Marine geology

Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, geochemical, sedimentological and paleontological investigations of the ocean floor and coastal zone. Marine geology has strong ties to geophysics and to physical oceanography.

Marine geological studies were of extreme importance in providing the critical evidence for sea floor spreading and plate tectonics in the years following World War II. The deep ocean floor is the last essentially unexplored frontier and detailed mapping in support of both military (submarine) objectives and economic (petroleum and metal mining) objectives drives the research.

Oceanic spreading
Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches.


A trench forms at the boundary where two tectonic plates meet

The Ring of Fire around the Pacific Ocean with its attendant intense volcanism and seismic activity poses a major threat for disastrous earthquakes, tsunamis and volcanic eruptions. Any early warning systems for these disastrous events will require a more detailed understanding of marine geology of coastal and island arc environments.

The study of littoral and deep sea sedimentation and the precipitation and dissolution rates of calcium carbonate in various marine environments has important implications for global climate change.

The discovery and continued study of mid-ocean rift zone volcanism and hydrothermal vents, first in the Red Sea and later along the East Pacific Rise and the Mid-Atlantic Ridge systems were and continue to be important areas of marine geological research. The extremophile organisms discovered living within and adjacent to those hydrothermal systems have had a pronounced impact on our understanding of life on Earth and potentially the origin of life within such an environment.

Oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They also are the deepest parts of the ocean floor.

The Mariana Trench (or Marianas Trench) is the deepest known submarine trench, and the deepest location in the Earth's crust itself. A subduction zone where the Pacific Plate is being subducted under the Philippine Sea Plate. The bottom of the trench is further below sea level than Mount Everest is above sea level.

See also


  • Erickson, Jon, 1996, Marine Geology: Undersea Landforms and Life Forms, Facts on File ISBN 0-8160-3354-4
  • Seibold, E. and W.H. Berger, 1994, The Sea Floor: An Introduction to Marine Geology, Springer-Verlag ISBN 0-387-56884-0

External links

Back-arc basin

Back-arc basins are geologic basins, submarine features associated with island arcs and subduction zones. They are found at some convergent plate boundaries, presently concentrated in the western Pacific Ocean. Most of them result from tensional forces caused by oceanic trench rollback (the oceanic trench is wandering in the seafloor direction) and the collapse of the edge of the continent. The arc crust is under extension or rifting as a result of the sinking of the subducting slab. Back-arc basins were initially a surprising result for plate tectonics theorists, who expected convergent boundaries to be zones of compression, rather than major extension. However, they are now recognized as consistent with this model in explaining how the interior of Earth loses heat.

Bathymetric chart

A bathymetric chart is the submerged equivalent of an above-water topographic map. Bathymetric charts are designed to present accurate, measurable description and visual presentation of the submerged terrain.

Bathymetric surveys and charts are more closely tied to the science of oceanography, particularly marine geology, and underwater engineering or other specialized purposes.

Bathymetric charts can also be converted to bathymetric profiles.


A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a type of smaller bay with a circular inlet and narrow entrance. A fjord is a particularly steep bay shaped by glacial activity.

A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may also be nested within each other; for example, James Bay is an arm of Hudson Bay in northeastern Canada. Some large bays, such as the Bay of Bengal and Hudson Bay, have varied marine geology.

The land surrounding a bay often reduces the strength of winds and blocks waves. Bays may have as wide a variety of shoreline characteristics as other shorelines. In some cases, bays have beaches, which "are usually characterized by a steep upper foreshore with a broad, flat fronting terrace". Bays were significant in the history of human settlement because they provided safe places for fishing. Later they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports.

Blue hole

A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock (limestone or coral reef). Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples can be found in South China Sea (Dragon Hole), Belize (Great Blue Hole), the Bahamas (Dean's Blue Hole), Guam, Australia (in the Great Barrier Reef), and Egypt (in the Red Sea).

Blue holes are distinguished from cenotes in that the latter are inland voids usually containing fresh groundwater rather than seawater.

Dean's Blue Hole

Dean's Blue Hole is a blue hole located in The Bahamas in a bay west of Clarence Town on Long Island and is the world's second deepest, after the Dragon Hole in the South China Sea, with a depth of 202 metres (663 ft).

Fundus (seabed)

The fundus is the seabed in a tidal river below low water mark. This can be owned by the foreshore owner (area between high and low water mark) and may require permission and rent, if used for laying a mooring or putting down crab or lobster pots.


The GeoRef database is a bibliographic database that indexes scientific literature in the geosciences, including geology. Coverage ranges from 1666 to the present for North American literature, and 1933 to the present for the rest of the world. It currently contains more than 2.8 million references. It is widely considered one of the preeminent literature databases for those studying the earth sciences.It is produced by the American Geosciences Institute, which was known as the American Geological Institute until October 2011.

"To maintain the database, GeoRef editor/indexers regularly scan more than 3,500 journals in 40 languages as well as new books, maps, and reports. They record the bibliographic data for each document and assign index terms to describe it. Each month between 6,000 and 9,000 new references are added to the database."Major areas of coverage by GeoRef include:

Areal geology

Economic geology

Engineering geology

Environmental geology

Extraterrestrial geology




Hydrogeology and hydrology

Marine geology and oceanography

Mathematical geology

Mineralogy and Crystallography





Structural geology

Surficial geologyPrint publications that correspond to GeoRef are Bibliography and Index of North American Geology; Bibliography of Theses in Geology; and the Geophysical Abstracts, Bibliography and Index of Geology Exclusive of North America.


In marine geology, a guyot (pronounced ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than 200 m (660 ft) below the surface of the sea. The diameters of these flat summits can exceed 10 km (6.2 mi). Guyots are most commonly found in the Pacific Ocean, but they have been identified in all the oceans except the Arctic Ocean.

Lamont–Doherty Earth Observatory

The Lamont–Doherty Earth Observatory (LDEO) is a research unit of Columbia University located on a 157-acre (64 ha) campus in Palisades, N.Y., 18 miles (29 km) north of Manhattan on the Hudson River.

Liu Guangding

Liu Guangding (simplified Chinese: 刘光鼎; traditional Chinese: 劉光鼎; pinyin: Liǘ Guāngdǐng; 29 December 1929 – 7 August 2018) was a Chinese geophysicist best known for his work in geophysics, marine geology and petroleum geology. He had been hailed as "Father of Chinese marine geology". He was a member of the 8th and 9th National Committee of the Chinese People's Political Consultative Conference.

Marine Geology (journal)

Marine Geology is a peer-reviewed scientific journal about marine geology published by Elsevier. About its scope the journal states "We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed.".

Marine and Petroleum Geology

Marine and Petroleum Geology is a peer-reviewed scientific journal covering marine and petroleum geology. It was established in 1984 and is published by Elsevier. The editor-in-chief is Massimo Zecchin (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale and (Max) Qinhong Hu (The University of Texas at Arlington).

Ocean Drilling Program

The Ocean Drilling Program (ODP) was a multinational effort to explore and study the composition and structure of the Earth's oceanic basins. ODP, which began in 1985, was the successor to the Deep Sea Drilling Project initiated in 1968 by the United States. ODP was an international effort with contributions of Australia, Germany, France, Japan, the United Kingdom and the ESF Consortium for Ocean Drilling (ECOD) including 12 further countries. The program used the drillship JOIDES Resolution on 110 expeditions (legs) to collect about 2000 deep sea cores from major geological features located in the ocean basins of the world. Drilling discoveries led to further questions and hypotheses, as well as to new disciplines in earth sciences such as the field of paleoceanography. In 2004 ODP transformed into the Integrated Ocean Drilling Program (IODP).

Oceanic basin

In hydrology, an oceanic basin may be anywhere on Earth that is covered by seawater but geologically ocean basins are large geologic basins that are below sea level. Geologically, there are other undersea geomorphological features such as the continental shelves, the deep ocean trenches, and the undersea mountain ranges (for example, the mid-Atlantic ridge and the Emperor Seamounts) which are not considered to be part of the ocean basins; while hydrologically, oceanic basins include the flanking continental shelves and shallow, epeiric seas.


Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the re-construction of past climate at various intervals. Paleoceanographic research is also intimately tied to paleoclimatology.

Pelagic sediment

Pelagic sediment or pelagite is a fine-grained sediment that accumulates as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist primarily of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton; clay-size siliciclastic sediment; or some mixture of these. Trace amounts of meteoric dust and variable amounts of volcanic ash also occur within pelagic sediments.

Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, and red clays.The composition of pelagic sediments is controlled by three main factors. The first factor is the distance from major landmasses, which affects their dilution by terrigenous, or land-derived, sediment. The second factor is water depth, which affects the preservation of both siliceous and calcareous biogenic particles as they settle to the ocean bottom. The final factor is ocean fertility, which controls the amount of biogenic particles produced in surface waters.


Sapropel (a contraction of ancient Greek words sapros and pelos, meaning putrefaction and mud, respectively) is a term used in marine geology to describe dark-coloured sediments that are rich in organic matter. Sapropels events occurs periodically (about every 21000 years) and are specific to the Mediterranean Sea. Organic carbon concentrations in sapropels commonly exceed 2% in weight.

Society for Sedimentary Geology

The Society for Sedimentary Geology is an international not-for-profit, scientific society based in Tulsa, Oklahoma. It is commonly referred to by its acronym SEPM, which refers to its former name, the Society of Economic Paleontologists and Mineralogists.

The Society’s reason for being is to disseminate scientific information on sedimentology, stratigraphy, paleontology, environmental sciences, marine geology, hydrogeology, and related specialties. Members benefit from both gaining and exchanging information pertinent to their geologic specialties. Information is dispersed via the publication of two major scientific journals, the Journal of Sedimentary Research (JSR) and PALAIOS, and the organization of technical conferences and short courses. It also publishes a monthly magazine for its members, The Sedimentary Record.

Terrigenous sediment

In oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, they are derived from terrestrial (as opposed to marine) environments. Consisting of sand, mud, and silt carried to sea by rivers, their composition is usually related to their source rocks; deposition of these sediments is largely limited to the continental shelf.Sources of terrigenous sediments include volcanoes, weathering of rocks, wind-blown dust, grinding by glaciers, and sediment carried by icebergs.

Terrigenous sediments are responsible for a significant amount of the salt in today's oceans. Over time rivers continue to carry minerals to the ocean but when water evaporates, it leaves the minerals behind. Since chlorine and sodium are not consumed by biological processes, these two elements constitute the greatest portion of dissolved minerals.

History of geology
Сomposition and structure
Historical geology
Ocean zones
Sea level


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