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Why does sediment tend to be thinnest on oceanic ridges?

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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.

Sediment is thinnest on oceanic ridges because these areas are the sites of active seafloor spreading, where new oceanic crust is constantly being formed.12

At the ridge crests, fresh basaltic lavas are exposed, meaning the seafloor there is geologically youngest. As the tectonic plates move away from these spreading centres, the crust ages and is progressively buried by accumulating marine sediment. Consequently, sediment thickness increases with the age of the crust and the distance from the ridge crest. Because the ridge crests represent the most recently created seafloor, they have had the least amount of time to accumulate sedimentary deposits.12