Divergent Boundaries

-tensional forces

-boundaries occur when plates rift, and move apart

-creating large expanses oceanic crust

(characterized)

-volcanism

-normal faulting & graben formation

-sedimentary deposits

-crust (basalt) created in this type of boundary

-new crust added to trailing edge of each seperating plate

-spherical earth requires adjustment of rigid crust

-offsets in the crust exist

-compressional forces

-leading edges of two plates come in contact w/eachother

(CHARACTERIZED)

-metamorphism

-volcansim

-reverse faulted/folded mountains

-sedimentary wedges

-resulting in a deep ocean trench

(rate of plate movements affects the features)

-resulting in devleopment of a deep sea trench

-assoicated w/ volcanic terrains

(METAMORPHISM)

-mixture of broken, jumbled, and thrust-faulted rock

-subduction zone

(mixed up minerals)

-fragments of oceanic crust found on continents

-washed up on contintents

(peridotite>Gabbro>Sheeted Dikes>Pillow Basalts)

buttom to top

-subduction zone

(metamorphism->subduction zone)

-high P, low T

-blue amphiiboles

-basaltic magma rise at newly formed spreading center 

-new oceanic crust forms

-behind & parallel to subduction zone

-sinking subducting plate faster than forward motion of overriding plate which is slower

(tensional stress=pulling)

Transform Plate Boundaries

(shear,strike-slip)

-shear forces

-boundaries occur where one plate moves laterally past another

-crust neither created or lost

(CHARACTERIZED)

-localized metamorphism

-strike-slip faulting

-minor igneous intrustions

Back-arc basins

(cont)

oceanic or extension of contintenal margin progressed to extreme slate it forms by

-behind and parallel to magmatic arc of subduction zone

-resulting by folded

-reverse and thrust faulted mountains

(some igneous cores, others metamorphosed)

-rocks are sutured together

(metamamorphism)

Transform Plate boundaries

(shear, strike-slip)

-shear forces

-boundaries=one plate moves laterally past another

-localized metamorphism, strike-slip faulting, minor igneous intrusions

(crust neither created or lost)

-ancient rock makes up core of continent

-applied to crust that has attained tectonic & isostatic stability

(north america)

-elongate regions of crust that have been intensely folded & faulted during continental collision

-thicker crust then cratons

-eroded roots of ancient mountain ranges formed by collision b/w cratons

-differ by history,age,size

Shield

(continental shield)

-assemblage of cratons & ancient oregens that has reached isostatic equilbrium

(largest)

-thin layer of little-deformed sediments

(canada)

-accumulation of sediment

-stable interior plate

-places where great thickness of sediment accumulates

-meeting point formed by three spreading edges

-angle b/w any two edges is 120°

-spreading continues along two edges

-third edge is failed rift

-former convergent or transform fault margins modified by addition of crust such as (rafted-in, exotic fragments of crust)

(ex.island arc)

-those pieces crust not subducted are accreted

(san andrea fault)

-wet particle melting in mantle activated by water

-released by subducted Nazca Plate produced the andesitic magma 

-margin of continent coincides w/ a transform fault boundary of a plate 

(san andrea fault)