plate movement Flashcards
continental drag hypothesis
the hotter and less dense part of the mantle will float upwards towards the crust - lateral movement then occurs which cools the mantle - causing temperature to fall and for the area to fall towards the core creating a convection cell
what is ridge push
where plates move apart, at a mid ocean ridge - molten magma rises - heats the surrounding rock
how are the slopes created
as the asthenosphere and lithosphere at the ridge are heated - they expand and become elevated above the surrounding sea floor - creating a steep slope
because the rock that forms the magma is very hot at first - it is less dense and more buoyant than the rocks farther away from the mid ocean ridge
what happens when the rock ages and cools
as the newly formed rock ages and cools - becomes more dense - gravity the causes this older denser lithosphere to slide away from the ridge - down the sloping asthenosphere
as the older denser lithosphere slides away - new molten magma wells up at the mid ocean ridge - eventually becoming new lithosphere
what is a slab pull
occurs at a subduction plate boundary - one plate is denser and heavier than the other plate - the denser heavier plate begins to subduct under the plate that is less dense
the edge of subjecting plate is colder and heavier than the mantle - continued to sink - pulling rest of the plate with it
ridge push summary
a theory which suggests at the mid ocean ridge there is a pushing on the plate from the elevated newly created crust
slab pull summary
a theory which suggests that at the subduction zone - pull from a colder, older, heavier and subjecting crust
what is positive buoyancy
occurs when an object is lighter than the fluid it displaces - the object will float because the buoyant force is greater than the objects weight
