The layer of the Earth composed of liquid iron is the outer core.

Here's a breakdown of Earth's layers:

* Crust: The thin, outermost layer of solid rock.

* Mantle: A thick layer of mostly solid rock that is very hot and behaves like a very viscous fluid over long periods.

* Outer core: A liquid layer composed primarily of iron and nickel.

* Inner core: A solid ball of iron and nickel, extremely hot due to immense pressure.