Across |
3. | the geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it |
7. | a scientist who studies fossil to learn about organisms that lived long ago |
9. | the process of determining the age of an object using half-life of one or more radioactive isotopes |
10. | a place where an old, eroded rock surface is in contact with a newer rock layer |
11. | the process by which all the different kinds of living things have changed over time |
16. | a type of fossil that provides evidence of the activities of ancient organisms |
17. | a break or crack in Earth’s lithosphere along which rocks move |
18. | one of the units of geologic time into which geologists divide eras |
19. | the type of rock that is made of hardened sediment |
20. | a fossil that is a copy of an organism’s shape formed when minerals seep into a mold |
21. | the age of a rock compared to the ages of rock layers |
23. | fossils of widely distributed organisms that lived only during a short period |