Plate Tectonics

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Plate boundaries:

Destructive plate boundary - where crust is destroyed as one plate moves under another.

(http://upload.wikimedia.org/wikipedia/commons/2/29/Active_Margin.svg)

Continental - Oceanic: Denser oceanic plate gets forced under lighter continental = subduction. Friction causes major earthquakes. Forms trenches; E.g. Peru-Chile trench and fold mountains; E.g. Andes.

(http://upload.wikimedia.org/wikipedia/commons/8/83/Continental-continental_convergence_Fig21contcont.gif)

Continental - Continental: continents collide, no subduction. Create fold mountains; E.g Himalayas

(http://upload.wikimedia.org/wikipedia/commons/0/0c/Oceanic-oceanic_convergence_Fig21oceanocean.gif)

Oceanic - Oceanic: Occurs offshore. Crust subducted may be denser or moving faster. Forms island arc - line of volcanic islands which can become land masses; E.g. Japan (Pacific under Eurasian). Also forms ocean trench; E.g. Marianas trench.

Constructive plate boundary: where plates move apart in oceanic areas, the space is then filled with basaltic lava. Forms mid-ocean ridges in oceanic areas, If occur on continental crust a rift valley will be…

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