Convection Currents and Sea-Floor Spreading
Feb 22, 2016
Convection Currents and Sea-Floor Spreading
Convection Currents• Occur in the asthenosphere• Heat from the core (both inner and
outer) drives the convection currents• Hotter material rises to be just below
the lithosphere because it is less dense
• Then it moves across, moving the lithospheric (tectonic) plate with it
• When it cools it sinks (because it is more dense) and draws the lithosphere down with it
Sea-Floor Spreading• Occurs at a mid-ocean ridge• Magma rises to the surface
becoming lava• Lava spreads the plates apart and
creates new crust• So, younger rock is found at mid-
ocean ridge & older rock is found at farthest point away from ridge