Science

2. the number of years that have passed since the rock formed.
5. the atoms of one element break down to form atoms of another element
6. The preserved remains of living things
8. present into three long units of time
9. Geologists divide the time between the Precambrian and
11. a record of the geologic events and the evolution of life forms as shown in the rock and fossil records.
12. have scaly skin and lay eggs that have tough, leathery shells.
14. a vertebrate that controls its own bodytemperature and feeds milk to its young.
15. animals without backbones
16. dating to determine the absolute ages of rocks

1. Eras are subdivided into units of geologic time
3. a gap in the geologic record
4. to determine the relative ages of sedimentary ages of rock layers.
7. an animal with a backbone
10. an event during which many types of living things became extinct at the same time.
12. a rock Is the number of years that have passed since the rock formed.
13. an animal that lives part of its life on land and part of its life in water