* New Ocean Floor Formation: Mid-ocean ridges are where new oceanic crust is formed. As magma rises and cools, it creates new seafloor, pushing older crust away from the ridge. This continuous process means the seafloor near the ridge is relatively young.

* Time for Sediment Accumulation: Young seafloor hasn't had as much time to accumulate sediment as older seafloor further away from the ridge. Sedimentation is a slow process.

* Ocean Currents: Mid-ocean ridges often have strong currents associated with them. These currents can prevent sediment from settling near the ridge and instead carry it away to deeper basins.

Additional Factors:

* Volcanic Activity: The volcanic activity at the ridge can produce large amounts of volcanic ash and debris. This can actually bury some sediment and make it difficult to accumulate.

* Hydrothermal Vents: Hydrothermal vents near the ridge release hot, mineral-rich water, which can inhibit sediment accumulation.

Summary: The combination of new seafloor formation, limited time for sediment accumulation, strong ocean currents, volcanic activity, and hydrothermal vents all contribute to the thinner sediment layers closer to the mid-ocean ridge.