Plate Tectonics (the unifying theory in Earth Sciences) Summary Data and Questions
Definition: Theory that large segments or plates of the lithosphere move relative to one another
A. Continental Drift Hypothesis
Although Suess (1885) noted similarities of
and glaciation and named the southern super-
is credited with developing the hypothesis of Continental Drift. He suggested
a super-continent of
that formed in the Paleozoic that subsequently split apart.
1. Continental fit
2. Glacial evidence
3. Similarities of rock sequences (compositions and types including coal distribution)
4. Mountain ranges of the same age and rock type on different continents
5. Fossil evidence (Glossopteris flora, Mesosaurus, Cynognathus, Lystrosaurus)
This evidence, though persuasive, lacked a means to describe how the continents moved.
B. Plate Tectonics (move to a theory)
Evidence plus a mechanism:
a. Polar wandering
b. Magnetic reversals (striping) on the sea floor; led to idea of seafloor spreading
2. Age of ocean floor materials
3. Distribution of earthquakes
4. Distribution of volcanoes
5. Hot spot “trails”
C. Types of Plate Boundaries (see Table 2.2): Know locations and examples, types of rocks, stress
regimes, and types of geohazards
1. Divergent (spreading ridges, split apart)
2. Convergent (colliding margins)
3. Transform (strike-slip)
D. Plate Names (the big seven and there are many smaller ones), Rates of Movement (mm’s to
cm’s per year), and Mechanisms of Movement (convection cells and slab push/pull models)
1. Where do they occur and why? At what plate boundaries?
2. Types of resources: How does the previous and current distribution of plates dictate the occurrence of oil and gas,
coal, copper, gold, metals, etc.
3. Where would you look for these resources?
F. Questions for Your Consideration
1. Where are active hazardous earthquakes and volcanoes today? Where would I go to find the most exciting
2. Where are most of our resources located? What are the controls on their distribution?
3. Are there different rock types on continents and ocean floors, and if so, Why?
4. How does a hot spot reveal information to support the Plate Tectonics Theory?
G. Interior of the Earth: Composition and How do we Know and what is the significance?
1. The Earth is composed of many “layers” but you should know the main 4 including their composition, thickness
a. Lithosphere (continental and ocean) – the thin outer shell
b. Mantle - plastic
c. Outer Core - liquid
d. Inner Core – solid
2. How do we know the composition and liquid vs. solid?
Earthquake waves, seismic waves and models, nuclear explosions, meteorites