Geophysics

Modeling the Mantle

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Science  03 May 2002:
Vol. 296, Issue 5569, pp. 809
DOI: 10.1126/science.296.5569.809c

Earth's mantle makes up most of the outer half of the planet. Decades of seismic and geochemical studies have revealed a far-from-complete view of the flow and dynamics in the mantle, which affect Earth's heat flow, gross topography, and the composition of many volcanoes. A recent view is that the deep mantle forms a distinct chemical region beneath an irregular boundary that undulates over many millions of years and extends about 1500 km from the base of the mantle. But this region has been difficult to resolve seismically.

Tackley, in a series of numerical models, examines what this deep layer might look like and how various conditions would be expressed in seismic data. Although it is possible to balance a hotter region with a denser chemical composition to reduce the seismic signature, other factors should produce layering that is not observed. Other models can fit some, but not all, of the constraints, so models based on seismic data do not converge with geodynamic models. Stay tuned.—BH

Geochem. Geophys. Geosys.3, 10.1029/2001GC000167 (2002).

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