Earth History

2. the theory that the continents have moved over time
4. the type of rock that is made of hardened sediment where fossils are found
8. a fossil that is a copy of an organisms shape, formed when minerals seep into mold
9. the age of a rock given as the number of years since the rock formed
10. a fossil in which minerals replace all or part of an organisms
12. a record of the geological events and life forms in Earth's history
16. a place where an old, eroded rock surface is in contact with a newer rock layer
19. a type of fossil consisting of an extremely thin coating of carbon on rock
21. the geological principle that states in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it
23. the length of time needed for half of the atoms of a sample of a radioactive isotope to decay

1. fossils of widely distributed organisms that lived during only one short period
3. the age of rock compared to the ages of rock layers
5. the breakdown of a radioactive element, releasing particles and energy
6. a break or crack in Earth's lithosphere along which the rocks move
7. a scientist who studies fossils to learn about organisms that lived long ago
11. a fossil formed when an organism buried in sediment dissolves leaving a hollow area
13. describes a type of organisms that no longer exists anywhere on Earth
14. an igneous rock layer formed when magma hardens beneath Earth's surface
15. a type of fossil that provides evidence of the activities of ancient organisms
17. an igneous rock layer formed when lava flows onto Earth's surface and hardens
18. one of those three long untits of geologic time between the Precambrian and the present
20. the preserved remains or traces of living things
22. one of the units of geologic time into which geologist divide eras