The outer core is not made of rock. It's made of liquid iron and nickel, with smaller amounts of other elements like sulfur, silicon, and oxygen.

Here's why:

* Temperature and Pressure: The outer core's extreme heat (around 4,500°C) and immense pressure are far too high for traditional rocks to exist. These conditions melt even the toughest minerals.

* Density: The outer core's density is much higher than any known rock.

* Magnetic Field: The movement of the liquid iron and nickel generates Earth's magnetic field. This would be impossible if the outer core were solid.

So, while the outer core is often referred to as a "layer," it's not in the same sense as the solid layers of the Earth's mantle and crust.