Here's why:

* Plate Tectonics: The Earth's crust is made up of massive plates that constantly move. At mid-ocean ridges, these plates pull apart (diverge).

* Magma Upwelling: As the plates separate, magma from the Earth's mantle rises to the surface, creating new oceanic crust. This process is called seafloor spreading.

* Continuous Creation: Because magma is constantly being added at the ridges, the oceanic crust gets older as you move away from them.

So, the areas closest to the mid-ocean ridges represent the newest and youngest parts of the Earth's oceanic crust.