geography Flashcards
b3 minimum please
rift valleys [continental - continental ]
when continental- continental plates move apart the rocks fracture and form parallel faults the rocks between the parallel faults collapse to form a deep rift valley with steep sides for example the Nubian plate moves away from the Somalian plate to form the great riff valley
rift valley [ oceanic - oceanic ]
when 2 oceanic - oceanic plates move apart at the divergent plate boundaries magma rises through the weak crust of the earth surface to fill up the gaps the lava cools and solidify into basaltic rocks forming new oceanic crust and at the center of the ridge is a deep rift valley with steep sides
oceanic trenches
when the oceanic- oceanic plates collide or when the oceanic- continental plate collide both at the convergent plate boundary this would cause the denser oceanic plate to subduct and form a large depression known as an oceanic trench for example the Nazca oceanic plate collide with the continental south American plate to form the peru- chile trench
or the oceanic pacific plate subduct beneath the Philippine oceanic plate
fold mountains [oceanic continental ]
fold mountains happen when the oceanic plate boundary and the continental plate boundary collide at the convergent plate boundary due to the enormous pressure this causes the rocks of the continental plate to buckle and form a fold mountain for example the denser nazca plate subducts beneath the continental southern amercia plate to form andes fold mountains
mid oceanic ridge
the mid oceanic ridge form when 2 oceanic oceanic plates move away in the divergent plate boundary the decrease in overlying pressure causing mantle to melt forming magma and rise through the weak areas of the surface of the earth and fill up the gaps and which the lava cools and solidifies into basaltic rock which forms new oceanic crust which this forms an extensive underwater volcano on the ocean floor known as the mid ocean ridge and some examples of such is the oceanic north American plate moves apart from the Eurasian oceanic plate to form the mid atlantic ridge
fold mountains [ continental - continental ]
fold mountains happen when 2 continental pates collide at the convergent plate boundary however the continental plate do not subduct as they are too bouyant so the enormous pressure causing the rock of the continental plates to be uplifted and buckled forming a folded mountain for example the Indo Australian continental plate collides with the continental Eurasian plate to form the Himalayan mountain range
volcanos divergent plate boundary
when 2 continental plate move apart at the divergent plate boundary the decreasing the overlying pressure causes part of the mantle to melt forming magma and which the magma seeps through the weak area of the earth surface forming a volcano for example mount kenya and mount kilimanja
when 2 oceanic oceanic plate move apart at the divergent plate and magma rises through the weak areas forming submarine volcanos and after many eruption the surface of the ocean may break from the ocean up the surface forming volcanic islands
volcanos at the convergent plate boundary
when continental plate collide with a oceanic plates at the convergent plate boundary and when the denser plate boundary subducts into the mantle the high pressure forces the water out of the oceanic plate and the water decreases the melting point of the overlying mantle and melt the mantle material and form magma and rises through the weak area of the earth surface and form volcanos at the continental plates for example the nazca oceanic plate subducting into the south american oceanic plate and form nevado del ruiz volcano
when 2 oceanic plates collide at the convergent plate boundary and this causes the denser plate to subduct and the large pressure forces water out the oceanic plate and it decrease the melting point of the mantle and the overlying mantle causing the mantle material to melt forming magma that rises through the weak areas of the earth surface and form chains of volcano known as volcanic islands
for example oceanic pacific plate subducts into the oceanic phillipine plate to form mariana islands
