INTRODUCTION.

In this segment we will discuss the basic principles of plate tectonic theory. Herein is a list of topics to be discussed in class with important terms underlined. I will provide you with definitions for these terms in class and also on this web page (as soon as I fix my office computer) under "Plate tectonic terms".

TOPICS.

A. Lithospheric plates

What are they?

How thick are they?

How do they move?

B. Plate boundaries

1. Divergent plate boundaries , oceanic ridges, and sea floor spreading

-Mid-Atlantic Ridge

-African rift valley

-Red Sea and Gulf of Aden

2. Convergent plate boundaries, trenches, and subduction

a. oceanic-oceanic convergent boundaries and volcanic arcs

-Japan

b. oceanic-continental convergent boundaries

-Southern American/Andean margin

- NW U.S. (Washington-Oregon)

c. continental- continental convergent boundaries

-Himalayans

3. Transform plate boundaries

a. ridges to ridges

b. ridges to trenches

c. trenches to trenches

d. Case study: San Andreas transform fault

C. Plate Movement

1. Determining direction

2. Determining rate of movement

D. Hot Spots

-Hawaiian Island-Emperor Seamounts

E. Driving Forces

1. mantle thermal convection

2. slab-pull

3. ridge-push

F. Active and Passive Margins

In Parts I-IV we have discussed:

continental drift,

characteristics of the oceans and continents which must be explained by any theory accounting for the dynamic nature of the Earth's crust, and

the basic principles of plate tectonics

As you review your lecture notes and the text, I want you to go back and review the characteristics of the oceans and continents which must be explained by any theory accounting for the dynamic nature of the Earth's crust.

How can these characteristics be explained by plate tectonic theory?

For example:

Why is sediment thinner on ocean ridges and thickens away from the ridge?

Why is the crust of ocean ridges young and progressively older away from the ridge?

How does plate tectonics explain the global distribution of earthquakes?

How does plate tectonics explain the global distribution of volcanoes?

What is the explanation for linear arrangements of islands and seamounts away from plate boundaries?

What accounts for the elevation of ridges and the deepening of oceanic crust away from ridges?

Why are volcanic arcs located near trenches?

Why do the passive margins of Atlantic bordering continents have thick sediment accumulations and little seismic and volcanic activity?

Why is all oceanic crust so young when compared to the average age of continental crust?

Why are magnetic anomalies parallel to ocean ridge crests?

If you take the time to answer such questions, you will see that plate tectonic theory does account for the observations we initially made about the oceans and continents. In doing so, it passes the initial test of any hypothesis.

Take the time to answer the questions above and other similar questions (of your own) which link observations with the theory of explanation. Such questions would be excellent test questions. One or more of the above, will be on the exam!