Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
P337\Section 4 Geologic Time Scale • 1a How long ago did the Earth form? • 4.6 billion years ago • Summarize the process by which scientists determined the age of Earth. • Scientists studies rock layers and fossils worldwide and placed Earth’s rock layers in order by relative age. Later, radioactive dating helped them determine the absolute ages of the divisions. • What are the basic units into which the geologic time scale is divided? • The geologic time scale is divided into eras and periods. • Study figure 14. (p336) Which major division of time was the longest? • Precambrian • When did it begin? • 4.6 BYA • When did it end? • 544 MYA • Place the following in the correct order from earliest to latest: Tertiary, Jurassic, Quaternary, Triassic, and Cretaceous. • Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary Section 5 Early Earth p. 341e • 1a How long ago did the Earth form? • The Earth formed about 4.6 billion years ago • Summarize the process by which scientists determined the age of the Earth. • Scientists used radioactive dating of rocks from Earth and moon to determine the age of the Earth. • What physical features formed during Earth’s first several hundred million years? • Oceans, the atmosphere, and continents were formed. • How did volcanic eruptions and comets change early Earth? • Volcanic eruptions released carbon dioxide into the atmosphere, and comets released water vapor. • What caused water erosion to begin on Earth’s surface? • Rain • What do scientists think were the first organisms to evolve on Earth? • Organisms similar to our present day bacteria were probably the first life forms. • How would Earth’s atmosphere be different if organisms capable of photosynthesis had not evolved? • The Earth’s atmosphere would have little or no oxygen. A by-product of photosynthesis is oxygen.