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Why is the ocean floor near a spreading centre younger than ocean floor farther away?

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World map highlighting major features of the ocean basins, including trenches, ridges, basins, and plateaus labeled throughout the Pacific, Atlantic, Indian, Southern, and Arctic Oceans. Continents are shown with shaded terrain, and prominent undersea features such as the Mid-Atlantic Ridge, Mariana Trench, and Kerguelen Plateau are marked across the map. — ocean basin Major features of the ocean basins.

The ocean floor near a spreading centre is younger than the ocean floor farther away because of the continuous process of seafloor spreading.

At these divergent plate boundaries, tectonic plates move apart, creating a gap that allows magma to well up from the mantle. As this molten material cools, it solidifies to form new oceanic crust directly at the ridge axis.123

As the plates continue to diverge, this newly formed crust is pushed laterally away from the spreading centre, making room for even newer material to emerge and solidify in its place. Consequently, the crust located at the ridge is the most recently formed, while the crust found at greater distances has been moving away from the source for a longer period, resulting in a progressive increase in age as one moves away from the mid-ocean ridge system.43