Plate Tectonics Test Flashcards
(26 cards)
Continental Drift Theory
the continents used to be joined, forming a supercontinent
Continental Drift Evidence
continental puzzle, matching fossils, rock types and ancient climates
Why evidence might not be supported
Matching fossils: most people believed in land bridges more than moving continents
Why was Wegener’s hypothesis wasn’t liked?
he was the first to suggest such a thing
Pangaea
our last supercontinent; it means “all land”
mid ocean ridges
long chain of mountains as long as the ocean
deep ocean trenches
curved valleys on the edge of ocean basins
Harry Hess
published a theory of sea floor spreading
sea floor spreading
when new ocean floor opens on mid ocean ridges and slowly moves outward then sinks again
Evidence for sea floor spreading
magnetic strips, earthquake patterns, and ocean floor age
ocean floor is less than 200 million year old because. . .
anything older would have entered the mantle and melted
Earthquakes at depth of 700 km. . .
don’t happen because at that point, they enter the mantle and melt
theory of plate tectonics
Earth’s lithosphere plates move slowly, driven by currents in the mantle
3 plate boundries
Divergent
Convergent
Transform
Divergent
the plates move away from each other
Convergent
the plates collide with each other
Transform
the plates slide sideways past each other
divergent is a constructive plate margin because. . .
its where new oceanic lithosphere is produced
oceanic lithosphere collides with oceanic lithosphere
volcanic island arc because under water volcanos form more volcanos and eventually they become islands
oceanic lithosphere collides with continental lithosphere
continental volcanic arc made by the subduction of oceanic lithosphere
continental lithosphere collides with other continental lithosphere
complex mountains because the land crashes and pushes against each other
Cause of plate motions in the lithosphere
the weakness of the asthenosphere allows the stiff lithosphere to shift across it
slab pull
gravity pulls COOL, dense OCEANIC lithosphere down into the mantle
ridge push
gravity causes stiff, OCEANIC lithosphere to slide down the ASTHENOSPHERE which is elevated near mid ocean ridges