The Solid Earth - Chapter 6: Plate Tectonics Flashcards
What is the theory of plate tectonics?
The outer rigid lithosphere consists of about twenty rigid segments called plates
Where are plates the thinnest?
The ocean
What is the hotter, weaker zone below the lithosphere?
Asthenosphere
True or false: most mountain building occurs along the plate boundaries
True
The type of boundary where plates move apart resulting in upswelling of material from the mantle to create new sea floor
Divergent
The type of boundary where plates move together, causing one of the slabs of lithosphere to be consumed into mantle as it descends beneath an overriding plate
Convergent
The type of boundary where plates slide past each other without creating or destroying lithosphere
transform
Movement along any boundary requires that _____ be made at the others
adjustments
Most divergent boundaries are situated at the ___ of oceanic ridges
crest
As divergent plates move away from the ridge axis, the fractures created are immediately filled with _____ that oozes up from the hot asthenosphere
molten rock
The mechanism that has produced the floor of the Atlantic Ocean during the past 165 million years when material oozing cools slowly to produce new slivers of sea floor
Sea floor spreading
As the plates move away from the area of upwelling, the broken slabs are displaced downward, creating downfaulted valleys called …
rifts or rift valleys
T/f: As the spreading continues, the rift valley will lengthen and deepen, eventually extending out in the ocean.
True
To maintain balance, while lithosphere is created it must also be ____
consumed
The zone of plate convergence is the site where lithosphere is ____ into the ____
reabsorbed
mantle
When two plates collide, which edge is bent downward and placed beneath the other?
The leading edge
True or false: convergence can occur between one ocean and one continent plate, two ocean plates, or two continent plates
True
If the leading edge of a plate capped with continental crust converges with one of oceanic crust, which will appear “floating” and which will sink into the asthenosphere?
The continental (less dense) will appear to remain floating and the denser oceanic slab sinks
The region where an oceanic plate descends into the asthenosphere because of convergence is called a _____
subduction zone
As the oceanic plate slides beneath the overriding plate, the oceanic plate bends and produces a ___________
deep ocean trench
The new magma created by a bending oceanic slab in a subduction zone is (less/more) dense than the surrounding mantle rock?
Less
Mountains associated with the volcanic activity associated with subduction of oceanic lithosphere
volcanic arcs
True or false: convergence can cause volcanic activity when some of the magma rises
True
When two oceanic slabs converge, one descends beneath the other initiating _____
volcanic activity
What is formed when volcanic activity is sustained and dry land eventually emerges from ocean depths?
Island arcs
Collision between two continental blocks can be orogenous, and the ____ mountains were thought to have formed in this mmanner
Appalachian
As the continental blocks converge, the intervening sea floor is…
subducted beneath one of the plates
the ____ boundary connects an active spreading center to a subduction zone so facilitates the movement of the crustal matter created at the ridge crest to its destination
Transform
