PLATE TECTONICS

Evidence

• Geographic matching continental outlines
• Geologic
• same geol. units across continents
• similar mountain chains across continents

• Climatologic
•  glacial striations in equatorial/tropical positions
• coal beds and evaporites

 
• Paleontologic: same land and fresh water fossils in different continents

THE NEW FINDINGS

• The internal structure of the Earth according to physical properties of the materials;
• Seismic studies:
• Core solid inner core
• liquid outer core

The lithosphere: a rigid layer on top of the asthenosphere. Rigid. (Crust and uppermost mantle).
Oceanic crust: basaltic.
Continental crust: Granitic
Continental lithosphere thicker than oceanic lithosphere.
The asthenosphere:  partially molten
        plastic
        Fully contained in the upper mantle

• Topography of the ocean floor
Mid-oceanic ridge (MOR)
guyots
Sea floor spreading proposed

• Paleomagnetism
magnetic stripes symmetric to the MOR

 
• Ages of the ocean floor stripes
symmetric to the MOR
Older away to the MOR
Sea floor spreading confirmed

ROCK BEHAVIOR
Influenced by stress

Types of stress

• compression
• extension
• shear

Behavior

• brittle at the surface =  Faults
• plastic with depth (at higher P and T) =  Folds

• anticline Symmetric or asymmetric (more common)
• syncline
• dome

• overturned fold

Types of faults
 

• direct or normal (tension) Grabens
• reverse or thrust (compression)
• strike-slip (shear)

PLATE BOUNDARIES
 

Divergent Boundaries (know examples)

East Africa                                                             The Atlantic Basin

The Red Sea                                                         The Pacific Basin

___________________ stress, ___________________ faults, _______________ magmatism
 

Convergent Boundaries (know examples)

_______________________ stress, __________________ faults.

Ocean. lithosphere - ocean. lithosphere:______________________magmatism

Ocean. lithosphere - cont. lithosphere:_______________________ magmatism

Cont. lithosphere - cont. lithosphere: ________________________magmatism
 

Transform Boundaries (know examples)

San Andreas Fault, Faults across MOR.

_____________________ stress, ____________________ faults, ________________ magmatism

• Only denser material is subducted, continental lithosphere is lighter and remains "afloat". No rocks older than Jurassic (200 m. y.) form the ocean floor.

 

Intense volcanism, anchored deeply in the mantle.

Not related to plate boundaries.

Hawaii's case.

Iceland's case.

Yellowstone's case.

• Convection
• Trench pull
• Ridge push

About 2.5 cm ( 1 inch) a a year on average for the world.

THE TECTONIC ROCK CYCLE

• Given that Plate Tectonics continuously reworks rocks between the stages of creation, shifting and destruction of lithospheric plates, the rock cycle can be explained as a consequence of Plate Tectonics

MOUNTAIN BUILDING (OROGENESIS)

 
The break-up of a continent

Hot spot under a continent

upwarp

triple junction

rifting (three armed rifts = two oceans, one failed rift)

coarse clastic continental sequences

basaltic dikes and sills

evaporites

passive continental margins with continental shelf deposits

 

Orogenesis as a result of continental collision

subduction reversal

closure of an ocean => collision => suture zone

uplift of ophiolites

 

 
 

Orogenesis without continental collision

oceanic / continental convergence

magmatic arc ( volcanoes & plutons) = mountain core

regional metamorphism

fold and thrust belt (thrust sheets)

accretionary wedge

foreland basin with flysch deposition

molasse deposition (clastic wedge)

 

Tectonics of continental interiors

As a result of transmitted stresses from mountain building at continental edges

• structural domes or structural basins
concentric pattern of outcrops