1. Relative dating is dating based on the order of occurrence or the sequence of
events and absolute dating is based on radiometric measurements.
2. Assumption of steady rate of deposition. The geologic records must be complete
and the accumulation rates known or the age cannot be determined.
3. Lord Kelvin assumed that the earth cooled at a constant rate and made his
calculations based on the amount of time it would take to get the current surface
temperature and gradient. His basic flaw was that he didn’t know that radioactive
decay kept resupplying the heat. At the time, the main arguments were between
Biblical literalists and scientists. Even though he didn’t have knowledge of
radiometric dating, Kelvin’s date was still old enough to anger the Biblical
literalists. If it hadn’t been discovered, the assumed age of the earth would
probably much less than it is today.
4. Yes, the principles of relative dating could be used on Mars with the exception of
fossil succession.
5. The difference between a sill and a lava flow is that a lava flow would occur at
the surface so it would be younger than the layers below it. A sill would be an
intrusion and would place a younger rock in the middle of an older rock.
6. At a disconformity, there will be a large difference in the fossils that are found in
the older and younger strata. At a nonconformity, there will be fragments of the
older rock included in the younger overlying rock layers. If it is an intrusion as
opposed to a nonconformity, there will be inclusions of the overlying rock
included in the intrusion (the intrusion would be younger than the overlying rock).
7. Radiometric dating works best in igneous rocks because they are unaltered by
deformation, weathering, or metamorphism. Sedimentary rocks would yield a
date for the age of the original parent rock from which the mineral was derived
rather than the age of the sedimentary rock. A metamorphic rock would yield the
age that the rock was altered and not originally formed.
8. It is possible that the different methods are dating different events. That is that
one isotope pair dated the age that the volcano that produced the lava that became
the igneous rock and the other method dated the age that the rock crystallized
9. C-14 is used to date materials that are carbon-based, meaning things that were
once alive.
10. The parent material, the daughter material, the ½ life, and the ratio of the two
materials.
1. 1/64th or 1.5%
2. 5 ½ lives
3. Short term changes cannot always be extrapolated to long term trends to predict
what the earth will look like. Short term weather patterns can be affected by
things like volcanic explosions and while this may result in a short term decrease
in world temperatures, the long term trend of an increase in temperature will not
change. As the plates continue to move, the ocean currents will be affected as
well as things like weather patterns that are dependent on the ocean currents. The
one thing that can affect the rates in a manner that no one can predict is the human
influence on things like climate.