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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A) related to one another, but are not the same thing. B) responsible for all the good in the world. C) responsible for all the bad in the world. D) fundamentally different from each other.
The Ekman spiral is caused by ________
A) density differences in the water column B) the wind and gravity C) the wind and the Coriolis effect D) the pycnocline E) pressure gradients
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A) ground troops B) drone C) nuclear D) cyber E) none of the above
What percentage of its energy needs does the United States import each year?
A) more than 90 percent B) about 70 percent C) about 50 percent D) about 33 percent E) about 20 percent