News of the WeekGEODYNAMICS

A Lava Lamp Model for the Deep Earth

Science  19 Mar 1999:
Vol. 283, Issue 5409, pp. 1826-1827
DOI: 10.1126/science.283.5409.1826

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For decades researchers have debated whether the mantle, the vast layer of viscous rock between Earth's molten iron core and the outer shell of tectonic plates, is neatly divided at a depth of 660 kilometers into two layers that never mix, or whether it churns from top to bottom over the eons. Now in this issue of Science (beginning on p. 1881), seismologists and modelers offer a new model that incorporates elements of both. In this model Earth's radiogenic heat--abetted by plunging tectonic plates--causes the bottom mantle layer to vary markedly in thickness, bulging upward in some places and squeezing close to the mantle floor in others, but a very deep rock layer, from 1700 kilometers or so down to the base of the mantle at 2900 kilometers, remains intact.