VUME Upper Mantle of the Earth

Heat Transfer. Thermo-Chemical Mantle Convection.

Heat transfer There are three modes of heat transfer:
- Conduction.
- Convection.
- Radiation.
Conduction is process by which heat is transferred by direct contact between an object at a higher temperature to one at a lower temperature. Conduction is the transfer of energy through the collisions and vibrations of molecules and atoms. The temperature of molecules is related to their velocity.
The term convection is often used to describe heat transfer that occurs between an object and a fluid flowing across it. Convection is, in essence, a type of conduction. In convection heat is transported mostly by the movement of material, rather than by conduction. Convection in the Earth's mantle is the transport of heat by motion of the mantle. In turn, the distribution of temperature leads to density instabilities (via the coefficient of thermal expansion), which drive the mantle flow.

The simpler process of advection is heat transport by the movement of material without considering the feedback process of the redistribution of temperature affecting the velocity of the material. “Wind chill” is a good example of the advection process. In the Earth's mantle, the advective transport of heat (due to the velocity term) is the dominant way that heat is transported.
The third way an object’s internal kinetic energy and temperature are increased is by exposure to radiant energy, such as the energy coming from the sun. The radiant energy is converted to kinetic energy of the particles in the object. This is why we get hot in the sun.

Mantle Plumes and Heat Flow.

Lower Mantle Superplume A mantle plume is a thermal diapir of hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some of these volcanoes lie far from tectonic plate boundaries, e.g., Hawaii. Others represent unusually large-volume volcanism on plate boundaries, e.g., Iceland. The currently active volcanic centers are known as "hot spots". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some "hot spots".