earths past Slide 15 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Earths Story & Those Who Listened But they agree that the earth is billions of years old, and that most change is gradual Slide 16 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? 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? Slide 17 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? Grand Canyon The Principle of Superposition states that younger rocks lie over older rocks Slide 18 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? Grand Canyon The Principle of Superposition is used to find the relative ages of rock layers Slide 19 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? The Law of Cross-Cutting Relationships can tell geologists the relative age of a fault or intrusion Slide 20 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? The dike is the youngest feature, because the other layers were cut by it Slide 21 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Relative Dating Use your knowledge to order the layers, faults and intrusions in the next slide from oldest to youngest Slide 22 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Relative Dating Slide 23 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Relative Dating James Hutton 1726-1797 Geologists can use rock layers from many locations to create a geologic column Slide 24 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Relative Dating Slide 25 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Relative Dating The geologic column is an ideal sequence of rock layers that contains all known rock formations and fossils on Earth Slide 26 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 When on Earth? Huttons Unconformity An unconformity is a surface that represents a missing part of the geologic column Slide 27 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Formation of an Unconformity 30-15 Million Years Ago Sediment is eroded from a hill and deposited in a valley Slide 28 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Formation of an Unconformity 15-5 Million Years Ago The area is uplifted and exposed to erosion, then the land surface is eroded away Slide 29 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Formation of an Unconformity 5 Million Years Ago- Present Deposition resumes Can you spot the unconformity? Slide 30 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Absolute Dating When animals eat, they ingest radioactive Carbon-14 Slide 31 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Absolute Dating Carbon-14 decays into Nitrogen-14 Carbon-14 Nitrogen-14 Slide 32 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Absolute Dating By comparing the amount of C-14 to N-14, geologists can calculate the age of a fossil Slide 33 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 2 Absolute Dating Since C-14 has a half-life of only 5730 years, other isotopes are used to date older rocks Slide 34 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 1 Absolute Dating James Hutton 1726-1797 The oldest rocks on Earth have been dated to 4.5 billion years, confirming Huttons beliefs Slide 35 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Imagine that a geologist 65 million years from now has unearthed fossils of your life. What would she find? What Do You Think? Slide 36 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Saber-Tooth Cat Fossil A fossil is the remains or physical evidence of an organism preserved by geologic processes Slide 37 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Fossil Amber with Insect Inclusions Fossilized tree sap is called amber Slide 38 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Fossil Amber with Insect Inclusions Animals caught in amber are perfectly preserved Slide 39 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Woolly Mammoth Fossils of mammoths, extinct for 12,000 years, have been found frozen in Arctic ice Slide 40 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Theropod Track A trace fossil is naturally preserved evidence of animal activity Slide 41 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Theropod Track This dinosaur track is located in Glen Rose, Texas, in Dinosaur Valley State Park Slide 42 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Ammonite Fossil A mold is a cavity in rock where a plant or animal was buried Slide 43 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Ammonite Fossil A cast is an object made when sediment fills a mold and becomes rock Slide 44 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Slide 45 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Ammonite Fossil Which of these is the mold and which is the cast? Slide 46 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Whale Bones Most animals are not buried fast enough to form fossils Slide 47 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Whale Bones These whale bones will be broken down before they can form fossils Slide 48 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Trilobite Fossil The trilobite Phacops lived for a short time 400 million years ago Slide 49 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Trilobite Fossil An index fossil is one found for a short time in rock layers around the world Slide 50 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 3 Looking at Fossils Trilobite Fossil If Phacops is found in a rock layer, the rock must be about 400 million years old Slide 51 Fall 2005, Pflugerville ISD, 8th GradeUnit 4 : Chapter 16 : Section 4 Time Marches On If the history of

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