How Does Igneous Rocks Used to Be Liquid! | SciShow Kids Work?

Igneous rocks used to be molten liquid, just like how chocolate sauce turns into a solid candy bar when it cools down.

Imagine you have a big pot of hot soup, that's like molten rock inside the Earth. It’s very, very hot and runny. Now, if you take that pot out of the stove and let it cool, the soup gets thicker and eventually turns into a solid. That’s exactly what happens with igneous rocks: when molten rock cools down, it becomes hard and forms a rock.

Sometimes, the hot liquid cools slowly deep inside the Earth, like soup cooling on the table. This makes big, smooth crystals, like in granite.

Other times, the hot liquid comes out of volcanoes and cools quickly, like when you pour hot soup onto a cold plate. It becomes hard fast, making small or no crystals, like in obsidian, which is shiny and black.

So, even though igneous rocks look solid now, they used to be like hot, runny soup, just really, really hot!