Here's why:

* Seafloor Spreading: Mid-ocean ridges are where new oceanic crust is created through a process called seafloor spreading. Magma from the Earth's mantle rises to the surface, cools, and solidifies, forming new crust.

* Conveyor Belt: As new crust is created, it moves away from the ridge in both directions, like a giant conveyor belt. This movement carries the newly formed rock further away from the ridge.

* Age Gradient: Because the crust is constantly being generated at the ridge, the rocks closest to the center are the youngest. The rocks farther away from the ridge are older because they have been around for a longer time.

Let me know if you have any other questions!