* Mantle: This is the thickest layer, accounting for 84% of the Earth's volume. It's made up of mostly solid rock, but it's also very hot and under immense pressure. This allows the mantle to flow very slowly over geological timescales, a process called convection, which drives plate tectonics.
* Upper Mantle: The top portion of the mantle is called the lithosphere, which includes the Earth's crust. This is the rigid outer layer of the Earth.
* Lower Mantle: The lower portion of the mantle is hotter and under even more pressure, making it more fluid-like.
* Transition Zone: There's a thin zone separating the upper and lower mantle, characterized by a sudden change in mineral composition and density.
* D″ Layer: This is a mysterious and poorly understood layer right above the outer core. It's thought to be partially molten and play a role in plate tectonics.
So, the middle of the Earth, between the core and the surface, is primarily the mantle, which is divided into the upper and lower mantle and includes the transition zone and the D″ layer.
