Seafloor

The seafloor refers to the surface of the Earth's ocean basins, forming the bottom boundary of the marine environment. It begins at the shoreline and extends down to the deepest trenches, and it is composed of oceanic crust overlain by sediment derived from terrigenous, biological, and chemical sources, with variations in composition and texture across its features.

The major architectural zones are the continental margins (shelf, slope, rise) and the deep ocean floor (abyssal plain, volcanic seamounts, guyots, plate boundaries). Oceanic crust is primarily basaltic and overlain by sediments; pillow lavas and gabbro may be exposed in rises or mid-ocean ridges. Sediments vary from coarse sands and gravels on shelves to pelagic clays and calcareous or siliceous oozes on deep basins.

Tectonics drive seafloor structure: seafloor spreading at mid-ocean ridges creates new crust; subduction at trenches recycles crust; transform faults offset ridges. Hydrothermal vents and cold seeps create local habitats and fuel chemosynthetic communities.

Humans map and study the seafloor with sonar-based bathymetry, seismic reflection, and drilling programs. The seafloor hosts diverse ecosystems and serves as a repository of climate and geological records in sediment cores. It is also a source of resources, including hydrocarbons, minerals from seabed nodules and crusts, and fisheries hotspots, with significant environmental considerations related to disturbance and mining.