The lithosphere and aesthenosphere are defined on the basis of?

Question

a.differences in composition.

b.differences in the mechanical properties.

Answer 1

The lithosphere is distinguished from the asthenosphere by the fact that it is cooler and therfore, more rigid.The top layer of the lithosphere virtually floats on the  asthenosphere.

So,the crust and the top layer of the mantle form  a cool,rigid layer called the lithosphere. The upper mantle forms a heat-softened layer called asthenosphere.

Answer 2

Because of its density.

Answer 3

The confusion arises because there are Seismologists and Geochemists. Lithosphere and Asthenosphere refer to changes in the mechanical properties of the Earth (seismology - tectonic plates & earthquakes). Whereas, Crust and Mantle refer to the chemical changes within the Earth (geochemistry - types of rocks).

Mechanically speaking, Seismologists define the Lithosphere as the hard & ridged outer ~100 km of the Earth. The Lithosphere includes the Crust and the uppermost (<1300 Celsius) brittle Mantle. Below the brittle Lithosphere (Crust+upper brittle Mantle) is the Astenosphere, a weak plastic layer within the upper Mantle, the Astenosphere is defined as having a temperature >1300 Celsius. Because the Astenosphere is so hot, it is plastic and it permits plate tectonics; the brittle Lithosphere (Crust+upper brittle Mantle) slides over the weak Astenosphere.

Answer 4

Did you actually do ANY of this homework assignment on your own?