528 



The Earth and Its Inhabitants Change unit x 



Fig. 478 This painting by Charles R. Knight shows an ancient ground slot]} stuck in 

 a tar pool. The saber-toothed tiger appears ready to step in. This is one way in which 



fossils for?//. (AMERICAN MUSEUM. OF NATURAL HISTORY) 



Insects crawling on the trunks of ever- 

 greens ages ago were trapped in the sticky 

 resin which oozed from these trees. 

 Through the ages the resin hardened 

 into amber; the insect caught in the cen- 

 ter of the mass remained preserved and 

 unchanged. Enormous numbers of such 

 fossils have been found in the amber near 

 the Baltic sea. 



From the icy bogs of northern Siberia, 

 there have been recovered several bodies 

 of mammoths, a type of woolly elephant 

 no longer in existence today. The ani- 

 mals had been so perfectly preserved 

 that the flesh could still be eaten. In the 

 mouth of one mammoth was found the 

 unchewed grass which it had cropped 

 supposedly just before it fell into an ice 

 crevasse (crack) thousands of years ago! 

 Of course, fossils formed in this way are 

 rare. You will find it interesting to study 

 examples of different types of fossils. See 

 Exercise 7. 



The word fossil is difficult to define. 

 It means the remains of animal or plant 

 life from bygone ages preserved in any 

 form w hatever; it may be nothing more 

 than an imprint of an animal or plant. 



Fossil hunting. Since fossils were 

 formed in earlier eras you would expect 

 them to be buried deep in the earth, cov- 

 ered by the more recently formed sedi- 

 mentary rock. No one knows what great 

 fossil treasures may lie hidden beyond 

 man's reach. But fortunately there are 

 several ways in which fossils may become 

 exposed. Sometimes a river cuts a deep 

 channel through sedimentary rock as in 

 the Grand Canyon of the Colorado. Thus 

 walls of rock to a depth of thousands of 

 feet are laid bare. Frequently, where a 

 mountain chain has been uplifted, strata 

 of rock have been broken through and 

 the edges upturned and raised far above 

 sea level. In this way strata millions of 

 years old and thousands of feet deep are 

 brought to the surface. Thus fossils can 

 be found in many parts of our countrv, 

 in such large numbers that in some re- 

 gions any boy or girl may discover them. 

 Also in mining operations where men 

 sink shafts into the earth, they find fos- 

 sils which are buried relatively near the 

 surface. 



Frequently the location of fossil beds 

 is known or suspected, as in the Gobi 



