earth history

5. break in the Earth's crust
8. minerals stick the grains of sediment together - just like cement
10. an animal without backbone
13. a long and distinct period of history with a particular feature or characteristic.
14. radioactive elements occur naturally in igneous rock
15. this is the number of years since a rock formed, it is hard to know the number exactly but scientists can trace it to date range

1. the surface where new rock meets a much older rock surface
2. lava that hardens on the surface of earth
3. a long cylinder of glacial ice recovered by drilling through glaciers
4. organisms are preserved in ice, amber or tar
6. an animal with backbone
7. the age of rocks compared to other rocks, this comparison uses words like older or younger
9. states that horizontal sedimentary rock layers, the oldest rock are at the bottom and each higher layer is younger than the layer below it
11. a solid copy of the shape of an organism
12. the amount of time it takes for half of the atoms in a radioactive element to decay or be stable