Here's why:

* Divergent plates are tectonic plates that are moving apart.

* This movement creates a gap, which allows magma from the Earth's mantle to rise and erupt, creating new oceanic crust.

* The newly formed crust pushes the plates further apart, and the process continues, building the mid-ocean ridge.

So, the formation of a mid-ocean ridge is directly linked to the separation of tectonic plates.