The layer that surrounds the Earth's center is called the mantle.

Here's a breakdown of the Earth's layers:

* Inner Core: Solid, mostly iron and nickel.

* Outer Core: Liquid, also mostly iron and nickel.

* Mantle: The thickest layer, mostly solid rock, but behaves like a very viscous fluid over long periods.

* Crust: The thin, outermost layer, composed of various types of rock.

Let me know if you have any more questions about the Earth's structure!