Question

9. Which is NOT true of the asthenosphere? b. the layer below the lithosphere that allows the overlying lithosphere to move over it c. allows vertical motions to occur in the overlying lithosphere and crust d. probable major source of mafic magmas and igneous rocks in the crust

Answer 1

Answer:

d. probable major source of mafic magmas and igneous rocks in the crust

Explanation:

• The asthenosphere is a layer of Aluminum and silicate and magnesium below the surface of the lithosphere and is made up of oceanic crust that is heavier and denser as compared to the rocks from above.  

• Being a highly vicious and mechanically weaker layer it has an average depth of 200 kilometers below the surface and is divided into three layers of surfaces like the upper, lower and transitional layers.

• The upper and lower are solid and transitional one ios semi is in nature. Its boundary has a surface temperature of 1300 degrees. And in its upper parts, the plates tend to move in and out of the zones.

• Various subduction zones are found in this layer of the asthenosphere. The lower part is thus considered as a major source of id oceanic ridges.