Scientists have subdivided the upper mantle into three sections based on environmental and compositional differences. What are these three subdivisions and how do they compare to each other?
What will be an ideal response?
Answer: The uppermost mantle is the lithospheric mantle, which is slightly lower in density and solid. Next down is the asthenosphere, which is similar in peridotite composition to the lithospheric mantle, but is hotter and less rigid, thus allowing lithospheric plates to move over it. The lowest subdivision is the transition zone. This is also where mineral phase changes occur to transform olivine to spinel.
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