Man's physical universe

xanabras

THE HISTORY OF THE EARTH 177

6. How would you account for the rather sudden demise of the dinosaurs?

7. If each minute should represent 1,000,000 years, how long has the earth been

in existence?

How long has man been in existence?

8. In the place where your home town is located, what was the probable condition

of the earth's surface during (a) Ordovician, (b) Devonian, (c) Permian,

(d) Jurassic time?

9. What evidence can you give to prove that the earth's surface has undergone

many changes?

10. Upon what basis are divisions in geological time made?

11. At what periods was a large portion of North America under water?

12. Of what value is the study of fossils to the scientist?

13. How does the paleontologist identify rock strata?