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Convection in the Asthenosphere Convection is the motion of a fluid which is heated unevenly. This is a means of energy (heat) transfer in a fluid. The fluid "carries heat with it" due to circulation. Conduction: energy transfer through a solid. Radiation: energy transfer trough space (no medium), medium = material Heated Fluids will rise due to lower density. Cool Fluids will sink due to higher density. The plastic layer of the earth is called the asthenosphere. It has some properties of a solid, yet flows over geologic time. The interior of the earth continues to be heated due to radioactive decay. This heat is conducted through the earth, heating the asthenosphere. Heated material rises until it bumps into the bottom of the lithosphere; then it flows across, carrying lithospheric plates. Contact with the frozen plate cools the upper mantle; this material then sinks.
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