GSC 111 Lecture Notes - Lecture 7: Plate Tectonics, Continental Crust, Seismic Wave
13 Jan 2017
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Plate Tectonics
1. Compositional boundaries of the Earth
a. Core
i. Rich in iron and nickel
ii. Very dense
b. Mantle
i. Less dense than the core
ii. Rich in magnesium-iron silicates
c. Crust
i. Continental crust
1. Mostly granitic-type rocks
2. 35 km thick
ii. Oceanic crust
1. Mostly basalt type rocks
2. 7 km thick
2. Seismic waves and Earth’s structure
a. P-waves: “push-pull” compressional waves
b. S-waves: shake particles at right angles to the direction of travel
3. Mechanical boundaries of the core
a. Inner core
i. 1000 km in radius
ii. Very dense and hot
b. Outer core
i. Liquid
ii. Same composition than inner core
iii. Less dense and cooler
4. Mechanical boundaries within the mantle
a. KNOWN THE DIAGRAM ON THIS SLIDE
b. Lithosphere- includes crust and upper mantle
c. Asthenosphere- weak, easily deformed mantle (100-600 km)
d. Mesosphere- more rigid due to increased pressure
e. Velocity of p-waves slowdown 100 m in (base of lithosphere)
f. S-waves completely slowdown 100 m in
5. Lithosphere defines plate tectonics, not the crust
6. Plate tectonics
a. How these lithospheric plates move and interact with each other
7. History of plate tectonics
a. Fairly recent discovery (1960’s)
b. Before plate tectonics
i. Continental drift theory
1. Edges of continents fit together
2. Alfred Wegner suggested the idea of Pangea
a. Supercontinent of the past that broke apart to form modern
continents
3. Evidence
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