| A | B |
|---|
| How do fossils form? | Most fossils form when organisms that die become buried in sediments? |
| sediments | particles of soil and rock |
| petrified fossils | a fossil formed when minerals replace all or part of an organism |
| mold | a hollow space in sediment in the shape of an organism or part of an organism |
| What do you do with the mold? | fill it with hardened minerals to form a cast |
| cast | a copy of the shape of the organism that made the mold |
| What is the difference between a mold and a cast? | a mold is the hollow space in the sediment shaped like the organism. The cast is what is formed when minerals are put into the mold and is a copy of the organism. |
| How do you determine a fossil's age" | two ways: relative dating and radioactive dating |
