Sea-level curve

The sea-level curve is the representation of the changes of the sea level throughout the geological history.

The first such curve is the Vail curve or Exxon curve. The names of the curve refer to the fact that in 1977 a team of Exxon geologists from Esso Production Research headed by Peter Vail published a monograph on global eustatic sea-level changes. Their sea-level curve was based on seismic and biostratigraphic data accumulated during petroleum exploration.[1]

The Vail curve (and the monograph itself) was the subject of debate among geologists, because it was based on undisclosed commercially confidential stratigraphic data, and hence not independently verifiable.[2] Because of this, there were later efforts to establish a sea-level curve based on non-commercial data.

In 1987–1988 a revised eustatic sea-level curve for the Mesozoic and Cenozoic eras was published, now known as the Haq sea-level curve, in reference to the Pakistani-American Oceanographer Bilal Haq.[1]

Phanerozoic Sea Level
Comparison of two sea level reconstructions during the last 500 Myr: Exxon curve and Hallam curve. The scale of change during the last glacial/interglacial transition is indicated with a black bar.

References

  1. ^ a b Principles of Paleoclimatology, by Thomas M. Cronin (1999) ISBN 0-231-10955-5, pp. 381, 382
  2. ^ "Climate Change", William James Burroughs p 87

See also

Bahama Banks

The Bahama Banks are the submerged carbonate platforms that make up much of the Bahama Archipelago. The term is usually applied in referring to either the Great Bahama Bank around Andros Island, or the Little Bahama Bank of Grand Bahama Island and Great Abaco, which are the largest of the platforms, and the Cay Sal Bank north of Cuba. The islands of these banks are politically part of the Bahamas. Other banks are the three banks of the Turks and Caicos Islands, namely the Caicos Bank of the Caicos Islands, the bank of the Turks Islands, and wholly submerged Mouchoir Bank. Further southeast are the equally wholly submerged Silver Bank and Navidad Bank north of the Dominican Republic.

Carbonate platform

A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually microbes) which induce carbonate precipitation through their metabolism. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others: light, water temperature, transparency and pH-Value. For example, carbonate sedimentation along the Atlantic South American coasts takes place everywhere but at the mouth of the Amazon River, because of the intense turbidity of the water there. Spectacular examples of present-day carbonate platforms are the Bahama Banks under which the platform is roughly 8 km thick, the Yucatan Peninsula which is up to 2 km thick, the Florida platform, the platform on which the Great Barrier Reef is growing, and the Maldive atolls. All these carbonate platforms and their associated reefs are confined to tropical latitudes. Today's reefs are built mainly by scleractinian corals, but in the distant past other organisms, like archaeocyatha (during the Cambrian) or extinct cnidaria (tabulata and rugosa) were important reef builders.

List of submarine volcanoes

A list of active and extinct submarine volcanoes and seamounts located under the world's oceans. There are estimated to be 40,000 to 55,000 seamounts in the global oceans. Almost all are not well-mapped and many may not have been identified at all. Most are unnamed and unexplored. This list is therefore confined to seamounts that are notable enough to have been named and/or explored.

Mastogloia Sea

The Mastogloia Sea is one of the prehistoric stages of the Baltic Sea in its development after the last ice age. This took place ca. 8000 years ago following the Ancylus Lake stage and preceding the Littorina Sea stage.

Note: The dates used in this article are expressed in radiocarbon years before present (‘present’ in the radiocarbon context meaning, for historical reasons, the year 1950 AD). Expressed in calendar years before present, all dates would be several hundred years older.

Oceanic plateau

An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.There are 184 oceanic plateaus covering an area of 18,486,600 km2 (7,137,700 sq mi), or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map).

Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges.

Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the United States.

In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources.

These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As a consequence, they tend to "dock" to continental margins and be preserved as accreted terranes. Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had a dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean.

Outline of oceanography

The following outline is provided as an overview of and introduction to Oceanography.

Physical impacts of climate change

This article is about the physical impacts of climate change; the change referred to may be due to natural causes but in the political context is more likely to be that due to the result of human activity, global warming. For some of these physical impacts, their effect on social and economic systems are also described.

This article refers to reports produced by the IPCC. In their usage, "climate change" refers to a change in the state of the climate that can be identified by changes in the mean and/or variability of its properties, and that persists for extended periods, typically decades or longer (IPCC, 2007d:30).

Physical oceanography

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Physical oceanography is one of several sub-domains into which oceanography is divided. Others include biological, chemical and geological oceanography.

Physical oceanography may be subdivided into descriptive and dynamical physical oceanography.Descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precisely as possible.

Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and numerical models. These are part of the large field of Geophysical Fluid Dynamics (GFD) that is shared together with meteorology. GFD is a sub field of Fluid dynamics describing flows occurring on spatial and temporal scales that are greatly influenced by the Coriolis force.

Polystrate fossil

A polystrate fossil is a fossil of a single organism (such as a tree trunk) that extends through more than one geological stratum. This term is typically applied to "fossil forests" of upright fossil tree trunks and stumps that have been found worldwide, i.e. in the Eastern United States, Eastern Canada, England, France, Germany, and Australia, typically associated with coal-bearing strata. Within Carboniferous coal-bearing strata, it is also very common to find what are called Stigmaria (root stocks) within the same stratum. Stigmaria are completely absent in post-Carboniferous strata, which contain either coal, polystrate trees, or both. The word polystrate is not a standard geological term. This term is typically found in creationist publications.

Raised beach

A raised beach, coastal terrace, or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin, mostly an old abrasion platform which has been lifted out of the sphere of wave activity (sometimes called "tread"). Thus, it lies above or under the current sea level, depending on the time of its formation. It is bounded by a steeper ascending slope on the landward side and a steeper descending slope on the seaward side (sometimes called "riser"). Due to its generally flat shape it is often used for anthropogenic structures such as settlements and infrastructure.A raised beach is an emergent coastal landform. Raised beaches and marine terraces are beaches or wave-cut platforms raised above the shoreline by a relative fall in the sea level.Around the world, a combination of tectonic coastal uplift and Quaternary sea-level fluctuations has resulted in the formation of marine terrace sequences, most of which were formed during separate interglacial highstands that can be correlated to marine isotope stages (MIS).A marine terrace commonly retains a shoreline angle or inner edge, the slope inflection between the marine abrasion platform and the associated paleo sea-cliff. The shoreline angle represents the maximum shoreline of a transgression and therefore a paleo-sea level.

San Matías Gulf

The San Matias Gulf is an inlet of the Atlantic Ocean off the coast of Patagonia, Argentina. It is bordered by the Río Negro Province to the north and west, and the Valdes Peninsula of the Chubut Province to the south. It is "one of the largest gulfs in the Patagonia region". The gulf is surrounded by plateaus and depressions below sea level similar to the gulf itself but that are not flooded by the sea at present.The gulf was the subject of scientific investigation for its unusually large sand waves and their movement.The local fishing industry may be unsustainably harvesting the purple clam (Amiantis purpurata), the Tehuelche scallop (Aequipecten tehuelchus), the blue mussel (Mytilus edulis), and the ribbed mussel (Aulacomya atra), as well as the Patagonian octopus (Octopus tehuelchus). The 2003 commercial squid harvest broke the previous record set in 2001 by more than double at 5,535 tonnes (5,448 long tons; 6,101 short tons). As of 2014, this gulf is the only location in the world where swimming with whales is permitted for tourism, with right whales.The San Matías Gulf has a history of tectonic origin. Prior to the deglaciation that followed the last glacial period San Matías Gulf was a dry flatland below sea level. As global deglaciation went on after the Last Glacial Maximum sea level rose so that 11,000 years before present sea level surpassed the San Matías sill flooding the whole basin. This sill is currently 60 meters below sea level. The gulf has been repeatedly dried up and flooded during Quaternary glacial and interglacial periods respectively.

Sequence stratigraphy

Sequence stratigraphy is a branch of geology that attempts to subdivide and link sedimentary deposits into unconformity bound units on a variety of scales and explain these stratigraphic units in terms of variations in sediment supply and variations in the rate of change in accommodation space (relative sea level, the combination of eustatic sea level and tectonic subsidence). The essence of the method is mapping of strata based on identification of surfaces which are assumed to represent time lines (e.g. subaerial unconformities, maximum flooding surfaces), and therefore placing stratigraphy in chronostratigraphic framework. Sequence stratigraphy is a useful alternative to a lithostratigraphic approach, which emphasizes similarity of the lithology of rock units rather than time significance.

Sequence stratigraphy deals with genetically related sedimentary strata bounded by unconformities.

The "sequence" part of the name refers to cyclic sedimentary deposits. Stratigraphy is the geologic knowledge about the processes by which sedimentary deposits form and how those deposits change through time and space on the Earth's surface.

Settlement of the Americas

The most recent settlement of the Americas began when Paleolithic hunter-gatherers entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum.

These populations expanded south of the Laurentide Ice Sheet and rapidly throughout both North and South America, by 14,000 years ago. The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians.

The peopling of the Americas is a long-standing open question, and while advances in archaeology, Pleistocene geology, physical anthropology, and DNA analysis have shed progressively more light on the subject, significant questions remain unresolved. While there is general agreement that the Americas were first settled from Asia, the pattern of migration, its timing, and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear.The prevalent migration models outline different time frames for the Asian migration from the Bering Straits and subsequent dispersal of the founding population throughout the continent. Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.The "Clovis first theory" refers to the 1950s hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated since 2000, pushing back the possible date of the first peopling of the Americas to about 13,200–15,500 years ago.

Stratigraphy

Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.

Stratigraphy has two related subfields: lithostratigraphy (lithologic stratigraphy) and biostratigraphy (biologic stratigraphy).

Tollmann's bolide hypothesis

Tollmann's bolide hypothesis is a hypothesis presented by Austrian paleontologist Edith Kristan-Tollmann and geologist Alexander Tollmann in 1994. The hypothesis postulates that one or several bolides (asteroids or comets) struck the Earth around 7640 ± 200 years BCE, with a much smaller one approximately 3150 ± 200 BCE. The hypothesis tries to explain early Holocene extinctions and possibly legends of the Universal Deluge.The claimed evidence for the event includes stratigraphic studies of tektites, dendrochronology, and ice cores (from Camp Century, Greenland) containing hydrochloric acid and sulfuric acid (indicating an energetic ocean strike) as well as nitric acids (caused by extreme heating of air).

Christopher Knight and Robert Lomas in their book, Uriel's Machine, argue that the 7640 BCE evidence is consistent with the dates of formation of a number of extant salt flats and lakes in dry areas of North America and Asia. They argue that these lakes are the remains of multiple-kilometer-high waves that penetrated deeply into continents as the result of oceanic strikes that they proposed occurred. Research by Quaternary geologists, palynologists and others has been unable to confirm the validity of the hypothesis and proposes more frequently occurring geological processes for some of the data used for the hypothesis. Dating of ice cores and Australasian tektites has shown long time span differences between the proposed impact times and the impact ejecta products.

Undersea mountain range

Undersea mountain ranges are mountain ranges that are mostly or entirely underwater, and specifically under the surface of an ocean. If originated from current tectonic forces, they are often referred to as a mid-ocean ridge. In contrast, if formed by past above-water volcanism, they are known as a seamount chain. The largest and best known undersea mountain range is a mid-ocean ridge, the Mid-Atlantic Ridge. It has been observed that, "similar to those on land, the undersea mountain ranges are the loci of frequent volcanic and earthquake activity".

Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

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