1. Upper Mantle:

* Lithosphere: This is the rigid outermost layer of the Earth, composed of the crust and the uppermost part of the mantle. It's about 100 km (62 miles) thick and is broken into tectonic plates.

* Asthenosphere: This is a partially molten layer beneath the lithosphere, extending to a depth of about 660 km (410 miles). It's characterized by its plasticity and plays a crucial role in plate tectonics.

* Transition Zone: Located between the asthenosphere and the lower mantle, this zone is marked by significant changes in mineral composition and density.

2. Lower Mantle:

* Mesosphere: This is the solid, dense, and relatively stable layer beneath the transition zone, extending to the core-mantle boundary at a depth of about 2,900 km (1,800 miles). The extreme pressure in this layer keeps the material solid, despite its high temperature.

Key Characteristics of Each Layer:

| Layer | Key Characteristics |

|---|---|

| Lithosphere | Rigid, composed of crust and uppermost mantle, broken into tectonic plates |

| Asthenosphere | Partially molten, plastic, allows for plate movement |

| Transition Zone | Mineral changes, density increase |

| Mesosphere | Solid, dense, stable |

It's important to note that the mantle's layers are not distinct boundaries but rather gradual transitions in composition, temperature, and pressure.