WEARING AWAY THE EARTH'S SURFACE 



201 



for some of them are not now found alive anywhere 

 un the earth. 



From a study of rocks and fossils the following 

 conclusions have been drawn. 



1. Living things have been on the earth a long 

 time, perhaps more than five hundred million years. 



2. Simple living things such as one-celled plants 

 and animals came into existence first. 



3. Life on the earth has been slowly changing. As 

 time goes on many forms of life die out and are re- 

 placed by more and more complex forms. 



Exercise. In your notebook 1 make a list of facts to 

 support each of the following general statements. 

 The earth is very old. 



Scientists are not sure just how the earth was formed. 

 The earth has not always been as it is today. 

 Scientists understand how the various types of rocks 

 were formed. 



Scientists are able to tell with considerably accuracy 

 the kinds of climate prevalent during past ages of the 

 earth. 



REFERENCES FOR FURTHER STUDY 

 Texts 



Caldwell and Curtis, Science for Today, Chap. 19 

 Clement, Collister, and Thurston, Our Surroundings, Chap. 



21 

 Hunter and Whitman, My Own Science Problems, Unit 9; 



Science in Our Social Life, Unit 10 

 Lake, Harley, and Welton, Exploring the World of Science, 



Chap. 13 

 Pieper and Beauchamp, Everyday Problems in Science, Unit 



2 

 Powers, Neuner, and Bruner, This Changing World, Chaps. 



16, 17; Man's Control of His Environment, Chap. 32 

 Skilling, Tours through the World of Science, Tours 1, 2 

 Van Buskirk and Smith, The Science of Everyday Life, 



Chap. 7 



Watkins and Bedell, General Science for Today, Unit 3 

 Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 7 (part) 



Wood and Carpenter, Our Environment: Iff Relation to Us, 

 Topic 4; Our Environment: How We Control It, Topic 

 13 

 'Set workbook, p. 74. 



Special references 



Fabre, This Earth of Ours 



Grew, The Romance of Modern Geology 



Hawksworth, The Strange Adventures of a Pebble 



Loomis, Field Book of Common Rocks and Minerals 



Lucas, Animals of the Past 



Thomson, Outline of Science 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. The concept that the earth is very old. 



2. A knowledge of the various classes of rocks and 

 how they are formed. 



3. Skill in identifying common rocks and minerals. 



4. The habit of observing the nature and types of rock 

 in your community. 



TEST OF MASTERY OF THE TOPIC 



In your notebook complete the statements, answer the 

 questions, and comply with the instructions. 



1. Marble is a rock. 



2. Limestone is a rock. 



3. Granite is a rock. 



4. How are igneous rocks formed? 



5. How were metamorphic rocks formed? . 



6. How were stratified rocks formed ? 



Select the word or group of words which most satisfac- 

 torily completes each of the following statements. 



7. Rocks formed of sediment deposited by water are called 

 metamorphic igneous sedimentary marble 

 conglomerate 



8. Rocks formed by heat and pressure are called 

 igneous sedimentary conglomerate metamor- 

 phic limestone 



9. Rocks formed from hot molten matter are called 

 conglomerate metamorphic igneous limestone 

 sedimentary 



10. An example of a sedimentary rock is 

 limestone granite marble quartz slate 



11. Which of the following is a metamorphic rock? 

 granite marble limestone quartz 



12. Which of the following is an igneous rock? 

 granite shale coal marble limestone 



13. The remains or imprint of a living thing in rock is 

 called mineral erosion fossil humus shale 



14. The age of the earth is believed to be 

 billions of years millions of years 

 thousands of years hundreds of years 



TOPIC 2. THE WEARING AWAY OF THE EARTH'S 



SUGGESTIONS AND HELPS FOR STUDY 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What are the agents of mechanical weather- 

 ing? 



2. What are the agents of chemical weathering? 



3. What are the agents of erosion? 



4. What are the dangers of too much erosion? 



5. What internal agencies change the earth's 

 surface ? 



1. Read the problems carefully and be certain that 

 you understand them before you begin your reading 

 and .investigations. 



2. In working out the problems, make a careful 

 study of each of the following: ice, wind, water, tem- 

 perature changes, plants, animals. 



3. Make personal observations and study of a re- 

 gion which is not being eroded very much, and con- 

 trast it with a region which is being eroded rapidly. 



