 Advection, referring to the transfer of mass and heat, occurs when a moving fluid carries substances or heat to or away from a source and through a surrounding solid along channels.Melts are produced when mantle rocks bear temperatures between 1100 and 2400 °C at corresponding depths (pressure varies the melting temperature) with the presence of water.When melts reach surface via vertical vents, they cool down and solidify forming mafic or ultramafic rocks which are rich in iron and magnesium.