Earth Science

3. / The time it takes for half of the atoms in a radioactive sample to decompose
4. / Atoms of the same element with different numbers of neutrons.
5. / Measurement refers only to the order in which events occurred
6. / Correlated rocks from many localities around the world.
13. / Matched rocks of the same age from different localities
14. / Tectonic activity titled older sedimentary rock layers, & erosion planed the off, before younger sediment accumulated
16. / Thin, widespread sedimentary layer that deposited rapidly.
18. / This Era is when mammals and grasses became abundant.
19. / States that life forms have changed throughout geologic time
20. / Eras that are subdivided

1. / Eons divide into ______
2. / This Era contains fossils of early life forms, such as invertebrates, fishes, amphibians, reptiles & ferns
7. / A nearly complete composite record of geologic time
8. / Unconformity in which sedimentary rocks lie on igneous rocks.
9. Dating / The process of determining the absolute age of rocks, minerals & fossils.
10. / Hadean, Archean, Proterozioc Eons are commonly referred to as this
11. / Sedimentary rocks deposited without interruption
12. / Age in years
15. / Remains and other traces of prehistoric life preserved in rocks.
17. / The largest time units