From Wikiversity
Jump to navigation Jump to search
This is a detailed, photo-like view of Earth based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Credit: Robert Simmon and Marit Jentoft-Nilsen, NASA.

As geomorphology is the study of landforms, hydromorphology is the study of water forms. Water as with any fluid under the influence of forces like gravity takes on the shape of its container.

But, unlike landforms which show their shapes in the atmosphere subject to the reflection of sunlight, the underwater shape of the water form usually cannot be seen.

The image on the right is a detailed, photo-like view of Earth based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.


Various ways to divide the World Ocean are shown using a rotating series of maps. Credit: Quizimodo.

Def. On Earth one of the five large bodies of water separating the continents is called an ocean.

Pacific oceans[edit]

This is a map of the Pacific Ocean basin. Credit: National Geographic Society.
This is a globe view of the Pacific Ocean without any clouds. Credit: Hawaii Pacific University.

The map above shows the geomorphology of the bottom of the Pacific Ocean.

At the top of this resource is a satellite view of the Pacific Ocean with clouds. On the left is a globe view of the Pacific Ocean without clouds. The Pacific Ocean occupies nearly a complete hemisphere of the Draft:Earth.

Atlantic oceans[edit]

This is a map of the Atlantic Ocean floor. Credit: National Geographic Society.{{fairuse}}
This image was generated from the ETOPO2v2 (2006) database. Credit: NCEI (formerly NGDC), NESDIS, NOAA.{{free media}}

The geomorphology of the bottom of the Atlantic Ocean is shown on the right. This is a bathymetric sea floor map of both the North and South Atlantic Oceans with a vertical exaggeration that emphasizes the entire mid-Atlantic ridge and the detailed sharpness associated with all the continental shelves from the boundary with the Arctic Ocean to the boundary with the Southern Ocean.

On the left is that portion of the global map which contains the Atlantic Ocean. "These images were generated from the ETOPO2v2 (2006) database. ETOPO2v2 was created at NGDC from digital databases of seafloor and land elevations on a 2-minute latitude/longitude grid (1 minute of latitude = 1 nautical mile, or 1.852 km). Assumed illumination is from the west; shading is computed as a function of the east-west slope of the surface with a nonlinear exaggeration favoring low-relief areas. A Cylindrical Equidistant projection was used for the world image, which spans 360 degrees of longitude from 180 West eastward to 180 East; latitude coverage is from 90 degrees North to 90 degrees South. The resolution of the gridded data varies from true 2-minute for the Atlantic, Pacific, and Indian Ocean floors and all land masses to 5 minutes for the Arctic Ocean floor."[1]

Norwegian Sea[edit]

Bathymetric chart is of the Norwegian Sea and adjacent areas. Credit: Jens Eggvin, Harald Kismul and Svein Lygren.{{fairuse}}
The Vestfjorden with the mountains of the Lofoten archipelago seen from Løvøy Island in Steigen. Credit: Finn Rindahl.{{free media}}
The Norwegian Sea is outlined in red. Credit: .{{free media}}

Vågakaillen (942 m) is the taller of the two peaks in the centre of the image.[2][3][4]

The large volume of water in the Norwegian Sea with its large heat absorption capacity is more important as a source of Norway's mild winters than the Gulf Stream and its extensions.[5]

The International Hydrographic Organization defines the limits of the Norwegian Sea as follows:[6]

On the Northeast. A line joining the southernmost point of West Spitzbergen to North Cape of Bear Island, through this island to Cape Bull and thence on to North Cape in Norway (25°45'E).
On the Southeast. The West coast of Norway between North Cape and Cape Stadt (62°10'N 5°00'E).
On the South. From a point on the West coast of Norway in 61st parallel north (Latitude 61°00' North) along this parallel to Longitude 0°53' West thence a line to the NE extreme of Fuglö (62°21'N 6°15'W) and on to the East extreme of Gerpir (65°05'N 13°30'W) in Iceland.
On the West. The Southeastern limit of Greenland Sea [A line joining the southernmost point of West Spitzbergen to the Northern point of Jan Mayen Island, down the West coast of that island to its Southern extreme, thence a Line to the Eastern extreme of Gerpir (65°05'N 13°30'W) in Iceland].

The existing narrow shelf sea between Norway and Greenland began to widen and deepen.[7]

Settling of the shelf after the separation of the continents has resulted in landslides, such as the Storegga Slide about 8,000 years ago that induced a major tsunami.[7]

The coasts of the Norwegian Sea were shaped during the last Ice Age when large glaciers several kilometres high pushed into the land, forming fjords, removing the crust into the sea, and thereby extending the continental slopes, especially off the Norwegian coast along Helgeland and north to the Lofoten Islands.[7]

The Norwegian continental shelf is between 40 and 200 kilometres wide, and has a different shape from the shelves in the North Sea and Barents Sea: it contains numerous trenches and irregular peaks, which usually have an amplitude of less than 100 metres, but can reach up to 400 metres.[8] They are covered with a mixture of gravel, sand, and mud, and the trenches are used by fish as spawning grounds.[7]

Deeper into the sea, there are two deep basins separated by a low ridge (its deepest point at 3,000 m) between the Vøring Plateau and Jan Mayen island, where the southern basin is larger and deeper, with large areas between 3,500 and 4,000 metres deep; the northern basin is shallower at 3,200–3,300 metres, but contains many individual sites going down to 3,500 metres.[9]

Submarine thresholds and continental slopes mark the borders of these basins with the adjacent seas. To the south lies the European continental shelf and the North Sea, to the east is the Eurasian continental shelf with the Barents Sea. To the west, the Scotland-Greenland Ridge separates the Norwegian Sea from the North Atlantic. This ridge is on average only 500 metres deep, only in a few places reaching the depth of 850 metres. To the north lie the Jan Mayen Ridge and Mohns Ridge, which lie at a depth of 2,000 metres, with some trenches reaching depths of about 2,600 meters.[9]

North Atlantic[edit]

This is a bathymetric or hydrographic map of the North Atlantic ocean floor. Credit: U.S. Navy.

This map is a bathymetric or hydrographic map of the North Atlantic ocean floor as it exists today. This map is constructed from U.S. Navy data. The floor of the North Atlantic is elevated along the Mid Atlantic Rift from Iceland to well South of the Azores in the southern Atlantic. The Azores Plateau and the area surrounding it are shown. This is a under water depth map, and it is color coded by depth, brown is approximately 200 m, which would have been near to or above sea level during the last ice age.

North Sea[edit]

Warming climate exposed a vast continental shelf for humans to inhabit. Credit: William E. McNulty and Jerome N. Cookson, Simon Fitch and Vincent Gaffney, North Sea Palaeolandscapes Project.
The map labels North Sea continental shelf features. Credit: Offshore-technology.com.

"Eighteen thousand years ago, the seas around northern Europe were some 400 feet lower than today. Britain was not an island but the uninhabited northwest corner of Europe, and between it and the rest of the continent stretched frozen tundra. As the world warmed and the ice receded, deer, aurochs, and wild boar headed northward and westward. The hunters followed. Coming off the uplands of what is now continental Europe, they found themselves in a vast, low-lying plain."[10]

"Doggerland is now believed to have been settled by Mesolithic people, probably in large numbers, until they were forced out of it thousands of years later by the relentlessly rising sea. A period of climatic and social upheaval ensued until, by the end of the Mesolithic, Europe had lost a substantial portion of its landmass and looked much as it does today."[10]

"Based on seismic survey data gathered mostly by oil companies prospecting under the North Sea, [...] the contours [...] translate into gently rolling hills, wooded valleys, lush marshes, and lagoons."[10]

"In addition to the human jawbone, [there are] accumulated more than a hundred other artifacts —animal bones showing signs of butchery and tools made from bone and antler, among them an ax decorated with a zigzag pattern. Because [there are] coordinates of these finds, and because objects on the seabed tend not to move far from where erosion liberates them, [...] many come from a specific area of the southern North Sea that the Dutch call De Stekels (the Spines), characterized by steep seabed ridges."[10]

"The most rapid rises of sea level were on the order of three to six feet a century, but because of the variable topography of the land, the flooding would not have been even. In areas as flat as modern-day East Anglia, a six-foot rise could have shifted the coast inland by miles; in hillier places, less. Down in low-lying Doggerland, the rising sea turned inland lakes into estuaries."[10]

“There would have been huge population shifts. People who were living out in what is now the North Sea would have been displaced very quickly.”[11]

Celtic Sea[edit]

Bathymetric map is of the Celtic Sea and the Bay of Biscay. Credit: Eric Gaba.{{free media}}

The Celtic Sea is the area of the Atlantic Ocean off the south coast of Ireland bounded to the east by Saint George's Channel.[12]

The Celtic Sea receives its name from the Celtic heritage of the bounding lands to the north and east.[13] The name was first proposed by Ernest William Lyons Holt at a 1921 meeting in Dublin of fisheries experts from England, Wales, Ireland, Scotland and France.[13] The desire for a common name came to be felt because of the common marine biology, geology and hydrology of the area.[13] It was adopted in France before being common in the English-speaking countries.[13]

"[T]he name Celtic Sea is hardly known even to oceanographers."[14] It was adopted by marine biologists and oceanographers, and later by petroleum exploration firms.[15] It is named in a 1963 British atlas,[16]

"[W]hat British maps call the Western Approaches, and what the oil industry calls the Celtic Sea [...] certainly the residents on the western coast [of Great Britain] don't refer to it as such."[17]

The definition approved in 1974 by the UK Hydrographer of the Navy for use in Admiralty Charts was "bounded roughly by lines joining Ushant, Land's End, Hartland Point, Lundy Island, St. Govan's Head and Rosslare Harbour, thence following the Irish coast south to Mizen Head and then along the 200-metre isobath to approximately the latitude of Ushant."[18]

The International Hydrographic Organization defines the limits of the Celtic Sea as follows:[19]

On the North. The Southern limit of the Irish Sea [a line joining St David's Head to Carnsore Point], the South coast of Ireland, thence from Mizen Head a line drawn to a position 51° 0' N 11° 30' W.

On the West and South. A line from the position 51° 0' N 11° 30' W South to 49th parallel north (49°N), thence to latitude 46°30'N on the Western limit of the Bay of Biscay [a line joining Cape Ortegal to Penmarch Point], thence along that line to Penmarch Point.

On the East. The Western limit of the English Channel [a line joining Île Vierge to Land's End] and the Western limit of the Bristol Channel [a line joining Hartland Point to St. Govan's Head].

The seabed under the Celtic Sea is called the Celtic Shelf, part of the continental shelf of Europe. The northeast portion has a depth of between 90 and 100 m (300–330 ft), increasing towards Saint George's Channel. In the opposite direction, sand ridges pointing southwest have a similar height, separated by troughs approximately 50 m (160 ft) deeper. These ridges were formed by tidal effects when the sea level was lower. South of 50th parallel north (50°N) the topography is more irregular.[20]

North Atlantic Ridge[edit]

Surface of the Earth, 2 minute bathymetry/topography selection is sized at 45 degrees by 45 degrees. Credit: NCEI (formerly NGDC).

The image on the right shows the topography west of north western Africa out to the Mid-Atlantic Ridge. It clearly shows the impact the ridge had on the Azores microplate, breaking it into parts on either side of the ridge.

Iberian margins[edit]

This bathymetry map locates major seamounts between Madeira and Iberia. Credit: ELLA links.
The image shows the many islands, seamounts and ocean floor plateaus of the Iberian margins. Credit: Russell Wynn and Bryan Cronin.
The image shows the topography and bathymetry west of Iberia. Credit: C. Cramez.
Color shaded relief map of the southwest Iberian Margin includes land topography and bathymetry. Credit: Gerassimos A. Papadopoulos, Eulàlia Gràcia, Roger Urgeles, Valenti Sallares, Paolo Marco De Martini, Daniela Pantosti, Mauricio González, Ahmet C. Yalciner, Jean Mascle, Dimitris Sakellariou, Amos Salamon, Stefano Tinti, Vassilis Karastathis, Anna Fokaefs, Angelo Camerlenghi, Tatyana Novikova, and Antonia Papageorgiou.

In the images on the left, sea level during the last glaciation is likely at or above the yellow contour band. This appears to be the sea level delimiter in the second image down on the right.

Moroccan shelves[edit]

The image is a relative color-coded topographic map of the northern portion of the Moroccan shelf. Credit: Muawia Barazangi.
This elevation map shows the southern portion of the Moroccan shelf. Credit: Colleen McMahon, Macquarie University.

The first image on the right shows a currently submerged mountain range and associated islands directly in front of the Pillars of Hercules just further west. These may have been above sea level during the previous 50 kyrs ice age.

Azores microplates[edit]

The diagram shows the Azores current as it is deflected by the islands from the Gulf stream. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.
One of the 140 pyramids is imaged and observed by archeologists in the Madalena area of Pico Island, Azores. Credit: Carolina Matos.
The Azores are nine islands that occupy a triple junction between the North American, African and Eurasian Plate. It is a spreading center bound by the Mid-Atlantic Ridge on the west and the Terceira Rift on the NE and the East Azores Fracture Zone to the SE. Credit: Lourenço et al.
Map of the Azores archipelago and adjacent region shows all nine islands (western group: Flores and Corvo; central group: Terceira, Graciosa, Sao Jorge (SJ), Pico, and Faial; eastern group: Sao Miguel, and Santa Maria). Credit: Yang et al.
This image was taken from Flores of the island of Corvo to the north. Credit: C. Beier.

"Archaeologists from the Portuguese Association of Archaeological Research (APIA) have identified [a great variety of protohistoric pyramidal rock structures, some of them 13 meters tall] on Pico island that supports their belief that human occupation of the Azores predates the arrival of the Portuguese by many thousands of years."[21]

The "Madalena pyramidal structures, known by the locals as “maroiços,” are analogous to similar protohistoric structures found in Sicily, North Africa and the Canary islands which are known to have served ritual purposes."[21]

The diagram on the right shows the Azores current as it is deflected by the islands from the Gulf stream about 2014.

The second image down on the right shows the Azores as nine islands that occupy a triple junction between the North American, African and Eurasian Plate, a spreading center bound by the Mid-Atlantic Ridge on the west and the Terceira Rift on the NE and the East Azores Fracture Zone to the SE. From the structure shown, the microplate though thick has undergone extensive fracturing. If at one time it was at or near sea level, it could have blocked a significant portion of the Gulf stream, diverted a major portion toward northwest Africa, or diverted most of the stream north of Scotland into the Norwegian coast. The microplate likely broke apart and subsided in a west to east manner.

The second image on the left is a more geostructurally detailed topographic map of the entire Azores microplate. It clearly shows how the forming of the Mid-Atlantic Ridge underneath has torn the microplate apart along the ridge and approximately perpendicular to it. The orange to brown band is the 1,000 m to sea level band. White is currently above sea level. The yellow band is the 2,000 m to 1,000 m band. It surrounds much of the brown zone and suggests an almost square plateau.

The third image down on the left shows two rows or walls of similarly sized volcanic rock crossing the field of view like those used to make the Pico pyramids.

Canary Island seamount province[edit]

The Canary Island Seamount Province (CISP) comprises more than 100 seamounts. Credit: Paul van den Bogaard.

"The Canary Island Seamount Province forms a scattered hotspot track on the Atlantic ocean floor ~1300 km long and ~350 km wide, perpendicular to lithospheric fractures, and parallel to the NW African continental margin. New 40Ar/39Ar datings show that seamount ages vary from 133 Ma to 0.2 Ma in the central archipelago, and from 142 Ma to 91 Ma in the southwest."[22]

Shallow "mantle upwelling beneath the Atlantic Ocean basin off the NW African continental lithosphere flanks produced recurrent melting anomalies and seamounts from the Late Jurassic to Recent".[22]

Northwest African continental margin[edit]

The image shows a portion of the northwest African continental margin. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.

There is an apparently small continental shelf along the northwest African coast.

Mauritanian continental shelves[edit]

The image shows bathymetry of the Mauritanian and Senegambian continental shelves. Credit: Nadia Mhammdi, Maria Snoussi, Fida Medina and El Bachir Jaaidi.

The "sedimentary processes along the shelf are driven by long-term factors such as Quaternary glacial–interglacial periods and shelf morphology, and by short-term factors such as fluvial and aeolian sediment supply, local climate (temperature, rainfall and wind) and hydrodynamic conditions (tides, swell, longshore current, the Canary Current and upwelling)."[23]

Indian oceans[edit]

This is a map of the Indian Ocean floor. Credit: National Geographic Society.
The topographic/bathymetric map is of the Indian Ocean region. Credit: Cdc.

The image on the right shows a topographic map of the land at and above the Indian ocean level.

The bathymetric portion suggests some of the bottom features that provide the lower form of the ocean.

The image above is a more detailed map of the geomorphology of the bottom.

Southern oceans[edit]

This map shows the Southern Ocean floor around Antarctica. Credit: National Geographic Society.
Eddies in the Weddell Sea are near Antarctica. Credit: NASA.

The geomorphology that composes the bottom form of the Southern Ocean is shown on the left.

"The [image on the right] shows two large ocean circulation features, called eddies, at the northernmost edge of the sea ice pack in the Weddell Sea, off Antarctica. The eddy processes in this region play an important role in the circulation of the global ocean and the transportation of heat toward the pole. The ... image is the first wide-swath, multi-frequency, multi-polarization radar image ever processed. To date, no other spaceborne radar sensors have obtained swaths exceeding 100 kilometers (62 miles) in width."[24]

"The image is oriented approximately east-west, with a center location of around 56.6 degrees south latitude and 6.5 degrees west longitude. Image dimensions are 240 km by 350 km (149 miles by 218 miles)."[24]

"The ocean eddies have a clockwise (or cyclonic) rotation and are roughly 40 km to 60 km (25 miles to 37 miles) in diameter. The dark areas are new ice and the lighter green areas are small sea-ice floes that are swept along by surface currents; both of these areas are shown within the eddies and to the south of the eddies. First year seasonal ice, typically 0.5 meter to 0.8 meter (1.5 feet to 2.5 feet) thick, is shown in the darker green area in the lower right corner. The open ocean to the north is uniformly bright and appears blue, due to high winds making the surface rough. The colors in both images were obtained using the following radar channels: red is C-band vertically transmitted and vertically received; green is L-band horizontally transmitted and vertically received; and blue is L-band vertically transmitted and vertically received."[24]

Arctic ocean[edit]

Bathymetric map is of the Arctic Ocean. Credit: NOAA.{{free media}}
Although the map shows disputed areas, it also shows the Arctic Ocean floor. Credit: National Geographic Society.{{fairuse}}
Main bathymetric features of the Arctic Ocean, taken mainly from Weber 1983 'Maps of the Arctic Basin Sea Floor: A History of Bathymetry and its Interpretation' on a base of a screenshot taken from the NASA WorldWind software. Credit: Mikenorton.{{free media}}

The bottom features of the Arctic Ocean are displayed on the map above center, especially all continental shelves, the sea floor around the northern coast of Norway, Svalbard, and Novata Loklea at a smaller scale providing accurate detail. The other two maps provide naming.

Sea levels[edit]

This figure shows the change in annually averaged sea level at 23 geologically stable tide gauge sites with long-term records as selected. Credit: Robert A. Rohde.
This figure shows changes in sea level during the Holocene, the time following the end of the most recent glacial period, based on data from Fleming et al. 1998, Fleming 2000, & Milne et al. 2005. Credit: Robert A. Rohde.
This figure shows sea level rise since the end of the last glacial episode based on data from Fleming et al. 1998, Fleming 2000, & Milne et al. 2005. Credit: Robert A. Rohde.

Mean sea level (MSL) is a measure of the average height of the ocean's surface (such as the halfway point between the mean high tide and the mean low tide); used as a standard in reckoning land elevation.[25] MSL also plays an extremely important role in aviation, where standard sea level pressure is used as the measurement datum of altitude at flight levels.

The upper figure at right shows the change in annually averaged sea level at 23 geologically stable tide gauge sites with long-term records as selected by Douglas (1997). The thick dark line is a three-year moving average of the instrumental records. This data indicates a sea level rise of ~27.5 cm from 1800-2000. Because of the limited geographic coverage of these records, it is not obvious whether the apparent decadal fluctuations represent true variations in global sea level or merely variations across regions that are not resolved.

For comparison, the recent annually averaged satellite altimetry data [1] from TOPEX/Poseidon are shown in red. These data indicate a somewhat higher rate of increase than tide gauge data, however the source of this discrepancy is not obvious. It may represent systematic error in the satellite record and/or incomplete geographic sampling in the tide gauge record. The month to month scatter on the satellite measurements is roughly the thickness of the plotted red curve.

The second figure at the right shows changes in sea level during the Holocene, the time following the end of the most recent glacial period, based on data from Fleming et al. 1998, Fleming 2000, & Milne et al. 2005. These papers collected data from various reports and adjusted them for subsequent vertical geologic motions, primarily those associated with post-glacial continental and hydroisostatic rebound. The first refers to deformations caused by the weight of continental ice sheets pressing down on the land, the latter refers to uplift in coastal areas resulting from the increased weight of water associated with rising sea levels. It should be noted that because of the latter effect and associated uplift, many islands, especially in the Pacific, exhibited higher local sea levels in the mid Holocene than they do today. Uncertainty about the magnitude of these corrections is the dominant uncertainty in many measurements of Holocene scale sea level change.

The black curve is based on minimizing the sum of squares error weighted distance between this curve and the plotted data. It was constructed by adjusting a number of specified tie points, typically placed every 1 kyr and forced to go to 0 at the modern day. A small number of extreme outliers were dropped. It should be noted that some authors propose the existence of significant short-term fluctuations in sea level such that the sea level curve might oscillate up and down about this ~1 kyr mean state. Others dispute this and argue that sea level change has been a smooth and gradual process for essentially the entire length of the Holocene. Regardless of such putative fluctuations, evidence such as presented by Morhange et al. (2001) suggests that in the last 10 kyr sea level has never been higher than it is at present.

The lower figure shows sea level rise since the end of the last glacial episode based on data from Fleming et al. 1998, Fleming 2000, & Milne et al. 2005.

At least one episode of rapid deglaciation, known as meltwater pulse 1A, is agreed upon and indicated on the plot. A variety of other accelerated periods of deglaciation have been proposed (i.e. MWP-1B, 2, 3, 4), but it is unclear if these actually occurred or merely reflect misinterpretation of difficult measurements. No other events are evident in the data presented above.

The lowest point of sea level during the last glaciation is not well constrained by observations (shown here as a dashed curve), but is generally argued to be approximately 130 +/- 10 m below present sea level and to have occurred at approximately 22 +/- 3 thousand years ago. The time of lowest sea level is more or less equivalent to the last glacial maximum. Prior to this time, ice sheets were still increasing in size so that sea level was decreasing almost continuously over a period of approximately 100,000 years.


Satellite caption is for a composite image of the Mediterranean Sea. Credit: Eric Gaba.
This bathymetric map of the Mediterranean Sea shows the likely surface above sea level during the last ice age in orange-brown. Credit: Jean Mascle & Georges Mascle, Geological and Morpho-Tectonic Map of the Mediterranean Domain, Digital Terrain Model (DTM), at 500m, DTM at 1500m GEBCO Atlas (General Bathymetric Chart of the Oceans), Morpho-bathymetric synthesis of the Mediterranean Sea, CIESM and IFREMER.{{fairuse}}
This Digital Elevation Model (250 m grid) is of the seabed of the Aegean Sea derived from the combination and reprocessing of swath bathymetry, GEBCO and single-beam echo-sounder data in the framework of DG MARE EMODNET Bathymetry project. Credit: Dimitris Sakellariou and Konstantina Tsampouraki-Kraounaki.{{fairuse}}

Def. a large body of salty water is called a sea.

"In terms of geography, a sea is part of the ocean partially enclosed by land. Seas are smaller than oceans and are usually located where the land and ocean meet. Typically, seas are partially enclosed by land."[26]

The image on the right shows those subsurface areas in orange-brown like the other bathymetric maps that was likely above sea level during the last ice age. This is possibly what the Mediterranean looked like to the ancient Egyptians and Greeks.

The image on the left is a 2016 bathymetric map of the Aegean Sea floor. Contours are 250 m each. The reddest is at 250 m, the next two lighter reds or oranges are 500 m and 750 m, and the yellow starts at 1,000 m. This is a close-up view of what is in the image on the right. Compare these with the image from Commons File:Aegean Sea map bathymetry-fr.jpg.


The Bay of San Sebastian is imaged from above. Credit: Hynek Moravec.
The theory of bay formation is described. Credit: Surachit.

Def. a body of water more or less three-quarters surrounded by land is called a bay.


The two fjords in this picture are Barry Arm on the left and College Fiord on the right, in Prince William Sound, Alaska. Credit: Hunter.
Fjord is at Aurland, Norway. Credit: Yorian.

A fjord is usually understood to be a "glacial valley that has been invaded by the sea. A fjord generally has a U-shaped profile with deep water near shore. The two fjords in this picture [on the right] are Barry Arm on the left and College Fiord on the right, in Prince William Sound, Alaska."[27]

Def. a long, narrow, deep inlet between cliffs is called a fjord.


The Persian Gulf is a deep inlet of the sea between Arabia and western Asia. Credit: NASA.

Def. a deep inlet of the sea almost surrounded by land, with a narrow mouth is called a gulf.

Def. a portion of an ocean or sea extending into the land; a partially landlocked sea is called a gulf.


Strait of Gibraltar between Morocco and Spain is seen from STS-59, where north is to the left. Credit: NASA.

Def. a narrow channel of water connecting two larger bodies of water is called a strait.

"The Atlantic Ocean, Straits of Gibraltar, and Alboran Sea (the westernmost portion of the Mediterranean Sea) separate Spain on the [top] from Morocco on the [bottom]. Algeciras Harbor is the prominent notch cut out of the eastern end of the north shore of the Strait; the Rock of Gibraltar is the tiny arrowhead that separates the notch from the Alboran Sea. The Sierra Nevada, farther away down the Spanish coast, lives up to its name in this April scene. The difference in elevation between the Sierra Morena and the Guadalquivir River valley is highlighted nicely by cumulus clouds. Tangier, Morocco can be seen as a light-toned spot on the southern shore of the Strait, near the entrance to the Atlantic Ocean."[28]


The Vivari Channel in Albania links Lake Butrint with the Straits of Corfu. Credit: Roquai.


  1. a natural deeper course through a reef, bar, bay, or any shallow body of water,
  2. a navigable part of a river, or
  3. a narrow body of water between two land masses is called a channel.


The mouth of an estuary is about in the center. Credit: US Environmental Protection Agency.

Def. coastal water body where ocean tides and river water merge or an ocean inlet also fed by fresh river water is called an estuary.


Klöntalersee is a natural lake in the Canton of Glarus, Switzerland. Credit: Ikiwaner.
Lake Billy Chinook is in the Deschutes National Forest, Oregon, USA. Credit: US Department of Agriculture.

Def. a large, landlocked stretch of water is called a lake.

Great Lakes[edit]

This is a Landsat image of Lake Superior in North America. Credit: NASA.

"Of all the world's freshwater lakes, North America's Great Lakes are unique. Their five basins combine to form a single watershed with one common outlet to the ocean. The total volume of the lakes is about 5,475 cubic miles, more than 6,000 trillion gallons."[29]

"The Huron Lobe and the Michigan Lobe are at the same elevation and are connected by the 120-foot-deep Mackinac Strait, also at the same elevation. Lakes are separated from each other by streams and rivers. The Strait of Mackinac is not a river. It is 3.6 to 5 miles wide, wider than most lakes are long. In essence, it is just a narrowing, not a separation of the two lobes of Lake Michigan-Huron."[29]

"The flow between the two lakes can reverse. Because of the large connecting channel, the two can equalize rapidly whenever a water level imbalance occurs. Gauge records for the lakes clearly show them to have identical water level regimes and mean long-term behavior; that is, they are hydrologically considered to be one lake."[29]

"The Great Lakes are Superior, with an area of 31,820 square miles (82,414 km) shared by the United States and Canada; Huron, with an area of 23,010 square miles (59,596 sq. km) shared by the United States and Canada; Michigan, with an area of 22,400 square miles (58,016 sq. km) entirely in the United States; Erie, with an area of 9,930 square miles (25,719 km) shared by the United States and Canada; and Ontario, with an area of 7,520 square miles (19,477 km) shared by the United States and Canada."[29]

Kettle lakes[edit]

These kettles are freshly formed in the outwash plain of the retreating Bering Glacier in southern Alaska. Credit: Hunter.
This kettle lake is in the highlands of Isunngua, Greenland. Credit: Amy Tikkanen.

The lakes in the image on the right "are freshly formed in the outwash plain of the retreating Bering Glacier in southern Alaska."[27]

In the image on the left is a kettle lake in the highlands of Isunngua, Greenland.

Dead ice lakes[edit]

Lakes in dead ice landscape are part of the 1890 Brúarjökull end moraine complex. Credit: Ólafur Ingólfsson.

"Lake sediments constitute the only continuous archives in the area that can register both local and regional environmental changes, including tephra fall-outs. The area is abundant in lakes and the strategy is to core at least three different lakes of varying settings: (i) one should be connected, through influence of glacial melt water, with the present day glacier as well as with the large surge events, which means that it should be a major sedimentation basin within the main extraglacial fluvial system [such lakes as in the image on the right may occur in a dead ice zone from downwasting], (ii) one lake should only be connected to a glacial melt water system during surges, and (iii) one basin should be without direct contact to the glacial system, but register the regional environmental and climate changes, including local and regional tephras."[30]

Thermokarst lakes[edit]

An aerial view shows thermokarst lakes in northeast Siberia. Credit: Dmitry Solovyov/REUTERS.

Def. "water that forms transition layers at mineral/water and mineral/water/ice interfaces in frozen ground"[31] is called interfacial water.

Def. "water occurring in unfrozen zones (taliks and cryopegs) within permafrost"[31] is called interpermafrost water.

At the right is an "aerial view [of] thermokarst lakes outside the town of Chersky in northeast Siberia [on] August 28, 2007."[32]

Def. "a lake occupying a closed depression formed by settlement of the ground following thawing of ice-rich permafrost or the melting of massive ice"[31] is called a thermokarst lake.

"Paul Lake is located [...] at the border of Wisconsin and the upper peninsula of Michigan, USA [...] The center of the property is positioned at 46°13'N 89°32'E, with an altitude range between 500 and 520 m."[33]

It "lies in [the] Northern Highland Province, which is the southernmost extension of the Canadian Shield. This province is characterized primarily by Pre-Cambrian bedrocks capped by a thin layer of sedimentary rocks left by the Paleozoic seas. On top of this formation are glacial deposits left by the Woodfordian and Valderan substages of the Wisconsinian glaciers. These glacial deposits are young and the drainage system is poorly developed. The surface deposits are characteristic of glacial retreat, consisting of infertile, sandy, pitted glacial out-wash or boulder and clay morainic deposits. As a result of their composition, the soils have a reduced capacity for cation exchange, leaving them very susceptible to acidification. Many of the lakes in this region are kettle lakes, others originate from irregular depressions in the ground moraine or were scoured out of the bedrock as the glaciers passed."[33]

"Paul Lake has a surface area of 1 ha, a mean depth of 6 m, and a maximum depth of 13 m [...]. All the water entering Paul Lake comes from atmospheric deposition and groundwater seepage. Paul Lake generally remains stratified year-long because of a biogenic meromixis [...] and has been classified mesotrophic [...]. The concentration of soluble reactive phosphorus remains low in surface waters year-long, but nutrient regeneration at the oxic/anoxic transition promotes phyto-planktonic blooms just above this interface [...]."[33]

Ribbon lakes[edit]

The two largest lakes, Seneca and Cayuga, are so deep that the base of their lakebeds are below sea level. Credit: NASA/JSC.
The Kawartha Lakes in central Ontario, Canada, are labeled. Credit: NASA.
A Polish ribbon lake has variable width and an interruption between segments of the course. Credit: NASA.

"A late fall snowstorm frosted the hills of the Finger Lakes region of central New York in early December. Shapes of the snow-covered hills are accented by the low Sun angles, and contrast with the darker, finger-shaped lakes filling the region’s valleys. The steep, roughly parallel valleys and hills of the Finger Lakes region were shaped by advancing and retreating ice sheets that were as much as 2 miles deep during the last ice age (2 million years to about 10,000 years ago). River valleys were scoured into deep troughs; many are now filled with lakes. The two largest lakes, Seneca and Cayuga, are so deep that the base of their lakebeds are below sea level."[34]

"The cities of Rochester, Syracuse, and Ithaca are included in this field-of-view, taken from the International Space Station. These three cities enjoy large seasonal snowpacks, thanks to the influence of the Great Lakes producing lake-effect snowstorms. Despite its reputation for long winters, the region is balmy compared with the glacial climate present when the landscape was carved. At the time of the greatest ice extent, yearly average temperatures over northern North America were several degrees lower than today."[34]


Black pond in located near Esher, Surrey, UK. Credit: Freedom to share.

Def. a natural inland body of standing water that is smaller than a lake is called a pond.

Intermittent lakes[edit]

Def. a lake that is intermittent; that is, a lake that is dry for part of the year is called an intermittent lake.


A freshwater swamp forest is in Florida. Credit: USGS.
Swamp is at peat mining near Rudzensk, Belarus. Credit: Alex Zelenko.

Def. land that is covered mostly with water, with occasional marshy and soggy areas is called a wetland.

Def. a type of wetland that stretches for vast distances is called a swamp.


Aerial view, extreme long shot, looks down as the Limpopo River winds its way through Southern Mozambique. Credit: TSGT Cary Humphries.
Loboc River is in the Bohol province of the Philippines. Credit: Qaalvin.

Def. a large and often winding stream which drains a land mass, carrying water down from higher areas to a lower point, ending at an ocean or in an inland sea is called a river.


This is an aerial photo of the meanders by the Río Cauto in Cuba. Credit: Not home.

Def. a winding, crooked, or involved course or a tortuous or intricate movement of water as a stream or river is called a meander.


Rapids are before the Rhine Falls. Credit: Gulliveig.

Def. a rough section of a river or stream which is difficult to navigate due to the swift and turbulent motion of the water is called a rapid.

On the right are rapids featuring white water before the Rhine Falls.


Goðafoss is in Iceland. Credit: Roger McLassus.
Salto Angel is in Canaima, Venezuela. Credit: Poco a poco.

Def. a flow of water over the edge of a cliff is called a waterfall.

Angel Falls in the image on the left is the world's tallest at 979 m.


Def. the end of a river out of which water flows into a sea or other large body of water is called the mouth.


Def. an underwater vortex similar to a whirlwind that is capable of dislodging, picking up, and moving boulders is called a kolk.


  1. Underneath ice there may be water.

See also[edit]


  1. NCEI (formerly NGDC) (2006). Atlantic bathymetry. Washington, DC USA: NCEI (formerly NGDC), NESDIS, NOAA. Retrieved 2018-01-24.
  2. Norwegian Sea, Great Soviet Encyclopedia (in Russian)
  3. Norwegian Sea, Encyclopædia Britannica on-line
  4. ICES, 2007, p. 1
  5. Westerly storms warm Norway. The Research Council of Norway. Forskningsradet.no (3 September 2012). Retrieved on 2013-03-21.
  6. "Limits of Oceans and Seas, 3rd edition" (PDF). International Hydrographic Organization. 1953. Retrieved 6 February 2010.
  7. 7.0 7.1 7.2 7.3 Terje Thornes & Oddvar Longva "The origin of the coastal zone" in: Sætre, 2007, pp. 35–43
  8. Roald Sætre Driving forces in: Sætre, 2007, pp. 44–58
  9. 9.0 9.1 Blindheim, 1989, pp. 366–382
  10. 10.0 10.1 10.2 10.3 10.4 Laura Spinney (December 2012). "Searching for Doggerland". National Geographic Magazine: 6. http://waughfamily.ca/Ancient/Doggerland%20-%20National%20Geographic.pdf. Retrieved 2017-02-02. 
  11. Clive Waddington (December 2012). "Searching for Doggerland". National Geographic Magazine: 6. http://waughfamily.ca/Ancient/Doggerland%20-%20National%20Geographic.pdf. Retrieved 2017-02-02. 
  12. C.Michael Hogan. 2011. Celtic Sea. eds. P.saundry & C.Cleveland. Encyclopedia of Earth. National Council for Science and the /environment. Washington DC.
  13. 13.0 13.1 13.2 13.3 Haslam, D. W. (Hydrographer of the Royal Navy) (29 March 1976). "It's the Celtic Sea—official, In: The Times". p. 15. Missing or empty |url= (help)
  14. Danois, Edouard Le (1957). Marine Life of Coastal Waters: Western Europe. Harrap. p. 12.
  15. Cooper, L. H. N. (2 February 1972). "In Celtic waters, In: The Times". p. 20. Missing or empty |url= (help)
  16. The Atlas of Great Britain and Northern Ireland. Clarendon Press. 1963. pp. 20–21.; cited in
    Shergold, Vernon G. (27 January 1972). "Celtic Sea: a good name, In: The Times". p. 20. Missing or empty |url= (help)
  17. Vielvoye, Roger (24 January 1972). "Industry in the regions Striking oil in Wales and West Country, In: The Times". p. 19. Missing or empty |url= (help)
  18. "Celtic Sea". 16 December 1974.
  19. "Limits of Oceans and Seas, 3rd edition + corrections" (PDF). International Hydrographic Organization. 1971. p. 42 [corrections to page 13]. Retrieved 6 February 2010.
  20. Hardisty, Jack (1990). The British Seas: an introduction to the oceanography and resources of the north-west European continental shelf. Taylor & Francis. pp. 20–21. ISBN 0-415-03586-4.
  21. 21.0 21.1 Carolina Matos (28 August 2013). "Pico: New archaeological evidence reveals human presence before Portuguese occupation – Azores". Portuguese American Journal 2013 (8). http://portuguese-american-journal.com/pico-new-archeological-evidence-reveals-human-presence-before-portuguese-occupation-azores/. Retrieved 2017-04-27. 
  22. 22.0 22.1 Paul van den Bogaard (2013). "The origin of the Canary Island Seamount Province - New ages of old seamounts". Scientific Reports 3: 2107. doi:10.1038/srep02107. https://www.nature.com/articles/srep02107. Retrieved 2017-04-27. 
  23. Nadia Mhammdi, Maria Snoussi, Fida Medina, and El Bachir Jaaïdi (2014). "Recent sedimentation in the NW African shelf". Geological Society, London, Memoirs 41: 131-146. doi:10.1144/M41.10. https://www.researchgate.net/profile/Nadia_Mhammdi/publication/283944649_Mhammdietal2014GSL/links/564a459a08ae9cd9c826b186.pdf. Retrieved 2017-04-27. 
  24. 24.0 24.1 24.2 Dornier and Alenia Spazio (31 July 2013). Weddell Sea/ScanSAR. Pasadena, California USA: NASA/JPL. Retrieved 2014-12-16.
  25. What is "Mean Sea Level"?. Proudman Oceanographic Laboratory.
  26. National Ocean Service (March 25, 2014). What's the difference between an ocean and a sea?. N/MB6, SSMC4, Room 9149, 1305 East-West Hwy, Silver Spring, MD 20910 USA: NOAA's National Ocean Service. Retrieved 2014-12-18.
  27. 27.0 27.1 Hunter (2014). Glaciers. New York, USA: CUNY. Retrieved 2014-11-24.
  28. Maura White (14 April 1994). Morocco and border of spain as seen from STS-59. Houston, Texas USA: Johnson Space Center. Retrieved 2014-12-18.
  29. 29.0 29.1 29.2 29.3 Pearson Education, Inc. (2014). Michigan and Huron: One Lake or Two?. InfoPlease.com. Retrieved 2014-12-21.
  30. Kurt Kjær and Ólafur Ingólfsson (2004). The Brúarjökull Project: Sedimentary environments of a surging glacier. Iceland: Brúarjökull Project. Retrieved 2014-11-26.
  31. 31.0 31.1 31.2 Jane Beitler (19 September 2014). Cryosphere Glossary. National Snow and Ice Data Center. Retrieved 2014-09-17.
  32. Dmitry Solovyov (28 August 2007). Large increase in leakage of methane gas from the Arctic seabed. The We at WePlanet. Retrieved 2014-09-20.
  33. 33.0 33.1 33.2 Charles-Philippe Lienemann, Martial Taillepert, Didier Perret, and Jean-François Gaillard (1997). "Association of cobalt and manganese in aquatic systems: Chemical and microscopic evidence". Geochimica et Cosmochimica Acta 61 (7): 1437-46. http://shadow.eas.gatech.edu/~mtaillef/Research/GCA1997.pdf. Retrieved 2014-10-23. 
  34. 34.0 34.1 Charles Ichoku (20 December 2004). New York's Finger Lakes. Washington, DC USA: NASA. Retrieved 2014-12-19.

External links[edit]