Chapter 4 - The earth's mantle and core

Abstract

The Earth's core and mantle play important roles in the evolution of the crust and provide the thermal and mechanical driving forces for plate tectonics. Heat liberated by the core is transferred into the mantle where most of it (> 90 per cent) is convected through the mantle to the base of the lithosphere. The remaining heat is transferred upwards by mantle plumes generated in the core-mantle boundary layer. The mantle is also the graveyard for descending lithospheric slabs, and the fate of these slabs in the mantle is the subject of ongoing discussion and controversy. Another exciting mantle topic is that of the origin and growth of the lithosphere, and whether its role in plate tectonics has changed with time. The Archean lithosphere, for instance, is considerably thicker than post-Archean lithosphere, and geochemical data from xenoliths indicates its different origin. Another topic discussed in the chapter is the origin of isotopic differences in basalts that reflect different compositions and ages of mantle sources. It explores the questions as to how the core was formed and whether the core processes affect the mantle processes.