Plate Tectonics Flashcards
(30 cards)
Developed the theory of Continental Drift
Alfred Wegener
Created the theory of Sea Floor Spreading
Harry Hess
The two theories of continental drift and seafloor spreading lead to the current theory that Earth’s outer crust (lithosphere) is divided into several plates that glide over the plastic like asthenosphere (upper mantle)
Theory of Plate Tectonics
What is the engine that moves the plates? It is caused by hotter magma rising and cooler magma sinking
convection currents
Layer of rock which forms the continents and the shallow sea beds close to the shore. It is older, thicker and less dense
Continental Crust
A thin layer of crust that underlies the ocean basins, consists mainly of basalt younger and more dense
Oceanic crust
plates that are dividing or moving apart
Divergent boundaries
Plates that slip sideways past one another.
Transform Boundaries
Plates that are colliding
Convergent boundaries
When two oceanic crusts diverge they create this type of feature
Mid-ocean ridge and sea floor spreading
New crust is created at this type of boundary
divergent
What is an example of a divergent boundary when two oceanic plates are moving apart
Mid Atlantic Ridge which comes above the ocean in Iceland
When two CONTINENTAL crusts diverge what type of crustal feature do they form?
rift valley
What is an example of a rift valley?
The Great Rift Valley in Africa
Crust is neither created or destroyed at this type of boundary
transform
Earthquakes are created at this type of boundary
transform
What is the most famous transform boundary found in the US?
San Andreas Fault in California
When two continental plates converge what type of feature is formed?
folded mountains
When a continental plate and an oceanic plate converge what type of feature is formed?
volcanoes
When an oceanic plate and an oceanic plate converge what type of feature is formed
volcanic arc islands
What is an example of folded mountains?
Himalayas
What is an example of volcanoes formed due to continental/oceanic crust colliding?
Cascade Mountains in Oregon and Washington which includes Mt. St. Helen’s
What is an example of a volcanic arc island?
The Aleutian Islands in Alaska
When a continental/oceanic crust converges, which one will subduct?
The continental crust because it is more dense
