THE RELATIVE AGES OF FOSSILS

1. Vocabulary Foldable XIV THE RELATIVE AGES OF FOSSILS

2. The preserved remains, trace, or imprint of an ancient organism FOSSILS

3. The actual age of a rock or fossil ABSOLUTE AGE

4. The age of an object or event in comparison to another object or event RELATIVE AGE

5. Small, loose pieces of rock SEDIMENT

6. Rock formed from layers of compacted sediments SEDIMENTARY ROCK

7. The principle that in undisturbed sedimentary rock layers, older layers of rock will lie beneath younger layers LAW OF SUPERPOSITION

8. The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

9. Fossils help scientists learn about organisms from the past Scientists use rocks and fossils to try to date events, or figure out when in history things happened Absolute age is the actual age of a rock or fossil Relative age describes the age of an object or event in comparison to another object or event, for example you are younger than your parents The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

10. Scientists use the positions or rock layers to determine the relative ages of the rocks They use this information to figure out the relative ages of the fossils in those rocks This helps them figure out the ages of other rock layers that contain the same kind of fossils Fossils and the law of superposition have allowed scientists to determine the order in which many organisms evolved The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

11. Most fossils are found in rocks that form slowly in many layers Fossils can form when layers of sediment build up over a dead organism Over time, layers of sediment can compact and cement together, turning into rock Rock formed from layers of compacted sediment is called sedimentary rock The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

12. As the sediment turns to rock, parts or traces of any organisms that are buried in the sediment can be preserved within the rock Fossils are most likely to form in places where sediment piles up quickly Fossils provide a great deal of evidence about the order in which organisms evolved The position of fossils within rock layers has helped scientists to construct the geologic time scale The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

13. When layered rock is not disturbed, the lowest rock layers are the oldest Higher rock layers are progressively younger The law of superposition states that in undisturbed sedimentary rock layers, older layers of rock will lie beneath younger layers of rock This idea makes sense, because the older sediments must be laid down before the younger ones can pile up on them The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

14. Since the lowest rock layers are oldest, they contain the oldest fossils The fossils in higher layers get younger as you go up the layers Fossils in the tip layer are from organisms that lived most recently The Relative Ages of Fossils TCAP Lesson 10 NOTES P. 31

15. Scientists find that fossils are abundant in many rock layers of a similar age. They also find that the number of fossils suddenly decreased in the rocks right above those layers. Which of the following could explain that decrease? a. the high success rate of the organism b. the end of an ice age c. gradual warming of the climate d. the start of an ice age The Relative Ages of Fossils TCAP Lesson 10 HwP. 32

16. 2. Which of the following is an example of a relative age? a. 30,00 years ago b. in 300 CE c. in the beginning of the Jurassic period d. after the extinction of Tyrannosaurus rex The Relative Ages of Fossils TCAP Lesson 10 HW P. 32

17. 3. A dig in a desert finds a large number of fossils of marine plants and animals more than 200 million years old. What is the MOST LIKELY explanation for this finding? a. The area was once covered by an ocean b. The area was a dumping ground for humans that are sea creatures c. The area used to receive large amounts of rainfall d. The area was once covered by a glacier The Relative Ages of Fossils TCAP Lesson 10 HW P. 32