Publications: 60 | Followers: 0

Tectonics

Publish on Category: Birds 0

Fe/Ni
Fe/Mg
IncreasingFe towardcore
IncreasingSi towardsurface
There are certain trends in Earths chemistry.The crust is relatively depleted in Fe, Mg and enriched in Si, O
Effect ofchemicaldifferentiation
There are certain trends in Earths chemistry.The crust is relatively depleted in Fe, Mg and enriched in Si, O
Earth’s magnetic fieldemanates from thecore complex andsurrounds the planet.Magnetism gainedfrom early nebula ismagnified by turbulentiron, nickel fluid ofouter core.Magnetic fieldenvelopsentireplanet
Polarity+-tends to reverse and fluctuate with time
MANTLE PLUMESwarm rock rises, cool rock descends
How will the lithosphere respond to a plume?
Earth is probably not built ofuniform layers, it is likely mixed somewhat by convection
The continental rifting process

a
q
Kk
Main Types of Plate Motion
ConvergentDivergentTransform
The role ofpartial melting
Granite
Basalt
Partial meltingoccurs when some minerals meltwhile others remain solid because their melting point has not been reached
Subduction
ContinentalCrust
OceanicCrust
AccretionaryPrism
VolcanicArc
Trench
Rifting
SpreadingCenter
Granite
Basalt
PartialMelting
3 Types of PlateBoundaries
CONVERGENTOne plate dives beneath another (subduction) or two plates collide without either subducting.
DIVERGENTNew lithosphere forms as plates pull apart.TRANSFORMPlates grind past each other.No change in Lithosphere
Convergent boundary – 3 types
Ocean-continentconvergent boundary
Plate of oceanic crust collides with plate of continental crust. Oceanic crust issubducted(goes under) continental plate.
Ocean-ocean convergent boundary
Two oceanic crust plates collide. Older, denser plate usually subducts, site ofIsland Arcformation.
MEGATHRUST EARTHQUAKE
OCCURS WHEN “LOCKED” SUBDUCTION ZONE RUPTURES
Strain accumulates.Crust shortens.Uplift occurs.Plates unlock.Crust extends rapidlyculminating in aMegathrust Earthquake
http://www.youtube.com/watch?v=QDqskltCixA
http://www.youtube.com/watch?v=WaUk94AdXPA
Some videos to consider giving in class.
Continent-continent convergent boundaryOROGENESIS



Divergent Boundary
Seafloor spreading leads to the formation of new crust that, compared to continental crust, is relatively enriched in iron and magnesium and depleted in silica (SiO2) (because it reflects thechemistry of the mantle).As two plates continue to move apart, the rock in the seafloor grows older as its distance from the rift zone increases, and as it ages, it cools and becomes denser and is buried under marine sediments that are deposited on the seafloor.
Mid-Ocean RidgeSpreading Center
Transform boundary(side-to-side plate movement)
Fault“a place where the crust is broken and the broken edgesare offset relative to each other(either vertically or horizontally)”
Transform BoundariesConnect Two Spreading Centers
Occur where two plates slide past each other.Motion calledshearing.Connect two spreading centers (less commonly, two subduction zones).Probably the most famous transform boundary in the world is the San Andreas Fault.
oceanic fracture zone
Transform Boundarywithinactive(fracture zone)andactive(transform fault) portions.

Lithospheric Plates Carry Continents and Oceans.
Earthquakes Tend to Occur at Plate Boundaries.
MODERN CONTINENTS EVOLVED FROMPANGAEA
Plate Tectonics explainschains of volcanic islandsHot Spots
Plates have divergent, convergent, and transform boundaries.
the “Ring of Fire” the most seismically and volcanically active zone in the world.
Paleomagnetismconfirms the seafloor spreading hypothesis

Geomagnetic field switches fromreversed polaritytonormal polarityon irregular basisIron crystals in magma incorporate Earth’s new magnetic orientationIron-rich sediment particles align with geomagnetic field like compass needles.
WHEN LITHIFIED, MAGMA AND SEDIMENTS PERMANENTLY RECORD ORIENTATION OF GEOMAGENTIC FIELD AT THAT TIME!
Paleomagnetism at Divergent Plate Boundaries
Two or more plates pull apart.Molten material rises through Rift ZoneNewest magma on either side of rift.Like conveyer belts, the newer crust travels away from the center on each side.Oceanic crust records reversed and normal polarity episodes
.
Magnetic stripingon either side of oceanic ridge.
RIDGE
Rocks can be divided into two groups:normal polarity,magnetic polarity same as today.reversed polarity.
http://www.youtube.com/watch?v=ecGzjo73vUc
http://www.youtube.com/watch?v=GWSivxJ6IqM
Some videos to consider giving in class
Plate Movement Powers theRock Cycle

0

Embed

Share

Upload

Make amazing presentation for free
Tectonics