1. Since the fault displaced the sedimentary rock only, the sediment must predate the fault. From oldest to youngest we have: sedimentary; fault; basalt.

4. a) Uranium - 238 or Potassium - 40 if not older than 26 billion years (p. 628). Why 26 billion years for Potassium - 40?

b) Uranium - 235 or Potassium - 40 work best, Uranium - 238 also works but is not as precise.

c) Carbon - 14 is the only reasonable choice.

5. The amount of uranium has decreased while the amount of lead has increased. Uranium decays into lead.

7. The pebbles are older than the conglomerate in which they are located, so the conglomerate can be no older than 300 million years. Since the dike intrudes into the pre-existing conglomerate, the conglomerate is older than the dike. This places the age of the conglomerate between 200 and 300 million years.

9. Nonconformity - an unconformity in which sedimentary rocks are deposited on top of much older crystalline rock (igneous or metamorphic).

Angular unconformity - an unconformity in which the older strata dip at an angle different than that of the younger beds. (p. 626 or 643)

11. First crustal blocks survived (did not melt); first atmosphere, anaerobic atmosphere, developed; ozone layer developed; stromatolites appeared; stromatolites and certain algae developed photosynthesis; first supercontinent. (p. 630)

15. Several times during the Paleozoic the continents were flooded by shallow seas. Limestone and dolomite deposits are evidence of former seas. (p. 631)

16. Antarctica was not always located at the earth's south magnetic pole. At one time it was much closer to the equator, which allowed swamps and plant life to form.

18. a) time of crystallization of the granite.

b) time of th elast metamorphic event to affect that rock.

c) maximum age of the sandstone (the sandstone cannot be older than the mica).

20. A greater rate of spreading means warmer ocean crust. A warmer ocean crust is less dense than a cooler one, which means the crust will float higher on the lithosphere, which raises the ocean level.

23. Melting of the polar ice caps would cause the ocean level to rise. This could happen if the earth's temperature were to rise as a result of the greenhouse effect.

25. Humans not only adapt well to a changing environment, but also manipulate it as well. It is possible that humans will become extinct. Possible causes of our extinction could be natural disaster, disease or meteor impact, or unnatural, nuclear war or assimilation. Watch out for the Borg.

Have a nice Thanksgiving!