Underneath the Earth's crust lies the mantle, a thick layer of mostly solid rock that makes up about 84% of Earth's volume. Here's a breakdown of the Earth's layers:

* Crust: The thin, outermost layer of Earth, composed of solid rock. It's like the skin of an apple.

* Mantle: The thick layer beneath the crust, composed of mostly solid rock but with a semi-molten layer called the asthenosphere. This layer is responsible for plate tectonics.

* Outer core: A liquid layer of iron and nickel. Its movement generates Earth's magnetic field.

* Inner core: A solid ball of iron and nickel, despite the intense heat and pressure.

The mantle can be further divided into:

* Lithosphere: The rigid outermost layer of Earth, composed of the crust and the uppermost part of the mantle.

* Asthenosphere: A partially molten layer within the upper mantle. It's like a soft, gooey layer that allows the tectonic plates to move.

* Mesosphere: The lower part of the mantle, which is solid and rigid.

So, while the crust is the outermost layer, the mantle is the largest and most significant layer beneath it, playing a crucial role in shaping our planet.