Seabed
Marine habitats |
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Coastal habitats |
Ocean surface |
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Open ocean |
Sea floor |
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The structure of the seabed of the global ocean is governed by
Most of the seabed throughout the world's oceans is covered in layers of
Features of the seabed are governed by the physics of sediment transport and by the biology of the creatures living in the seabed and in the ocean waters above. Physically, seabed sediments often come from the erosion of material on land and from other rarer sources, such as volcanic ash. Sea currents transport sediments, especially in shallow waters where tidal energy and wave energy cause resuspension of seabed sediments. Biologically, microorganisms living within the seabed sediments change seabed chemistry. Marine organisms create sediments, both within the seabed and in the water above. For example, phytoplankton with silicate or calcium carbonate shells grow in abundance in the upper ocean, and when they die, their shells sink to the seafloor to become seabed sediments.
Human impacts on the seabed are diverse. Examples of human effects on the seabed include exploration, plastic pollution, and exploitation by mining and
Structure


Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources. The structure of the oceans, starting with the continents, begins usually with a
The
Deep ocean water is divided into layers or zones, each with typical features of salinity, pressure, temperature and marine life, according to their depth. Lying along the top of the abyssal plain is the abyssal zone, whose lower boundary lies at about 6,000 m (20,000 ft). The hadal zone – which includes the oceanic trenches, lies between 6,000 and 11,000 metres (20,000–36,000 ft) and is the deepest oceanic zone.[2][3]
Depth below seafloor
Depth below seafloor is a
- Different seabeds in the world's oceans
-
gravel seabed in Italy
-
white sand seabed in Mexico
-
sand seabed in Greece
-
hydrothermal vents
Sediments

Sediments in the seabed vary in origin, from eroded land materials carried into the ocean by rivers or wind flow, waste and decompositions of sea creatures, and precipitation of chemicals within the sea water itself, including some from outer space. There are four basic types of sediment of the sea floor:
- Terrigenous (also lithogenous) describes the sediment from continents eroded by rain, rivers, and glaciers, as well as sediment blown into the ocean by the wind, such as dust and volcanic ash.
- Biogenous material is the sediment made up of the hard parts of sea creatures, mainly phytoplankton, that accumulate on the bottom of the ocean.
- Hydrogenous sediment is material that precipitates in the ocean when oceanic conditions change, or material created in hydrothermal vent systems.
- Cosmogenous sediment comes from extraterrestrial sources.[6]
Terrigenous and biogenous

Terrigenous sediment is the most abundant sediment found on the seafloor. Terrigenous sediments come from the continents. These materials are eroded from continents and transported by wind and water to the ocean. Fluvial sediments are transported from land by rivers and glaciers, such as clay, silt, mud, and glacial flour. Aeolian sediments are transported by wind, such as dust and volcanic ash.[7]
Biogenous sediment is the next most abundant material on the seafloor. Biogenous sediments are biologically produced by living creatures. Sediments made up of at least 30% biogenous material are called "oozes." There are two types of oozes: Calcareous oozes and Siliceous oozes. Plankton grow in ocean waters and create the materials that become oozes on the seabed. Calcareous oozes are predominantly composed of calcium shells found in phytoplankton such as coccolithophores and zooplankton like the foraminiferans. These calcareous oozes are never found deeper than about 4,000 to 5,000 meters because at further depths the calcium dissolves.[8] Similarly, Siliceous oozes are dominated by the siliceous shells of phytoplankton like diatoms and zooplankton such as radiolarians. Depending on the productivity of these planktonic organisms, the shell material that collects when these organisms die may build up at a rate anywhere from 1 mm to 1 cm every 1000 years.[8]
Hydrogenous and cosmogenous

Hydrogenous sediments are uncommon. They only occur with changes in oceanic conditions such as temperature and pressure. Rarer still are cosmogenous sediments. Hydrogenous sediments are formed from dissolved chemicals that precipitate from the ocean water, or along the mid-ocean ridges, they can form by metallic elements binding onto rocks that have water of more than 300 °C circulating around them. When these elements mix with the cold sea water they precipitate from the cooling water.[8] Known as manganese nodules, they are composed of layers of different metals like manganese, iron, nickel, cobalt, and copper, and they are always found on the surface of the ocean floor.[8]
Cosmogenous sediments are the remains of space debris such as comets and asteroids, made up of silicates and various metals that have impacted the Earth.[9]
Size classification

Another way that sediments are described is through their descriptive classification. These sediments vary in size, anywhere from 1/4096 of a mm to greater than 256 mm. The different types are: boulder, cobble, pebble, granule, sand, silt, and clay, each type becoming finer in grain. The grain size indicates the type of sediment and the environment in which it was created. Larger grains sink faster and can only be pushed by rapid flowing water (high energy environment) whereas small grains sink very slowly and can be suspended by slight water movement, accumulating in conditions where water is not moving so quickly.[11] This means that larger grains of sediment may come together in higher energy conditions and smaller grains in lower energy conditions.
Benthos

Many organisms adapted to deep-water pressure cannot survive in the upper parts of the
Because light is
Topography

Seabed topography (ocean topography or marine topography) refers to the shape of the land (topography) when it interfaces with the ocean. These shapes are obvious along coastlines, but they occur also in significant ways underwater. The effectiveness of marine habitats is partially defined by these shapes, including the way they interact with and shape ocean currents, and the way sunlight diminishes when these landforms occupy increasing depths. Tidal networks depend on the balance between sedimentary processes and hydrodynamics however, anthropogenic influences can impact the natural system more than any physical driver.[18]
Marine topographies include
The mass of the oceans is approximately 1.35×1018
Features

Each region of the seabed has typical features such as common sediment composition, typical topography, salinity of water layers above it, marine life, magnetic direction of rocks, and sedimentation. Some features of the seabed include flat abyssal plains, mid-ocean ridges, deep trenches, and hydrothermal vents.
Seabed topography is flat where layers of sediments cover the tectonic features. For example, the
Where the seafloor is actively spreading and sedimentation is relatively light, such as in the northern and eastern
Other seabed environments include hydrothermal vents, cold seeps, and shallow areas. Marine life is abundant in the
Human impact
Exploration
The seabed has been explored by submersibles such as
Plastic pollution
In 2020 scientists created what may be the first scientific estimate of how much
Exploitation

As of July 2024[update], only exploratory licenses have been issued, with no commercial-scale deep sea mining operations yet. The
Deep sea mining is also possible in the exclusive economic zone (EEZ) of countries, such as Norway, where it has been approved.[33] In 2022, the Cook Islands Seabed Minerals Authority (SBMA) granted three exploration licenses for cobalt-rich polymetallic nodules within their EEZ.[34] Papua New Guinea was the first country to approve a deep sea mining permit for the Solwara 1 project, despite three independent reviews highlighting significant gaps and flaws in the environmental impact statement.[35]
The most common commercial model of deep sea mining proposed involves a caterpillar-track hydraulic collector and a riser lift system bringing the harvested ore to a production support vessel with dynamic positioning, and then depositing extra discharge down the water column. Related technologies include robotic mining machines, as surface ships, and offshore and onshore metal refineries.[36][37] Wind farms, solar energy, electric vehicles, and battery technologies use many of the deep-sea metals.[36] Electric vehicle batteries are the main driver of the critical metals demand that incentivizes deep sea mining.[citation needed]
The
In art and culture
Some children's play songs include elements such as "There's a hole at the bottom of the sea", or "A sailor went to sea... but all that he could see was the bottom of the deep blue sea".
On and under the seabed are archaeological sites of historic interest, such as shipwrecks and sunken towns. This underwater cultural heritage is protected by the
See also
- Bottom trawling – Fishing method by towing a net along the seafloor
- Demersal fish – Fish that live and feed on or near the bottom of seas or lakes
- Human outpost – Human habitats located in environments inhospitable for humans
- International waters – Water outside of national jurisdiction
- Manganese nodule – Mineral concretion on the sea bottom made of concentric layers of iron/manganese hydroxides
- Methane clathrate – Methane-water lattice compound
- Nepheloid layer – Layer of water in deep sea
- New Zealand foreshore and seabed controversy – Indigenous rights controversy
- Offshore geotechnical engineering – Sub-field of engineering concerned with human-made structures in the sea
- Petrological Database of the Ocean Floor (PetBD)
- Plate tectonics – Movement of Earth's lithosphere
- Research vessel – Ship or boat designed, modified, or equipped to carry out research at sea
- Seabed characterization– Partitioning of a seabed acoustic image into discrete physical entities or classes
- Seafloor mapping– Study of underwater depth of lake or ocean floors
- Seafloor massive sulfide deposits – Mineral deposits from seafloor hydrothermal vents
- Sediment Profile Imagery (SPI) – Technique for photographing the interface between the seabed and the overlying water
References
- ISBN 978-0-321-59779-3.
- ^ "Open Ocean – Oceans, Coasts, and Seashores". National Park Service. Retrieved 13 October 2021.
- ^ NOAA. "Ocean floor features". National Oceanic and Atmospheric Administration. Retrieved 13 October 2021.
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we follow Ocean Drilling Program (ODP) meters below seafloor (mbsf) convention
- ISBN 978-0-521-85485-6. Retrieved 11 June 2010.
metres below the seafloor (mbsf)
- ^ ISBN 978-1-4051-8734-3.
- ISBN 978-1-4051-8734-3.
- ^ a b c d "The Bottom of the Ocean," Marine Science
- ^ "Types of Marine Sediments", Article Myriad
- ^ Grobe, Hannes; Kiekmann, Bernhard; Hillenbrand, Claus-Dieter. "The memory of polar oceans" (PDF). AWI: 37–45.
- ^ Tripati, Aradhna, Lab 6-Marine Sediments, Marine Sediments Reading, E&SSCI15-1, UCLA, 2012
- ^ a b Benthos from the Census of Antarctic Marine Life website
- ^ US Department of Commerce, National Oceanic and Atmospheric Administration. "How does pressure change with ocean depth?". oceanservice.NOAA.gov.
- ^ Haeckel, E. 1891. Plankton-Studien. Jenaische Zeitschrift für Naturwissenschaft 25 / (Neue Folge) 18: 232–336. BHL.
- Perseus Project.
- ^ "North American Benthological Society website". Archived from the original on 2008-07-05. Retrieved 2008-08-16.
- ^ Nehring, S. & Albrecht, U. (1997). Benthos und das redundant Benton: Neologismen in der deutschsprachigen Limnologie. Lauterbornia 31: 17-30, [1].
- ^ Giovanni Coco, Z. Zhou, B. van Maanen, M. Olabarrieta, R. Tinoco, I. Townend. Morphodynamics of tidal networks: Advances and challenges. Marine Geology Journal. 1 December 2013.
- ^ Sandwell, D. T.; Smith, W. H. F. (2006-07-07). "Exploring the Ocean Basins with Satellite Altimeter Data". NOAA/NGDC. Retrieved 2007-04-21.
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- S2CID 210979539. Retrieved 13 October 2021.
- ^ a b "The Discovery of Hydrothermal Vents". Woods Hole Oceanographic Institution. 11 June 2018. Retrieved 13 October 2021.
- ISBN 978-3-662-05127-6.
- ^ "Ocean Surface Topography". Science Mission Directorate. 31 March 2010. Retrieved 13 October 2021.
- ^ May, Tiffany (7 October 2020). "Hidden Beneath the Ocean's Surface, Nearly 16 Million Tons of Microplastic". The New York Times. Retrieved 30 November 2020.
- ^ "14 million tonnes of microplastics on sea floor: Australian study". phys.org. Retrieved 9 November 2020.
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- ^ "Exploration Contracts". International Seabed Authority. 17 March 2022. Retrieved 31 July 2024.
- ^ "Deep-sea mining's future still murky as negotiations end on mixed note". Mongabay. 2 April 2024.
- ^ Kuo, Lily (October 19, 2023). "China is set to dominate the deep sea and its wealth of rare metals". Washington Post. Retrieved 2024-02-14.
- ^ "Greenpeace responds to Norway's proposal to licence first Arctic areas for deep sea mining". 26 June 2024.
- ^ "Cook Islands Seabed Minerals Authority - Map". Archived from the original on 2022-06-30. Retrieved 2022-07-06.
- ^ "Campaign Reports | Deep Sea Mining: Out Of Our Depth". Deep Sea Mining: Out Of Our Depth. 2011-11-19. Archived from the original on 2019-12-13. Retrieved 2021-09-06.
- ^ a b SPC (2013). Deep Sea Minerals: Deep Sea Minerals and the Green Economy Archived 2021-11-04 at the Wayback Machine. Baker, E., and Beaudoin, Y. (Eds.) Vol. 2, Secretariat of the Pacific Community
- ^ "Breaking Free From Mining" (PDF). Archived from the original (PDF) on 2021-12-23.
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- ^ Rosenbaum, Helen (November 2011). "Out of Our Depth: Mining the Ocean Floor in Papua New Guinea". Deep Sea Mining Campaign. MiningWatch Canada, CELCoR, Packard Foundation. Archived from the original on 13 December 2019. Retrieved 2 May 2020.
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- ^ "Google, BMW, Volvo, and Samsung SDI sign up to WWF call for temporary ban on deep-sea mining". Reuters. 2021-03-31. Archived from the original on 2021-09-06. Retrieved 2021-09-06.
- ^ "SPC-EU Deep Sea Minerals Project - Home". dsm.gsd.spc.int. Archived from the original on 2021-09-06. Retrieved 2021-09-06.
- ^ "The Environmental Protection Authority (EPA) has refused an application by Chatham Rock Phosphate Limited (CRP)". Deepwater group. 2015. Archived from the original on 2016-01-24. Retrieved 6 September 2021.
- ^ John J. Gurney, Alfred A. Levinson, and H. Stuart Smith (1991) Marine mining of diamonds off the West Coast of Southern Africa, Gems & Gemology, p. 206
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Further reading
- Roger Hekinian: Sea Floor Exploration: Scientific Adventures Diving into the Abyss. Springer, 2014. ISBN 978-3-319-03203-0(eBook)
- Stéphane Sainson: Electromagnetic Seabed Logging. A new tool for geoscientists. Springer, 2016. ISBN 978-3-319-45355-2(eBook)
External links
- Understanding the Seafloor presentation from Cosee – the Center for Ocean Sciences Educational Excellence.
- Ocean Explorer (www.oceanexplorer.noaa.gov) – Public outreach site for explorations sponsored by the Office of Ocean Exploration.
- NOAA, Ocean Explorer Gallery, Submarine Ring of Fire 2006 Gallery, Submarine Ring of Fire 2004 Gallery – A rich collection of images, video, audio and podcast.
- NOAA, Ocean Explorer YouTube Channel
- Submarine Ring of Fire, Mariana Arc – Explore the volcanoes of the Mariana Arc, Submarine Ring of Fire.
- Age of the Ocean Floor National Geophysical Data Center
- Astonishing deep sea life on TED (conference)