Describe what a convection current is and how it move materials within the earth

Convection Current: the transfer of heat by the mass movement of heated particles into an area of cooler fluid

Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior of the Earth to the surface ... Secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension and mantle plumes.