Magma ocean

Imagine that the inside of the Earth is very hot and liquidy, like melted cheese on pizza. This melted rock is called magma, and sometimes it comes out of the Earth through volcanoes.

But a long time ago, when the Earth was first formed, it was so hot that the whole planet was like a big ball of magma. It was too hot for any rocks to form on the surface.

As the Earth cooled down over millions of years, the magma started to harden and form a surface crust. But underneath that crust there was still a lot of melted rock.

This big, hot, liquidy layer is called the magma ocean. It's like a giant pot of magma that stretches all the way around the Earth's core. Scientists think it lasted for millions of years before the Earth cooled down enough for the magma to solidify into the rocky layers we have today.

So basically, the magma ocean is like a really hot soup that used to cover the whole Earth a long time ago.