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 is broken into tectonic plates that move and interact, causing earthquakes and volcanic activity.

* Asthenosphere: This is a soft, partially molten layer beneath the lithosphere. It is characterized by its ability to flow slowly over long periods, allowing tectonic plates to move.

* Transition Zone: This layer marks the boundary between the upper and lower mantle. It is characterized by changes in mineral composition and density.

2. Lower Mantle:

* Mesosphere: This is the thickest and densest layer of the mantle, extending to the outer core. It is a solid, but very hot and under immense pressure, making it behave like a viscous fluid.

Here's a breakdown of the key features of each layer:

| Layer | Description | Key Features |

|---|---|---|

| Lithosphere | Rigid, outermost layer | Composed of crust and uppermost mantle; broken into tectonic plates; responsible for plate tectonics |

| Asthenosphere | Partially molten, soft layer | Allows tectonic plates to move; responsible for mantle convection |

| Transition Zone | Boundary between upper and lower mantle | Changes in mineral composition and density |

| Mesosphere | Thickest and densest layer | Solid, but behaves like a viscous fluid due to immense pressure and heat |

It's important to note that these layers are not distinct boundaries, but rather zones with gradual changes in properties. The exact depth and characteristics of these layers can vary depending on location and geological context.