Here's why:

* Seafloor Spreading: Mid-ocean ridges are where new oceanic crust is created. Magma rises from the Earth's mantle, cools, and solidifies, pushing older crust away from the ridge.

* Continuous Formation: This process of seafloor spreading is ongoing, meaning that the rocks closest to the ridge are the newest, while those farther away are progressively older.

Therefore, the youngest rocks on the seafloor are found at the central axis of the mid-ocean ridges, where the newest magma is constantly erupting and solidifying.