Two opposing viewpoints exist concerning the an elasticity of the mantle. One viewpoint (the largest by far) maintains that convection is possible, whereas the other viewpoint maintains that it is not.
After the relevant data were reviewed with the object of reconciliation, it was concluded that plate tectonics and convection may be implausible and that, although the lower mantle is nonconvective, it is overlain by an irregularly convecting region in which the elasticoviscous law may dominate. The lower mantle is inferred to obey a Lomnitz-type law, in which the decreasing rate of creep with time is associated with grain growth in a material already having a large grain size.
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Plate Tectonics—Assessments and Reassessments
The general theme of this publication is the assessment and reassessment of various data, observations, and ideas about the earth as they relate to the concept that has come to be known as plate tectonics. Much widely scattered material was brought together for this publication, and its 24 papers contain an abundance of worldwide references that are important in studying plate tectonics.