What environment leads to sediments being thickest in oceans?

Thick sediments in oceans are primarily found in areas adjacent to continental margins due to several geological processes. These margins serve as transects where sediments eroded from land are transported via rivers, currents, and other mechanisms into the ocean. As rivers reach the sea, they deposit large amounts of sediments, contributing to the overall thickness of sediment layers in these regions.

Furthermore, the continental shelf, which is the submerged border of a continent, provides a broad area where sediments can accumulate over time. The interactions of different sediment sources, such as river runoff, turbidite flows, and offshore sediment transport, lead to significant deposits, making these areas rich in sediment accumulation.

In contrast, environments with volcanic activity may generate volcanic ash and materials, but they do not generally lead to the thickest sediment layers compared to the sediment accumulation on continental margins. Young oceanic crust, while still accumulating sediment, tends to be thinner and underdeveloped in terms of sediment layering. Open ocean regions typically have lower sediment deposition rates, as they are far from terrestrial sediment sources. Thus, continental margins are the environments where sediments are thickest in oceans due to the combination of sediment supply and favorable conditions for accumulation.