The Mantle

• The mantle is a mostly rigid layer lying beneath Earth’s crust.

• It is the largest of Earth’s four main layers, accounting for about 85% of Earth’s volume and about two-thirds of Earth’s mass.

• The mantle is composed of silicates that are higher in iron and magnesium than rocks in the crust.

• The mantle consists of three distinct zones – the upper mantle, the asthenosphere and the mesosphere.

• The upper mantle (lithospheric mantle) is a region of rigid rock, similar to the crust.

• The upper mantle and crust are collectively referred to as the lithosphere.

• Hence, the upper mantle is also known as lithospheric mantle.

• The asthenosphere (transition zone) is a region of ‘plastic’ rock, which can flow slowly over long periods of time.

• The mesosphere (lower mantle) is a region of rigid rock.

• The mesosphere is more solid than the asthenosphere, even though it is much hotter, because it is under higher pressure.

The mantle consists of the upper mantle, the asthenosphere and the mesosphere.

(Image: elina33, Adobe Stock)