| A | B |
|---|
| fossil | the remains or traces of past life, found in sedimentary rock |
| mold | the hollow space that is left when sediment hardens around the remains of an organism and the remains then dissolve |
| cast | a fossil formed when dissolved minerals fill a mold and harden |
| index fossil | a fossil of an organism that lived in many places around the world for a short period of time; it can help scientists find the age of a rock layer |
| paleontology | the study of fossils |
| organisms | living things |
| continental drift | the theory that continents have been drifting apart for millions of years |
| Pangea | the huge land mass that made up early Earth |
| petrified | harden rocklike fossil |
