3 plate tectonics part two Flashcards
Lithosphere and athenosphere
Lithosphere
Rigid (but can bend if there’s a heavy load)
Made up of crust and upper mantle
Asthenosphere
Partly molten
Soft
Able to flow
basic temp and density physics
Heat rises
Density decreases
Cold sinks
Density increases
What provides the motion of liquidish in the asthenosphere
probably not just convection: more complicated see screenshot of warm and cool zones
which came first ridge push or slab pull
The chicken (ridge push)
The spreading at the ridges
The egg (slab pull)
The sinking at the subduction zones
Current thinking
Probably slab pull started the cycle of plate tectonics, but… we don’t know
Earth’s plates
7 main plates: Pacific, Eurasian, African, Antarctic, Indian-Australian, North American, South American
Plate boundaries divergent
divergent
Plates moving apart
Types:
Oceanic
Continental
plate boundaries convergent
Convergent
Plates moving together
Types:
Continental – Oceanic
Oceanic – Oceanic
Continental - Continental
plate boundaries transform
Transform
Plates sliding past each other
Types:
Continental
Oceanic
crust is created and destroyed where?
Crust is created at divergent plate boundaries
Crust is destroyed at convergent plate boundaries
divergent mid ocean ridge
Plates moving apart
Major features:
Volcanic rise
Central rift valley (“rift axis”)
Faults
Examples:
East Pacific Rise
Mid-Atlantic Ridge
divergent continental rifts
Parts of a continent moving apart
Major features:
Volcanism
Faulting
Eventually seafloor creation
Examples:
East African Rift-Red Sea
Our backyard
basin and range(our backyard)
Narrow north-south-trending mountains separated by basins
Horst = Mountain range
Graben = Valley See screenshots to describe these boundaries
convergence key principle oceanic vs continental
Oceanic crust
Younger
Denser
Sinks into the asthenosphere
Continental
Older
Less dense
Will NOT sink into the asthenosphere
convergent: continental-oceanic and earthquake evidence
Plates moving together
Light vs Dense
Major features:
Continental volcanic arc
Trench
Accretionary prism
Examples:
Andes
Cascadia
Aleutian Islands
earthquake evidence : Earthquake depths
Increasing depth of earthquake away from trench
Wadati-Benioff Zone
convergent: oceanic-oceanic
Plates moving together
Dense vs denser
Major features:
Island volcanic arc
Trench
Small accretionary prism
Example:
IBM Arc (Izu-Bonin-Mariana)
convergent continental-continental
Plates moving together
Light vs light
Major features
Folded mountain belts
Examples
Himalayas
Ancient Appalachians
Transform plate boundaries
Sideways motion
Link between other types of boundaries
Major features:
Crust deformed
Not created, not destroyed
Fracture zones
Example:
San Andreas Fault
Between ocean ridge segments
Dead Sea
convergent boundaries can turn from continental-oceanic to continental continental if all fo the ocean is moved beneath and continental plates connect
true blue write it out
mantle plumes
Mantle plumes and hotspot volcanoes
Mantle plume
Rising column of molten rock through the mantle and lithosphere
**Does NOT move relative to the plates’ motions
whys
Why does new oceanic floor get generated at the ocean ridges?
Why does old oceanic floor get pushed and destroyed at the ocean trenches?
Why do the plates move?
When did it all start?
