Plate Tectonics Study Guide

Plate Tectonics

Plate Tectonics theory: plates of rigid, rocky, hard lithosphere "floating" on hot, mushy asthenosphere, ocean lithosphere is thin and heavy, continental lithosphere is thick and light weight; ocean plates are continuously being created and destroyed, continental rocks are neither created nor destroyed,

Plate Boundaries:

divergent - plates move away from each other (usually 2-15 cm/year), new ocean lithosphere created at mid-ocean ridges, relatively gentle, lava flow type of volcanoes, small magnitude, shallow depth (<40 km) earthquakes, mid-ocean ridges begin as continental rifts, Salton Sea for example

convergent - plates move toward each other, subduction zone, ocean crust destroyed at depth, trench, forms volcanic arc or volcanic island arc of explosive, dangerous volcanoes, huge, deep earthquakes (up to 700km and M 9); continental collision, folding and faulting as huge mountains form

transform - lateral motion of plates, lithosphere neither created nor destroyed, earthquakes of variable size and depth, but less than subduction zone, seldom forms volcanoes, no obvious landforms, San Andreas

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Compare and contrast lithosphere and asthenosphere. What are the differences between oceanic and continental plates?

Compare and contrast the three types of plate boundaries in terms of: motion of the plates, landforms, types of volcanoes, size and depth of earthquakes, and location in California (on map).

Why are very old rocks found on continents (up to nearly 4 billion years old) when no rocks older than 200 million years are found on oceanic plates?