Mantle convectionMantle convection is the very slow creeping motion of Earth's solid silicate mantle as convection currents carry heat from the interior to the planet's surface. The Earth's surface lithosphere rides atop the asthenosphere and the two form the components of the upper mantle. The lithosphere is divided into a number of tectonic plates that are continuously being created or consumed at plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading.
Core–mantle boundaryThe core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron–nickel outer core, at a depth of below Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the differences between the acoustic impedances of the solid mantle and the molten outer core. P-wave velocities are much slower in the outer core than in the deep mantle while S-waves do not exist at all in the liquid portion of the core.
Mantle plumeA mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries. Mantle plumes were first proposed by J.
