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 sink