| Popis: |
Mapping Mantle Mixing Mantle convection is the primary driving force for plate tectonics, but mantle convection also mixes material in the interior of Earth and controls heat flow from the core. The patterns of convection are often difficult to image directly with seismic waves—particularly on a global scale. French et al. (p. 227 , published online 5 September) constructed a global tomographic model of the upper mantle and transition zone that is sensitive to changes in seismic velocity and anisotropy. The approach identifies elongated, horizontal structures in the upper mantle that are parallel to overlying plate motions. At greater depths, however, vertical plume-like structures extend from the lower mantle and disappear near the base of low velocity zones like those observed beneath Hawaii. |
