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62-463: The Zone is the area comprising the territories of the states and their respective continental shelves and Exclusive Economic Zones (EEZ); "Territory" means the land territory, internal waters , territorial sea , archipelagic waters , the seabed and the sub-soil thereof and the airspace above them. The treaty includes a protocol under which the five nuclear-weapon states recognized by the Treaty on

124-701: A sediment core , is known as the "depth below seafloor". The ecological environment of the seabed and the deepest waters are collectively known, as a habitat for creatures, as the " benthos ". Most of the seabed throughout the world's oceans is covered in layers of marine sediments . Categorized by where the materials come from or composition, these sediments are classified as either: from land ( terrigenous ), from biological organisms (biogenous), from chemical reactions (hydrogenous), and from space (cosmogenous). Categorized by size, these sediments range from very small particles called clays and silts , known as mud, to larger particles from sand to boulders . Features of

186-455: A continental shelf differs significantly from the geological definition. UNCLOS states that the shelf extends to the limit of the continental margin , but no less than 200 nmi (370 km; 230 mi) and no more than 350 nmi (650 km; 400 mi) from the baseline . Thus inhabited volcanic islands such as the Canaries , which have no actual continental shelf, nonetheless have

248-832: A distance where the depth of waters admitted of resource exploitation were claimed by the marine nations that signed the Convention on the Continental Shelf drawn up by the UN's International Law Commission in 1958. This was partly superseded by the 1982 United Nations Convention on the Law of the Sea (UNCLOS). The 1982 convention created the 200 nautical miles (370 km; 230 mi) exclusive economic zone, plus continental shelf rights for states with physical continental shelves that extend beyond that distance. The legal definition of

310-464: A few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m (460 ft); this is likely a hallmark of past ice ages, when sea level was lower than it is now. The continental slope is much steeper than the shelf; the average angle is 3°, but it can be as low as 1° or as high as 10°. The slope is often cut with submarine canyons . The physical mechanisms involved in forming these canyons were not well understood until

372-491: A globe-spanning mid-ocean ridge system, as well as undersea volcanoes , oceanic trenches , submarine canyons , oceanic plateaus and abyssal plains . The mass of the oceans is approximately 1.35 × 10   metric tons , or about 1/4400 of the total mass of the Earth. The oceans cover an area of 3.618 × 10  km with a mean depth of 3,682 m, resulting in an estimated volume of 1.332 × 10  km . Each region of

434-404: A legal continental shelf, whereas uninhabitable islands have no shelf. Seabed 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 plate tectonics . Most of the ocean is very deep, where the seabed is known as

496-501: A rate anywhere from 1 mm to 1 cm every 1000 years. 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

558-402: Is absorbed before it can reach deep ocean water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain ; most organisms in the benthic zone are scavengers or detritivores . Seabed topography ( ocean topography or marine topography ) refers to

620-434: Is a vertical coordinate used in geology, paleontology , oceanography , and petrology (see ocean drilling ). The acronym "mbsf" (meaning "meters below the seafloor") is a common convention used for depths below the seafloor. 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

682-399: Is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea . Much of these shelves were exposed by drops in sea level during glacial periods . The shelf surrounding an island is known as an insular shelf . The continental margin , between the continental shelf and the abyssal plain , comprises a steep continental slope, surrounded by

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744-477: Is abundant in the deep sea around hydrothermal vents . Large deep sea communities of marine life have been discovered around black and white smokers – vents emitting chemicals toxic to humans and most vertebrates . This marine life receives its energy both from the extreme temperature difference (typically a drop of 150 degrees) and from chemosynthesis by bacteria . Brine pools are another seabed feature, usually connected to cold seeps . In shallow areas,

806-590: Is controversial. Environmental advocacy groups such as Greenpeace and the Deep Sea Mining Campaign claimed that seabed mining has the potential to damage deep sea ecosystems and spread pollution from heavy metal-laden plumes. Critics have called for moratoria or permanent bans. Opposition campaigns enlisted the support of some industry figures, including firms reliant on the target metals. Individual countries with significant deposits within their exclusive economic zones (EEZ's) are exploring

868-447: 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. Depth below seafloor

930-461: Is estimated that the global ocean floor holds more than 120 million tons of cobalt, five times the amount found in terrestrial reserves. As of July 2024 , only exploratory licenses have been issued, with no commercial-scale deep sea mining operations yet. The International Seabed Authority (ISA) regulates all mineral-related activities in international waters and has granted 31 exploration licenses so far: 19 for polymetallic nodules, mostly in

992-469: Is evidence that changing wind, rainfall, and regional ocean currents in a warming ocean are having an effect on some shelf seas. Improved data collection via Integrated Ocean Observing Systems in shelf sea regions is making identification of these changes possible. Continental shelves teem with life because of the sunlight available in shallow waters, in contrast to the biotic desert of the oceans' abyssal plain . The pelagic (water column) environment of

1054-414: Is not moving so quickly. This means that larger grains of sediment may come together in higher energy conditions and smaller grains in lower energy conditions. Benthos (from Ancient Greek βένθος ( bénthos )  'the depths [of the sea]'), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river , lake , or stream , also known as

1116-480: 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

1178-561: 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

1240-482: The Persian Gulf . The average width of continental shelves is about 80 km (50 mi). The depth of the shelf also varies, but is generally limited to water shallower than 100 m (330 ft). The slope of the shelf is usually quite low, on the order of 0.5°; vertical relief is also minimal, at less than 20 m (66 ft). Though the continental shelf is treated as a physiographic province of

1302-437: The abyssal plain regions of the ocean are relatively flat and covered in many layers of sediments. Sediments in these flat areas come from various sources, including but not limited to: land erosion sediments from rivers, chemically precipitated sediments from hydrothermal vents, Microorganism activity, sea currents eroding the seabed and transporting sediments to the deeper ocean, and phytoplankton shell materials. Where

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1364-412: The abyssal plain . Seafloor spreading creates mid-ocean ridges along the center line of major ocean basins, where the seabed is slightly shallower than the surrounding abyssal plain. From the abyssal plain, the seabed slopes upward toward the continents and becomes, in order from deep to shallow, the continental rise , slope , and shelf . The depth within the seabed itself, such as the depth down through

1426-453: The benthic zone . This community lives in or near marine or freshwater sedimentary environments , from tidal pools along the foreshore , out to the continental shelf , and then down to the abyssal depths . Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column . The pressure difference can be very significant (approximately one atmosphere for every 10 metres of water depth). Because light

1488-463: The ocean , it is not part of the deep ocean basin proper, but the flooded margins of the continent. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, made of thick sedimentary wedges derived from long erosion of a neighboring continent. Active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to

1550-414: The 1960s. Continental shelves cover an area of about 27 million km (10 million sq mi), equal to about 7% of the surface area of the oceans. The width of the continental shelf varies considerably—it is not uncommon for an area to have virtually no shelf at all, particularly where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off

1612-809: The CCZ; 7 for polymetallic sulphides in mid-ocean ridges ; and 5 for cobalt-rich crusts in the Western Pacific Ocean . There is a push for deep sea mining to commence by 2025, when regulations by the ISA are expected to be completed. Deep sea mining is also possible in the exclusive economic zone (EEZ) of countries, such as Norway , where it has been approved. In 2022, the Cook Islands Seabed Minerals Authority (SBMA) granted three exploration licenses for cobalt-rich polymetallic nodules within their EEZ. Papua New Guinea

1674-751: The Meeting of the Commission for the Treaty on the SEANWFZ, the Ministers reviewed the progress on the implementation of the 2013-2017 Plan of Action to Strengthen the SEANWFZ Treaty, while reaffirming their commitment to preserve Southeast Asia as a Nuclear-Weapon Free Zone. The SEANWFZ treaty has a protocol that is open to signature by the five recognized nuclear-weapon states: China, France, Russia,

1736-687: The Non-Proliferation of Nuclear Weapons (NPT), namely China , the United States , France , Russia and the United Kingdom (who are also the five permanent members of the United Nations Security Council ) undertake to respect the Treaty and do not contribute to a violation of it by State parties. None of the nuclear-weapon states have signed this protocol. The groundwork of the establishment of

1798-594: The United Kingdom, and the United States. The protocol commits those states not to contribute to any violation of the treaty and not to use or threaten to use nuclear weapons within the zone. As of April 2015, none of the five has signed the SEANWFZ protocol, but in November 2011 they agreed with ASEAN states on steps that would enable them to do so. Continental shelves A continental shelf

1860-536: The amount of plastic thought – per Jambeck et al., 2015 – to currently enter the oceans annually. Deep sea mining is the extraction of minerals from the seabed of the deep sea . The main ores of commercial interest are polymetallic nodules , which are found at depths of 4–6 km (2.5–3.7 mi) primarily on the abyssal plain . The Clarion–Clipperton zone (CCZ) alone contains over 21 billion metric tons of these nodules, with minerals such as copper , nickel , and cobalt making up 2.5% of their weight. It

1922-485: The balance between sedimentary processes and hydrodynamics however, anthropogenic influences can impact the natural system more than any physical driver. Marine topographies include coastal and oceanic landforms ranging from coastal estuaries and shorelines to continental shelves and coral reefs . Further out in the open ocean, they include underwater and deep sea features such as ocean rises and seamounts . The submerged surface has mountainous features, including

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1984-706: The coast of Chile or the west coast of Sumatra . The largest shelf—the Siberian Shelf in the Arctic Ocean —stretches to 1,500 kilometers (930 mi) in width. The South China Sea lies over another extensive area of continental shelf, the Sunda Shelf , which joins Borneo , Sumatra, and Java to the Asian mainland. Other familiar bodies of water that overlie continental shelves are the North Sea and

2046-567: The coast; sand is limited to shallow, wave-agitated waters, while silt and clays are deposited in quieter, deep water far offshore. These accumulate 15–40 centimetres (5.9–15.7 in) every millennium, much faster than deep-sea pelagic sediments . "Shelf seas" are the ocean waters on the continental shelf. Their motion is controlled by the combined influences of the tides , wind-forcing and brackish water formed from river inflows ( Regions of Freshwater Influence ). These regions can often be biologically highly productive due to mixing caused by

2108-450: The cold sea water they precipitate from the cooling water. 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. 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. Another way that sediments are described

2170-420: The continental shelf constitutes the neritic zone , and the benthic (sea floor) province of the shelf is the sublittoral zone . The shelves make up less than 10% of the ocean, and a rough estimate suggests that only about 30% of the continental shelf sea floor receives enough sunlight to allow benthic photosynthesis. Though the shelves are usually fertile, if anoxic conditions prevail during sedimentation,

2232-465: The continental slope and the abyssal plain usually has a more gradual descent, and is called the continental rise , which is caused by sediment cascading down the continental slope. The mid-ocean ridge , as its name implies, is a mountainous rise through the middle of all the oceans, between the continents. Typically a rift runs along the edge of this ridge. Along tectonic plate edges there are typically oceanic trenches – deep valleys, created by

2294-428: The deep ocean floor, the abyssal plain . The continental shelf and the slope are part of the continental margin . The shelf area is commonly subdivided into the inner continental shelf , mid continental shelf , and outer continental shelf , each with their specific geomorphology and marine biology . The character of the shelf changes dramatically at the shelf break, where the continental slope begins. With

2356-418: The deep sea. The continental shelves are covered by terrigenous sediments ; that is, those derived from erosion of the continents. However, little of the sediment is from current rivers ; some 60–70% of the sediment on the world's shelves is relict sediment , deposited during the last ice age, when sea level was 100–120 m lower than it is now. Sediments usually become increasingly fine with distance from

2418-433: The deposits may over geologic time become sources for fossil fuels . The continental shelf is the best understood part of the ocean floor, as it is relatively accessible. Most commercial exploitation of the sea, such as extraction of metallic ore, non-metallic ore, and hydrocarbons , takes place on the continental shelf. Sovereign rights over their continental shelves down to a depth of 100 m (330 ft) or to

2480-582: The establishment of SEANWFZ. However, due to the political atmosphere at that time, including rivalries among the members and conflicts in the region and the Cold War , it was less feasible then to establish SEANWFZ. Thus the formal proposal for establishing a nuclear-free region was delayed until the 1990s, after the Cold War ended and conflicts were settled, and the member states renewed the denuclearization efforts. After conducting negotiations and finalizing

2542-410: The flatter continental rise , in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise 's gradient is intermediate between the gradients of the slope and

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2604-416: The foraminiferans. These calcareous oozes are never found deeper than about 4,000 to 5,000 meters because at further depths the calcium dissolves. 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

2666-524: The future Southeast Asian Nuclear-Weapon-Free Zone Treaty (SEANWFZ) was started on November 27, 1971, when the 5 original members of the Association of Southeast Asian Nations (ASEAN), Indonesia, Malaysia, Philippines, Singapore, and Thailand, met in Kuala Lumpur , Malaysia and signed the declaration on ASEAN's Zone of Peace, Freedom and Neutrality (ZOPFAN) . One of the targets of ASEAN was also

2728-444: The mantle circulation movement from the mid-ocean mountain ridge to the oceanic trench. Hotspot volcanic island ridges are created by volcanic activity, erupting periodically, as the tectonic plates pass over a hotspot. In areas with volcanic activity and in the oceanic trenches there are hydrothermal vents – releasing high pressure and extremely hot water and chemicals into the typically freezing water around it. Deep ocean water

2790-448: 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 continental shelf , continues to the continental slope – which is a steep descent into the ocean, until reaching the abyssal plain – a topographic plain , the beginning of the seabed, and its main area. The border between

2852-537: The sea water itself, including some from outer space. There are four basic types of sediment of the sea floor: 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. Biogenous sediment

2914-488: The seabed , and these satellite-derived maps are used extensively in the study and exploration of the ocean floor. In 2020 scientists created what may be the first scientific estimate of how much microplastic currently resides in Earth's seafloor , after investigating six areas of ~3 km depth ~300 km off the Australian coast. They found the highly variable microplastic counts to be proportionate to plastic on

2976-468: 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

3038-440: The seabed can host sediments created by marine life such as corals, fish, algae, crabs, marine plants and other organisms. The seabed has been explored by submersibles such as Alvin and, to some extent, scuba divers with special equipment. Hydrothermal vents were discovered in 1977 by researchers using an underwater camera platform. In recent years satellite measurements of ocean surface topography show very clear maps of

3100-404: 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,

3162-501: 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 dredging operations. To map

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3224-592: The seabed, ships use acoustic technology to map water depths throughout the world. Submersible vehicles help researchers study unique seabed ecosystems such as hydrothermal vents . Plastic pollution is a global phenomenon, and because the ocean is the ultimate destination for global waterways, much of the world's plastic ends up in the ocean and some sinks to the seabed. Exploitation of the seabed involves extracting valuable minerals from sulfide deposits via deep sea mining, as well as dredging sand from shallow environments for construction and beach nourishment . Most of

3286-411: The seafloor is actively spreading and sedimentation is relatively light, such as in the northern and eastern Atlantic Ocean , the original tectonic activity can be clearly seen as straight line "cracks" or "vents" thousands of kilometers long. These underwater mountain ranges are known as mid-ocean ridges . Other seabed environments include hydrothermal vents, cold seeps, and shallow areas. Marine life

3348-400: The shallower waters and the enhanced current speeds. Despite covering only about 8% of Earth's ocean surface area, shelf seas support 15–20% of global primary productivity . In temperate continental shelf seas, three distinctive oceanographic regimes are found, as a consequence of the interplay between surface heating, lateral buoyancy gradients (due to river inflow), and turbulent mixing by

3410-410: 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

3472-519: The shelf. Under the United Nations Convention on the Law of the Sea , the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs. The shelf usually ends at a point of increasing slope (called the shelf break ). The sea floor below the break is the continental slope . Below the slope is the continental rise , which finally merges into

3534-533: The subject. 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 UNESCO Convention on the Protection of

3596-412: The surface and the angle of the seafloor slope. By averaging the microplastic mass per cm , they estimated that Earth's seafloor contains ~14 million tons of microplastic – about double the amount they estimated based on data from earlier studies – despite calling both estimates "conservative" as coastal areas are known to contain much more microplastic pollution . These estimates are about one to two times

3658-459: The tides and to a lesser extent the wind. Indian Ocean shelf seas are dominated by major river systems, including the Ganges and Indus rivers. The shelf seas around New Zealand are complicated because the submerged continent of Zealandia creates wide plateaus. Shelf seas around Antarctica and the shores of the Arctic Ocean are influenced by sea ice production and polynya . There

3720-527: The treaty for SEANWFZ by an ASEAN working group, the SEANWFZ treaty finally signed by the heads of government from 10 ASEAN member states in Bangkok on December 15, 1995. The treaty took effect on 28 March 1997 after all but one of the member states have ratified it. It became fully effective on 21 June 2001, after the Philippines ratified it, effectively banning all nuclear weapons in the region. In 2014 at

3782-403: The water column. Related technologies include robotic mining machines, as surface ships, and offshore and onshore metal refineries. Wind farms, solar energy, electric vehicles , and battery technologies use many of the deep-sea metals. Electric vehicle batteries are the main driver of the critical metals demand that incentivizes deep sea mining. The environmental impact of deep sea mining

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3844-516: 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. 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

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