Questions Related to Geologic Time: The Dynamic Earth

Resources

• Some lecture notes about geologic time.
• A thumbnail sketch of geologic time
• A list of recommended books, many of which relate to evolution and geologic time.

1. A significant interruption in rock-forming processes results in an apparent "gap" in the rock record. One example is along the formation contact between the 1.75 billion year old Vishnu schist and the early Paleozoic strata (~550 million years old) at the bottom of the Grand Canyon. What are these discontinuities called, in general?
2. What is the name of the relative-dating principal that says that, in an undeformed sequence of sedimentary strata, the oldest layer is on the bottom?
3. What is the name of the relative-dating principal that notes that sedimentary beds are originally deposited in horizontal or near-horizontal layers?
4. What principle used in relative dating allows us to determine the age of a sedimentary rock stratum by recognizing the characteristic set of fossils contained within the stratum?
5. When a fault or a dike cuts across a layer, what principle of relative dating allows us to state that the layer must be older than the fault or dike?
6. What principle of relative dating takes note of the fact that a piece of rock that is incorporated within another rock, as in a xenolith in a granite or a pebble in a conglomerate, must be older than the rock that it is part of?
7. What eon in Earth's history extends from the coalescence of Earth from the solar nebula to the first fossils of organisms that had hard parts like bones or shells, between ~4.6 billion and 542 million years ago?
8. What eon in Earth's history extends from the age of the first fossils of organisms that had hard parts to the present, since 542 million years ago?
9. What era in Earth's history extends from the age of the first fossils of organisms that had hard parts to the greatest mass extinction in the past billion years, between 542 and 251 million years ago?
10. What era in Earth's history extends from the greatest mass extinction in the past billion years to the smaller mass extinction that finally doomed the dinosaur, between 251 and ~65 million years ago?
11. What era in Earth's history extends from the extinction of most dinosaurs to the present, since ~65 million years ago?
12. What geologic era are we living in today?
13. What geologic eon are we living in today?
14. What is a dating technique geologists use to find the age of geological material in terms of numbers of years before present?
15. What do we call the isotope that decays to produce another isotope? That is, what was the original radioactive isotope called?
16. What do we call the stable product of the radioactive decay of an isotope?
17. How much of the original radioactive material is left as a radioactive isotope after an amount of time equal to one half life has passed?
18. Do all radioactive isotopes decay at the same rate?
19. With the exception of beryllium, are the decay constants used in geological dating actually constant, or are they changed by external fields or forces?
20. What is the stable daughter product of the decay of potassium-40?
21. Under normal circumstances, how old a specimen can be dated using the carbon-14 method?
22. What does a good potassium-argon date tell you about the potassium-bearing mineral grain?
23. How far back in time do some tree-ring records extend?
24. How much time is represented by each individual varve in glacial lake sediments?
25. What is the best current scientific estimate for the age of the Earth? (see http://bearspace.baylor.edu/Vince_Cronin/www/PhysGeol/geol.time.html )
26. What is the best current scientific estimate for the age of the universe -- the time since the Big Bang?
27. About how old are the oldest fossil mammals?
28. What living non-human mammal is most closely related to modern humans?
29. Did humans evolve from any of the types of apes or monkeys or other primates that one can visit at a good zoo?
30. Approximately how old are the oldest fossils of our species, Homo sapiens?
31. On what continent did Homo sapiens evolve, as indicated by fossils and DNA evidence?

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