15.9: Understanding Earth's History- Challenge 2
- Page ID
- 5907
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- 1. If the same sedimentary rock layer is found on either side of a valley, ___.
- the rocks formed in the same environment, and the valley was cut into the rock later
- 2. The principle of original horizontality states that ___.
- sediments are deposited in horizontal layers
- 3. If a fault cuts through an entire sequence of rock layers, the fault is ___ than the rock sequence.
- younger
- 4. If rock P cuts across rock Q, than rock P is ___ than rock Q.
- younger
- 5. The relative age of a rock is ___.
- the age of the rock relative to other rocks and geologic structures
- 6. A key bed must ___.
- be very distinctive
- 7. Fossils of microorganisms are called ___.
- microfossils
- 8. The thin layer of clay with a high concentration of iridium correlates with ___.
- the extinction of the dinosaurs and other organisms at the end of the Cretaceous
- 10. If Earth's history is condensed into one calendar year, dinosaurs appear ___.
- in mid-December
- 11. The geologic time scale was originally based ___.
- entirely on relative dating
- 12. We live in the Holocene Epoch, which is encompassed by ___.
- the Phanerozoic Eon, the Cenozoic Era, and the Quaternary Period