The part above the asthenosphere in the upper mantle
According to the research on the propagation of seismic waves in this layer, scientists believe that the chemical composition of this layer is mainly composed of magnesium and iron silicates, and the average chemical composition isPeridotiteIt is similar, so it is named "peridotite".
Compared with the crust above it, its Al and Si contents are significantly reduced, of which the SiO2 content is below 45% (the average of the crust is about 52%);The content of Mg and Fe increased significantly, with MgO accounting for about 40% and FeO accounting for about 10%.So some people call it“Silicon magnesium layer”(But some people also put theBasaltIt is called "silicon magnesium layer").
