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08-28 08_28.jpg |
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| Title: | Proposed models for mantle convection. |
| Caption: | A. The model shown in this illustration consists of two convection layers—a thin, convective layer above 660 kilometers and a thick one below. B. In this whole-mantle convection model, cold oceanic lithosphere descends into the lowermost mantle, while hot mantle plumes transport heat toward the surface. C. This deep-layer model suggests that the mantle operates similar to a lava lamp on a low setting. Earth's heat causes these layers of convection to slowly swell and shrink in complex patterns without substantial mixing. Some material from the lower layer flows upward as mantle plumes. |
| Keywords: | plate tectonics, tectonic plates, sea-floor spreading, divergent boundaries, boundary, mid-ocean ridges, convergent, mantle, subduction, trenches, core |