Seabed
The seabed is the bottom of the ocean, also called the seafloor. It covers the beds of all the oceans and is shaped by plate tectonics. In the deep ocean, the seabed forms the flat abyssal plains. Mid‑ocean ridges run along the centers of the oceans where new seabed is created. From the abyssal plain the seabed rises toward the continents, passing through the continental rise, the continental slope, and the continental shelf.
Depth below seafloor is a term scientists use to measure how far down a sample goes into the seabed. The community of plants and animals living on or in the seabed is called the benthos.
Most of the seabed is covered with sediments. These sediments come from different sources and can be grouped as terrigenous (from land), biogenous (from living organisms), hydrogenous (chemical), and cosmogenous (space debris). Sediments also vary in size from tiny clay to large boulders. The movement of sediments is influenced by water currents and by the life in the seabed and in the water above. Erosion from land, rivers, and the breakdown of sea creatures all add material to the seabed. Shells from phytoplankton and other organisms sink to the bottom and become part of the sediments.
Biogenous sediments include ooze, which is made mostly from the shells of tiny plankton. Calcareous ooze is rich in calcium carbonate, while siliceous ooze is rich in silica. Calcareous ooze cannot form at great depths because the calcium dissolves. The rate at which these shells accumulate is slow, often millimeters to centimeters per thousand years. Hydrogenous sediments form in special chemical conditions, and cosmogenous sediments come from space, including tiny particles of cosmic dust and, in some places, manganese nodules that gather metals on the seabed.
The seabed features a variety of landscapes. There are underwater mountain ranges called mid-ocean ridges, deep trenches, and volcanic vents called hydrothermal vents. Around vents, life can thrive in the dark, relying on chemical energy instead of sunlight. Seamounts, coral reefs, and brine pools are other seabed features. The oceans are vast and deep, with the seabed spanning many different environments.
Benthos relies on two energy sources. In shallow waters, light supports the food web, but in the deep sea, energy mainly comes from organic matter that sinks from above. Many deep-sea organisms are scavengers or detritivores and are adapted to high pressure.
Submersibles, underwater cameras, and satellite measurements help scientists study the seabed. Satellite maps of the ocean surface now help researchers understand the sea floor, including its topography.
Plastic pollution has reached the seabed. A study near Australia suggested the seafloor contains millions of tons of microplastics, varying by location and seabed slope.
Deep-sea mining looks at extracting metals from the seabed, especially from nodules on the abyssal plain. The Clarion–Clipperton Zone holds large nodule deposits with metals like copper, nickel, cobalt, and manganese. As of recent years, only exploratory licenses have been granted, and no large-scale mining is underway. The process is regulated by the International Seabed Authority, with ongoing debate about environmental risks to deep-sea ecosystems. Some countries are exploring mining within their exclusive economic zones, which has sparked debate and regulatory work.
Underwater cultural heritage, such as shipwrecks and sunken towns, is protected by UNESCO to prevent looting and damage.
In short, the seabed is a diverse and dynamic part of the ocean, built by geology and life, hosting unique ecosystems, and increasingly the focus of scientific study and consideration of human activities.
This page was last edited on 2 February 2026, at 09:22 (CET).