Plate margins Flashcards
what are destructive plate margins also referred to as?
subduction zones
when does subduction occur? (destructive)
occurs when 2 tectonic plates converge - the older denser plate is subducted
when 2 oceanic plates converge what does subduction form?
an island arc
where an oceanic and a continental plate converge what happens?
FOLD MOUNTAINS FORM
what are fold mountains and how do they form?
due to low density there is not much subduction when 2 plates of continental crust meet instead their edges are forced upwards into fold mountains
how are ocean trenches formed?
form at destructive plate margins between oceanic plates or between oceanic and continental plates
one plate subducts beneath the other
how are island arcs formed?
form during subduction when descending plate encounters hotter surroundings which together with the frictional heat cause the plate to melt
as this material is less dense than surrounding magma. it rises to the surface as magma plumes
how are ocean ridges formed?
formed when plates move apart in oceanic areas
the space between the plates is filled with balsatic lava to form a ridge
how are rift valleys formed?
formed when plates move apart in continental areas the brittle crust fractures and as sections of it move and areas of crust drop down between paralell faults
what happens as a conservatice plate margin?
two plates slide past eachother the movement can be violent and an additonal build up of pressure which eventually gives way which results in earthquakes. no volcanic activity
what are magma plumes?
columns of magma rising through the mantle
what happens at destructive plate boundary?
subduction occurs when 2 tectonic plates converge, the older denser plate is subducted
what happens at constructive plate boundaries?
new crust forms at constructive plate margins where rising plumes of magma from the upper mantle stretch the crust and the lithosphere
what happens at conservative plate margins?
two plates slide past each other
an additional build up of pressure can result in an earthquake
