Plate Tectonic: Driving Forces
Transform Fault locking stress
Friction between plates as they grind past each other resists pate motion Causes earthquakes
Slab pull
Gravitational pull on the cold dense slab as it sinks into the mantle at subduction zones ** Drags the plate away from the spreading ridge**
Gravity
If the plates are not passive rafts on the convecting asthenosphere, what makes the tectonic plates move?
Passive model
In test 3, which model shows as a ridge migrates to a trench the hot, ascending and cold descending limbs of deep mantle convection currents converge
Active model
In test 3, which model shows that a plate with a ridge at its trailing simply sinks into the trench
Coupled
One end-member model that shows currents in the mantle raft the overlying plates around Traction stresses at the base of the plates are the drivers
Decoupled
One end-member model that shows plates move due to internal body forces, and influence the shallow convection current pattern in the mantle
concentrated just above the core-mantle boundary
Seismic tomography suggests that subjected lithosphere slabs may end up
Ridge spacing
Test 1
Jumping and propagating Ridges
Test 2
Ridge meets trench
Test 3
Ridge push
the process that helps to move an oceanic plate toward a subduction zone
Basal shear stress Transform fault locking stress
2 Tectonic Resistive forces
Slab Rollback
Downward pull of gravity causes the cold, dense slab to roll back as it sinks into the mantle
Passive model
For test 2, which model requires that each ridge jumps reflects change in pattern of convection.
Active model
For test 2, which model shows that propagating ridges are simply cracks that tap nearby magma sources in the asthenosphere
Trench Suction
Friction between overriding and subjecting plates causes locking at the trench
Basal shear stress
Traction between the plate and the underlying mantle inhibiting plate motion DRAG between the lithospheric plate and underlying mantle in a decoupled convection system
Ridge push Slab pull Trench Suction Slab Rollback
What are the 4 tectonic driving forces?
new lithosphere
What cools and thickens as it moves away from the ridge?
It expands at decreased pressure
What happens as mantle rock rises?
Passive model
What implies that the size and location of ridges and trenches is determined by the position of deep mantle convection cells in test 1?
Active model
What model shows ridge transform offsets explained as cracks that occur when the initial boundary between two diverging plates is not perpendicular to the direction of plate motion in test 1?
upwelling zones
Where does the passive model suggest mid ocean ridges will occur?
downwelling zones
Where does the passive model suggest subduction zones will occur?
A
Which of the following best describes the most well-accepted theory of tectonic plate motions? a. Tectonic plate movement is driven by gravitational forces associated with the more dense lithosphere floating atop the less dense asthenosphere. b. Tectonic plate movement is a result of convection within the mantle, where the plates are passive rafts. c. Tectonic plate motion is a result of density variations within the mantle. d. Tectonic plate motion is driven by convective circulation within the Earth's inner core.
B
Which of the following statements regarding tectonic plate motions is true? a. Slab drag is a tectonic driving force that pulls the plates along atop the convecting mantle. b. Slab pull is a tectonic driving force that causes dense lithospheric plates to sink down into the mantle as a result of gravity. c. Trench rollback is a tectonic driving force that causes lithospheric plates to be subducted. d. Transform fault locking stress causes earthquakes at subduction zones.
Hot buoyant crust
Why are ridges elevated relative to surroundings?