Chapter 2-Plate tectonics Flashcards
When did the theory of plate tectonics start and when did it become accepted?
Started in the 1960’s and was accepted my most all geologists by 1968
How many tectonic plates are there?
20
Where do earthquakes occur in relation to tectonic plates?
On the boundaries of the plates
How do divergent plate boundaries interact?
They go away from each other. E.g. a mid ocean ridge
What is the difference between active and passive continental margins?
Passive are far from plate boundaries, active are beat plate boundaries
How do convergent boundaries interact?
Come together e.g. continental shelf or subduction zone.
How do transform boundaries interact?
Slide side by side e.g. a fault
What is a pillow basalt?
Magma that cools under water commonly on the ocean floor
What are dikes?
Preserved magma conduits
What is gabbro?
Below dikes made from magma
What angle does a subducting plate usually dive into the mantle?
45 degrees
What kind of earthquakes occur at subduction zones?
Wadati-Benioff earthquakes
What unique features are associated with subduction zones?
Acretionary prisms
Volcanic arcs
Back arc basins
What is a back arc basin?
A marginal sea behind a volcanic arc
What are 2 indicators of a transform boundary?
Earthquakes and an absence of volcanism
What is a triple junction?
Where three plate boundaries coincide. Eventually they migrate
What is a “hot spot”?
A volcanic plume independent of tectonic plates made of magic magma from the lower mantle
What is continental rifting?
Where the continental lithosphere stretches and thins
Where are some examples of rifting?
East Africa Arabian peninsula is pulling away from Africa
What happens when two continental plates collide?
Oceanic plate subducts and plates collide to form mountains.
What are the driving mechanisms of plate motion?
Elevated mid ocean ridges push lithosphere away, gravity pulls a subducting plate downward, and the convection in the aesthenosphere adds or subtracts
