Plate Tectonics

Divergent Boundaries - plates move away from each other,

oceanic spreading centers, create new oceanic crust, surface expression - mid-ocean ridges, volcanism: basalt volcanoes, lava flows, mafic dikes, earthquakes: shallow to intermediate earthquakes; small to medium magnitude, modern example: mid-Atlantic ridge, Iceland

continental rifts; break-up continent, earliest stages of ocean formation, surface expression: rift valley and volcanoes, volcanoes: basalt volcanoes, lava flows, earthquakes: shallow to intermediate earthquakes; small to medium magnitude, modern example: Rio Grande Rift, East African Rift

Convergent Boundaries - plates move toward each other;

subduction zones - requires involvement of at least one ocean plate, destroy ocean crust, surface expression: trench, island arc or volcanic arc, volcanoes: explosive composite volcanoes, earthquakes: Benioff zone; small to huge earthquakes, shallow to very deep (700 km), modern examples: Japan, Philippines, Aleutians, Andes, S. Mexico, Mt. St. Helens

continental collisions: suture continents together, surface expression: forms huge mountains, volcanoes: none, earthquakes: variable in depth and size, modern example: Himalayas

Transform - plates slide side-by-side; neither create nor destroy crust, surface expression: fault which is often hard to identify, subtle landscape variations, volcanoes: none, earthquakes: variable in depth and magnitude, modern example: San Andreas Fault

Driving Mechanisms: convection, slab-pull, ridge-push

Describe the driving mechanisms for plate tectonics.

Be prepared to compare and contrast any types of plate boundaries in terms of plate motions, types of plates involved, surface expression, volcanoes, earthquakes, and modern examples. ( I recommend making a chart with all this information)

Determine the angle of subduction from the arc-trench gap or the distribution of earthquakes.

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