How is the mantle divided?

The mantle is divided into the upper and lower mantle based on variations in temperature, composition, and physical state. The upper mantle, which extends from the crust down to about 410 kilometers, is partly molten and contains the asthenosphere, which is less rigid and behaves more like a viscous fluid. This allows for the movement of tectonic plates at the Earth's surface.

The lower mantle, stretching from about 410 kilometers to the outer core, is composed of solid rock but is under immense pressure and heat, causing it to behave differently than the upper mantle. The transition between these two layers is marked by changes in mineral composition and pressure conditions, leading to distinct physical properties in each layer. Thus, the division into upper and lower mantle reflects a key aspect of Earth's internal structure and behavior.