Reading Guide #7 -- Time
If you do nothing else, check out the Geologic Time pages from UC Berkeley.

This is an important chapter; nearly all of the concepts are important. You should read pages 165 to 185 carefully. We won't touch on the use of the magnetic timescale.

What kind of data would you interpret as relative dating and what type of data would you use as absolute dating?

Be sure to look hard at the diagrams illustrating the unconformaties. How do you interpret what went on during those periods of "missing time"?

What is the difference between a rock-stratigraphic unit, a time-stratigraphic unit, and a time unit?

Memorize the Periods and Eras on fig 6.10 (the geologic time scale; it will be found in any book), as well as the absolute ages between the Eras.

Absolute time.

What is an isotope? How do atoms of one particular element transform into atoms of another element? Be able to identify and figure out atomic number and mass number. Understand Beta decay in detail; be able to draw a picture of it.

Understand the exponential rate of decay. I'm not sure the book uses the word "exponential", but that's what it's called. How is exponential growth or decay different from geometric growth or decay, i.e., a straight line on a graph?

What sort of rocks are appropriate for K-Ar and 14C dating? This is sort of a trick question.
Watch out for the derivation of equations on page 181. Although this way works fine, it is non-traditional and is not what you will find if you revisit these topics anywhere else. I will give the more traditional approach in class. I think this difference resulted in a misguided attempt to simplify these equations and remove e, the Natural Logarithmic Base. I don't think this was wise as it confuses the issue and limits the applications. It would be fine with me if you did not read the right-hand column on page 181 and only listened to my explanation in class.

See if you can follow the geologic history in figure 6.15. On that figure, why does the bottom of te Eocene unit (just above the unconfomity) have both green and brown rocks?
OK, you're done. How is this stuff going? E-mail me your comments.