Tectonics 1 Flashcards
Includes Examples for every structure
What is the plate tectonic theory? What does it explain?
- Earth 3-layered structure
- Earth’s litosphere broken up, huge pieces (tectonic plates)
- plates alwayz moving
- Plate movements -> landforms phenomena
Earth’s structure
Crust, uppermost mantle, mantle, core
What does Litosphere contain?
Litosphere = Tectonic Plate
- Crust, uppermost mantle
Uppermost mantle is Solid.
Tectonic Plates
https://docs.google.com/document/d/12rAwkWXiw5RGFDGpRY3RhY_ab2Cs2ZpI7u36Bog2OvM/edit Page 2
Two categories of crusts and where they are found
- oceanic (seafloor)
- continental (continents)
Oceanic denser
What does the asthenosphere contain?
Semi-solid Upper mantle
What causes the athenosphere to be semi-solid?
Heat from core
causes rocks
Athenosphere melt
Semi-solid Upper mantle, Athenosphere same thing
Core mantle crust temperature thickness
Core: 4400-6000deg, 3300km
Mantle: 1000-3700deg, 2900km
Crust: Lowest, 6-70km
Describe what happens at divergent, convergent and transform boundaries
Divergent -> Plates move away from one another
Convergent -> towards
Transform -> slide past
How does convection currents lead to divergent plate movement?
- Heat from Earth’s core -> mantle material decrease, density
- Mantle material rises surface
- Rising convection currents spreads magma under plates, dragging them apart.
- Mantle loses heat, sinks back towards core
- material gets heated up again
- repeat process
How does slab-pull force contribute to convergent plate movement?
- two plates converge, denser crust pulled down, gravity
- subduct under less dense crust
- sink under it’s own weight, pull down rest plate with it
Subduction
- what is it?
- happens to what crust. why?
Happens to…?
Oceanic crust only.
Continental crust, 2 little density subduct
Descending under another plate
Magma VS Lava
same thing except for location
Magma -> In the volcano
Lava -> Outside of volcano
How is a Fold Mountain formed?
Two plate converges, buckles, folds, forming fold mountains
Evidence of Seafloor Spreading. What does it show?
Rocks age @ seabed pattern
pattern
- Nearest, center mid-oceanic ridge = youngest
- Further away, progressively older
Pattern shows how new oceanic crust is created @ o-o divergence boundary
What is Magnetic Striping?
- Zebra-like pattern strips, normal polarity rocks alternate alongside reversed polarity rocks
- symmetrical both sides
Explain Normal Polarity in Earth
Geographic North, South does not change
Magnetic North, South reversed multiple times
MN points towards GN, MS points towards GS, normal polarity
Why/How does Magnetic Striping occur
- iron-rich lava erupts, cools solidifies
- forms basaltic (rich in iron) rocks, make up seafloor
- Magnetic materials align towards Earth’s local magnetic force at that time, forming (what is magnetic striping)
recording evi of polarity at that time
1 Divergent Boundary example
North American, Eurasian Plate
1 Convergent Boundary Example
Nazca, South American Plate
What forms at o-o divergent plate boundaries?
- Mid oceanic ridges
- Volcanoes
- Rift valley
- Earthquake
How does Mid-Oceanic Ridge + Oceanic Crust form?
- Two oceanic plates move apart
- Decrease in overlying pressure
- Magma rises thru weak areas in crust, fills gaps caused by diverging plates
- Lava cools, solidifies to form basaltic rocks
- Rocks make up new oceanic crust -> mid oceanic ridge
Mid oceanic ridge forms aft new oceanic crust
- Heat from Earth’s core -> mantle material to decrease in density
- Mantle material rises to surface
- Rising convection currents spreads magma (melts due to increase overlying pressure) beneath plates, dragging them apart.
Example of Mid-Oceanic Ridge
Mid-Atlantic Ridge
LINK
Recall the example for o-o divergence
Eurasian and North American Plate diverge
What is formed in divergent c-c plate boundaries?
- Rift valley
- Volcanoes
- Earthquakes
Same As O-O diverge except for no mid-oceanic range
Example of Rift Valley
East African Rift Valley
Example of Volcano
Mount Kenya
Example of Oceanic Trench
Mariana Trench
What forms at convergent oceanic-oceanic boundaries?
- Oceanic trench
- Volcanoes
- Earthquakes
What forms at c-c convergence
- Fold mountains
- Earthquakes
Example of a fold mountain
Himalayas
What forms at oceanic-continental convergent boundaries?
- Oceanic trench
- Volcanoes
- Fold mountains
- Earthquakes
what is a chain of volcanoes called?
island arc
What forms at transform plate boundaries
- faults
- earthquakes
Example of fault
San Andreas Fault, USA
North American Plate slide past Pacific Plate
