Complete option to the question:
A. The asthenosphere is broken up into large continental- and ocean-sized plates.
B. Convection currents within the asthenosphere push magma upward to create new crust.
C. Heat from deep within Earth is thought to keep the asthenosphere malleable.
D. The asthenosphere is the repository for parts of the lithosphere that are dragged downward in subduction zones.
Answer: The correct option is A (The asthenosphere is broken up into large continental- and ocean-sized plates.)
Explanation:
Among the components that makes up the earth crust are the lithosphere and the asthenosphere.
The LITHOSPHERE is the outer layer of the earth structure which consists of the upper part of the mantle and the crust.
The ASTHENOSPHERE is a part of the upper mantle just below the lithosphere that is involved in plate tectonic movement and isostatic adjustments. It is denser and weaker layer of the upper mantle which permits the movement of tectonic plates in the lithosphere.
The asthenosphere is the repository for parts of the lithosphere that are dragged downward in subduction zones.Heat from deep within Earth is thought to keep the asthenosphere malleable. And the convection currents within the asthenosphere push magma upward to create new crust. But it is not broken up into large continental- and ocean-sized plates.
