EESA06H3 Study Guide - South American Plate, Nazca Plate, San Andreas Fault
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Can split continents
How do mountain ranges form?
Orogenies and Plate Convergence
Orogeny (Mountain/Formation) – is an episode of mountain building, intense deformation of the
rocks in a region.
o When an island arc collides with a continent it destroys oceans by subduction
o Flipping Subduction Zone - Direction of the new subduction is opposite to the
direction of the original subduction
o Mountain belts form when an ocean basin closes and continents collide
o EX. Appalachian Mountains
o DIAGRAM PAGE 51
o EX. South America plate overriding the Nazca plate
How do plate change over time?
Nothing is fixed in plate tectonics (boundaries, subduction, etc.)
California’s San Andreas Fault
A transform boundary
Trying to jump inland again
Plate’s sizes can change (smaller, larger, etc.)
Nazca Plate = Smaller
North America Plate = Larger
What causes plate motions?
Convection in the mantle
Movement of mantle rock beneath the plate
Why do plates diverge and sink?
1. Ridge push – as plates move away from a divergent boundary it cools and thickens,
plates are pushed apart and slide downhill on the sloping boundary between the
lithosphere and asthenosphere
2. Slab-pull – dense leading edge of a subducting plate sinks down into the asthenosphere
3. Trench-suction – plates fall into the mantle at angles steeper than their dip and then
trenches and overlying plates are pulled horizontally
How are mantle plumes and hot spots related?
Mantle plumes – narrow columns of hot mantle rock that rise through the mantle from thermal
boundary layers at the base of the mantle
Plumes are able to move plates
Continental breakup caused by mantle plume (DIAGRAM PAGE 58)
Plumes may form hot spots