Lecture 12 Reading Guide -- Global Tectonics

This is a pretty good chapter and we cover most of the material in it.

The first section is about Continental Drift and why the geological community did not believe Wegener. What was Wegener's evidence and why didn't people believe him? What is the difference between Continental Drift and Plate Tectonics? What is Apparent Polar Wander? Why is the word "Apparent" included in this term?

What was the role of paleomagnetism in the development of Plate Tectonic theory? Why is it important that the reversals have happenned at random intervals in the geologic past? Think about it this way: how would we use the paleomagnetic time scale as a geochronologic tool

Stare at table 16.1. While I didn't reporoduce this table exactly in lecture, we have talked about many of these concepts throughout the quarter. Much of this stuff should be familiar to you and easily learned.

We've talked about much of the material from 467-476 at various time in the quarter. It should be mostly review for you here, but read it to make sure.

New material begins again on page 476. How are volcanic seamount chains used to measure absolute plate motion? What is "absolute" plate motion actually relative to?

The section on Cause of Plate Tectonics beginning on page 478 is important. We really don't know how mantle convection drives plate tectonics. One thing we do know is that the absolute motion of the plates is towards their trenches and that there is a correlation between the amount of trench a plate has and its velocity. Thus, the Pacific Plate is one of the fastest plates. Figure 16.17 shows three ideas on what processes might drive plate tectonics.

Pages 480-493 talk about mountain building processes. What is a continental Shield? Note how the orogens i fig 16.18 crop out in elongated belts. Why is this? Why is the Superior craton and Penokean otogen cut off by the Grenville Province in fig 16.18?

Continuing on pp. 482-483, how do active continental margins differ from passive continental margins?

On pages 483-493, What do continental collisions have to do with accreted terranes? Note that every accreted terrane does not have to involve a continental collision. How did the San Andreas Fault evolve? What was happenning before 29 million years ago? Why do the orogenic belts on the east coast and west coast of North America look so different? Which coast is most simlar to the Alps in Europe?