The imaginary line running down the middle of the Atlantic Ocean from the North Pole to the South Pole is called the Mid-Atlantic Ridge.

It's not just any line, though! It's a massive underwater mountain range that's actually a divergent plate boundary. This means that the Earth's tectonic plates are pulling apart here, causing magma to rise from the mantle and create new oceanic crust.

This process is what has formed the Atlantic Ocean over millions of years!