This layer is made up of various materials that have settled to the bottom of the ocean, including:

* Biogenic sediments: Shells, bones, and other remains of marine organisms

* Terrigenous sediments: Sand, silt, and clay eroded from land

* Cosmogenic sediments: Dust and debris from space

* Volcanic sediments: Ash and other materials from underwater volcanoes

The sediment layer can vary greatly in thickness and composition depending on location and oceanographic conditions.