4.4: The Mantle

The Mantle

The mantle Links to an external site. is made of hot, solid rock, much of which is composed of silicate minerals Links to an external site. such as olivine Links to an external site.. The asthenosphere Links to an external site., a region of the mantle that is plastic and capable of flow, is likely composed mainly of the ultramafic rock peridotite Links to an external site.. The lower mantle Links to an external site. (mesosphere) is more rigid and rocky and is composed of different silicate minerals, such as bridgmanite Links to an external site..

A cross-section of Earth, illustrating the different layers, including the location of convection cells in the mantle.

Figure 4.3: The convection cells of the mantle (CC-BY 4.0; Chloe Branciforte, own work).

Convection currents Links to an external site., important to the mechanics of plate tectonics, develop as lower mantle materials near the core heat up. These mantle convection cells occur as particles in the rock begin to move more rapidly, decrease in density, rise toward the surface of the Earth. When the warm material reaches the surface, it spreads horizontally and begins to cool. Eventually the material becomes cool and dense enough to sink back down into the mantle toward the core. As the material sinks back to the bottom of the mantle, the material travels horizontally and the process begins again (Figure 4.3).