1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu CH. 9 - EARTH’S HISTORY Students know the evidence from geological studies of Earth and other planets suggest that the early Earth was very different from Earth today. Students know how the composition of Earth’s atmosphere has evolved over geologic time and know the effect of outgassing, the variations of carbon dioxide concentration, and the origin of atmospheric oxygen.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 The Geologic Column An arrangement of rock layers that is based on the relative ages of the rocks. Rock layers are distinguished by the types of rock the layers are made of and by the kinds of fossils the layers contain. The geologic time scale outlines the development of Earth and of life on Earth. Fossils in the upper layers resemble modern plants and animals.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 The Geologic Column, continued Using a Geologic Column To determine the layer’s age, scientists compare a given rock layer with a similar layer in a geologic column that contains the same fossils or that has the same relative position. If the two layers match, they likely formed at about the same time.

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 Divisions of Geologic Time The geologic history of Earth is marked by major changes in Earth’s surface, climate, and types of organisms.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 Divisions of Geologic Time, continued

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 Divisions of Geologic Time, continued Eons and Eras The largest unit of geologic unit of time is an eon. –Four eons: the Hadean eon, the Archean eon, the Proterozoic eon, and the Phanerozoic eon. The first three eons are part of a time interval commonly known as Precambrian Time - is a 4 billion year interval containing most of Earth’s history.

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 Divisions of Geologic Time, continued Eons and Eras era a unit of geologic time that includes two or more periods The first era of the Phanerozoic eon was the Paleozoic Era, which lasted 292 million years.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Geologic Time Chapter 9 Divisions of Geologic Time, continued Eons and Eras period a unit of geologic time that is longer than an epoch but shorter than an era epoch a subdivision of geologic time that is longer than an age but shorter than a period.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Precambrian Time and the Paleozoic Era Chapter 9 Precambrian Time Precambrian time the interval of time in the geologic time scale from Earth’s formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million years ago. –which makes up 88% of Earth’s history.

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Precambrian Time and the Paleozoic Era Chapter 9 Precambrian Time, continued

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Precambrian Time and the Paleozoic Era Chapter 9 Precambrian Time, continued Most Precambrian rocks have been so severely deformed and altered by tectonic activity that the original order of rock layers is rarely identifiable.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Precambrian Time and the Paleozoic Era Chapter 9 The Paleozoic Era Paleozoic Era lasted from 542 million to 251 million years ago. rocks hold an abundant fossil record. –plant and animal species on Earth increased dramatically.

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 The Mesozoic and Cenozoic Eras Chapter 9 The Mesozoic Era mass extinction an episode during which large numbers of species become extinct Mesozoic Era the geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles. –Pangaea broke into smaller continents, and the climate was warm and humid. –Lizards, turtles, snakes and dinosaurs flourished during this era.

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 The Mesozoic and Cenozoic Eras Chapter 9 The Mesozoic Era, continued

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 The Mesozoic and Cenozoic Eras Chapter 9 The Mesozoic Era, continued The Triassic Period The Mesozoic Era is known as the Age of Reptiles and is divided into three periods: the Triassic, the Jurassic, and the Cretaceous Periods. The Triassic period marked the appearance of dinosaurs. Most dinosaurs were about 4 m to 5 m long and moved very quickly.

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 The Mesozoic and Cenozoic Eras Chapter 9 The Mesozoic Era, continued The Cretaceous Period The earliest flowering plants, or angiosperms, appeared during this period. Later, trees such as maples, oaks, and walnuts became abundant.

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 The Mesozoic and Cenozoic Eras Chapter 9 The Cenozoic Era Cenozoic Era the current geologic era, which began 65.5 million years ago; also called the Age of Mammals During the Cenozoic Era, dramatic changes in climate have occurred. As temperatures decreased during the ice ages, new species that were adapted to life in cooler climates appeared. Mammals became the dominant life-form and underwent many changes.

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 9 Maps in Action Fossil Evidence for Gondwanaland Maps In Action

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Geologic Time Scale Chapter 9

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Similar Skeletal Structures of Mammals Chapter 9

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Precambrian Time and the Paleozoic Era Chapter 9

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Mesozoic and Cenozoic Era Chapter 9

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Fossil Evidence for Gondwanaland Chapter 9