Dynamical Transport Processes in the Earth's Mantle

Over the last two decades it has become widely accepted that convective flows within the Earth's mantle form the mechanism which turns heat from the Earth interior into mechanical work, thus providing ultimately the mechanism behind all tectonic activities on Earth. Mantle material, while reacting elastically upon short term loads and forces like earthquakes, acts like a viscous fluid in response to forces which are applied over geological time scales. Having recognized the 'fluid' nature of the Earth's mantle, a new dynamic picture of the mantle emerged from the application of concepts from fluid mechanics to the Earth's Interior. Computer models have been designed which allow to study the dynamic transport processes in the Mantle and from which possible evolutionary models of the Mantle can be inferred. From those studies it appears that the flow in the Mantle does not take place in the form of regular convection cells. Complex flow patterns ,fluctuating in time and space seem to be the characteristic style of convection within the Earth's mantle. Slow gradual changes in the flow pattern coexist with spontaneous changes on shorter time scales. The thermal structure of the Earth's interior and also its chemical composition will be widely determined by these dynamical phenomena. An understanding of mixing properties of mantle convection is of key importance in order to be able to interpret results as obtained from geochemical investigations in terms of their geodynamical implications. Recent seismological investigations