31 - • SEE DIAGRAM • Plates are not always exclusively...

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GEOL 240 8/31/10 Plate Tectonics: 1. Eq. Belts define edges of about a dozen large, thin, rigid tectonic plates that cover the earth. Plates are made up of lithosphere—100 km thick Move relative to one another by sliding on a weak, softer layer called the aesthenosphere 2. All techtonic activity (mountain building-Greek for “builder”) Eqs, volcanoes, mountains occurs at boundariesof tectonic plates 3. Three types of plate boundaries: (SEE DIAGRAMS) a. Divergent-move away from each other i. Ex: Mid-Atlantic Ridge ii. Iceland is the only place where the mid-atlantic ridge comes to the surface b. Convergent-move towards each other c. Transform-move past each other horizontally Type of Magma Basalt, erupted at mid ocean spreading centers, dark colored, very runny (low viscosity) All abyssal plains are 5 km deep Shield Volcano, Iceland a. Low slopes because of the low viscosity of the magma
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Unformatted text preview: • SEE DIAGRAM • Plates are not always exclusively continental or oceanic, some plates can be both ** • Olduvai Gorge—important because it is where some early discovered were made • Lucy • The Atlantic and Indian Ocean Floor Niger Failed Rift Arm (aulochogene) • Intra-Plate Earthquakes-Rare by sometimes large o New Madrid, MO –three large eqs. (M7-7.5) Winter of 1811-1812 o *1811 and 1812 THREE large earthquakes • Convergent Margins:-Usually one plate slides underneath the other = subduction -Notice Wadati-Benioff Zone SEE DIAGRAM o Deepest Eqs in the world are associated with subduction zones, and they go deep as 670 km deep earthquakes different than surface earthquakes. o Different from San Andreas earthquakes o Earthquakes associated with Convergent plate margins...
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