1.
Agulhas Passage
–
The Agulhas Passage is an abyssal channel located south of South Africa between the Agulhas Bank and Agulhas Plateau. Between the Agulhas Bank and the Agulhas Passage the boundary between the Earths crust and the mantle ascend from 25 to 14 km over 50 km which is normal for a continent-ocean boundary. The crustal thickness under the Agulhas Passage varies from 6 to 10 km which is normal for oceanic crust. The sedimentary layers are thin in the western Agulhas Passage. In the central parts of the passage, in contrast, they can reach 1,300 m, the southern part is affected by thinning and erosion. In the Indian Ocean, the Agulhas Current is dissipated into a gyre which finally brings parts of the masses back to the Natal Valley. North Atlantic Deep Water flows north through the Agulhas Passage and then west of the Mozambique Ridge and through the Transkei Basin east of the ridge and then into the Indian Ocean. South of South Africa NADW is found close to a depth of 2,500 m where it transports 2.9 Sverdrups at a speed of 4 cm/s, antarctic Intermediate Water flows from Antarctica into the Indian Ocean from where it reaches Africa from the east. It flows south through the Agulhas Passage and then follows the Agulhas Current and retroflects back into the Indian Ocean
Agulhas Passage
–
The Agulhas Passage is located between the Agulhas Bank and the Agulhas Plateau
2.
Agulhas Basin
–
The Agulhas Basin is an oceanic basin located south of South Africa where the South Atlantic Ocean and south-western Indian Ocean meet. Part of the African Plate, it is bounded by the Agulhas Ridge to the north and the Southwest Indian Ridge to the south, by the Meteor Rise to the west, a large number of bathymetric anomalies hints at the basins dynamic tectonic history. In a Late Paleocene reconstruction of the opening of the South Atlantic Ocean the Meteor Rise lies conjugate to the Islas Orcadas Rise, the separation of the Meteor Rise and the Islas Orcadas Rise marks the beginning of the formation of the Agulhas Basin. The Agulhas Ridge extends from the tip of the Meteor Rise towards the Agulhas Bank south of South Africa. The ridge, however, ends abruptly in a plateau at 40°S 15°E where it intersects a northeastward-trending spreading centre that was abandoned during the Early Paleocene. The presence of a tectonic plate between these structures was first proposed by LaBrecque & Hayes 1979. They named it the Malvinas Plate and proposed that it was active from 90 Ma until the spreading ceased in the Agulhas Basin at 65 Ma, the plate is located at a proto-Bouvet Triple Junction. Furthermore, magnetic anomalies on the Malvinas Plate do not align with their conjugates on the African Plate if the spreading rates and directions of South America and Africa are used as a guide. They also noted that the Agulhas Fracture Zone do not lay perpendicular to traces of the South America-Africa spreading north of it and cannot, the Agulhas Rift is the abandoned Malvinas-Africa ridge crest. 97 Ma the plate boundary in the Agulhas Basin was reorganised when the Mid-Atlantic Ridge made an eastward jump and this brought the boundary towards the Agulhas Plateau where excessive volcanism was building a large igneous province. The inception of the Malvinas Plate accompanied this shortening of the Agulas Fracture Zone,61 Ma, the Malvinas Plate was finally incorporated into the African Plate when the Malvinas-Africa ridge was abandoned as the result of a westward ridge jump along the Agulhas-Falkland Fracture Zone. This second ridge jump reduced one of the most spectacular fracture zones in Earths history —1,200 km in length — to 180 km, the Agulhas Current flows south along the African east coast. When it reaches the tip of Africa, it retroflects back into the Indian Ocean. At this retroflection it leakes warm core eddies known as Agulhas rings into the South Atlantic, in the Agulhas basin, half of these rings are subdivided one or several times. Antarctic Bottom Water originated in the Oligocene with the opening of the Drake Passage, AABW mixes with other masses in the Antarctic Circumpolar Current to form the Circumpolar Deep Water. In the Agulhas Basin CDW flows northward and is deflect mostly westward by the Agulhas Ridge. A branch of CDW, however, enters the Cape Basin west of the ridge from where it flows west along the side of the ridge before being deflected north-east at the eastern end of the ridge. This long detour in the Cape Basin and mixing with North Atlantic Deep Water results in water than other CDW masses
Agulhas Basin
–
The Agulhas Basin and some of the bathymetric structures mentioned in the text
3.
Geographic coordinate system
–
A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection. The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead. Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before 1300, in 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the equator, the north pole is 90° N, the south pole is 90° S. The 0° parallel of latitude is designated the equator, the plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E, the combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The grid formed by lines of latitude and longitude is known as a graticule, the origin/zero point of this system is located in the Gulf of Guinea about 625 km south of Tema, Ghana. To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0. 3% larger than the radius measured through the poles, the shorter axis approximately coincides with the axis of rotation
Geographic coordinate system
–
Longitude lines are perpendicular and latitude lines are parallel to the equator.
4.
South Africa
–
South Africa, officially the Republic of South Africa, is the southernmost country in Africa. South Africa is the 25th-largest country in the world by land area and it is the southernmost country on the mainland of the Old World or the Eastern Hemisphere. About 80 percent of South Africans are of Sub-Saharan African ancestry, divided among a variety of ethnic groups speaking different Bantu languages, the remaining population consists of Africas largest communities of European, Asian, and multiracial ancestry. South Africa is a multiethnic society encompassing a variety of cultures, languages. Its pluralistic makeup is reflected in the recognition of 11 official languages. The country is one of the few in Africa never to have had a coup détat, however, the vast majority of black South Africans were not enfranchised until 1994. During the 20th century, the black majority sought to recover its rights from the dominant white minority, with this struggle playing a role in the countrys recent history. The National Party imposed apartheid in 1948, institutionalising previous racial segregation, since 1994, all ethnic and linguistic groups have held political representation in the countrys democracy, which comprises a parliamentary republic and nine provinces. South Africa is often referred to as the Rainbow Nation to describe the multicultural diversity. The World Bank classifies South Africa as an economy. Its economy is the second-largest in Africa, and the 34th-largest in the world, in terms of purchasing power parity, South Africa has the seventh-highest per capita income in Africa. However, poverty and inequality remain widespread, with about a quarter of the population unemployed, nevertheless, South Africa has been identified as a middle power in international affairs, and maintains significant regional influence. The name South Africa is derived from the geographic location at the southern tip of Africa. Upon formation the country was named the Union of South Africa in English, since 1961 the long form name in English has been the Republic of South Africa. In Dutch the country was named Republiek van Zuid-Afrika, replaced in 1983 by the Afrikaans Republiek van Suid-Afrika, since 1994 the Republic has had an official name in each of its 11 official languages. Mzansi, derived from the Xhosa noun umzantsi meaning south, is a name for South Africa. South Africa contains some of the oldest archaeological and human fossil sites in the world, extensive fossil remains have been recovered from a series of caves in Gauteng Province. The area is a UNESCO World Heritage site and has termed the Cradle of Humankind
South Africa
–
Mapungubwe Hill, the site of the former capital of the
Kingdom of Mapungubwe
South Africa
–
Flag
South Africa
–
Arrival of
Jan van Riebeeck, the first European to settle in South Africa, with
Devil's Peak in the background
South Africa
–
Depiction of a
Zulu attack on a Boer camp in February 1838
5.
International waters
–
International waters have no sovereignty, ergo is Terra nullius as no state controls it. All states have the freedom of, fishing, navigation, overflight, laying cables and pipelines, oceans, seas, and waters outside of national jurisdiction are also referred to as the high seas or, in Latin, mare liberum. International waters can be contrasted with internal waters, territorial waters, several international treaties have established freedom of navigation on semi-enclosed seas. The Copenhagen Convention of 1857 opened access to the Baltic by abolishing the Sound Dues and making the Danish Straits an international waterway free to all commercial, several conventions have opened the Bosphorus and Dardanelles to shipping. The latest, the Montreux Convention Regarding the Regime of the Turkish Straits, Other international treaties have opened up rivers, which are not traditionally international waterways. The Danube River is a waterway so that landlocked Austria, Hungary, Moldova, Serbia. The Southern Ocean, Australia claims an economic zone around its Antarctic territorial claim. Since this claim is recognised by four other countries, the EEZ claim is also disputed. Area around Okinotorishima, Japan claim Okinotorishima is an islet and thus they should have an EEZ around it, South China Sea, See Territorial disputes in the South China Sea. Some countries consider the South China Sea as international waters, in addition to formal disputes, the government of Somalia exercises little control de facto over Somali territorial waters. Consequently, much piracy, illegal dumping of waste and fishing without permit has occurred, although water is often seen as a source of conflict, recent research suggests that water management can be a source for cooperation between countries. Such cooperation will benefit participating countries by being the catalyst for larger socio-economic development, the Yearbook of International Cooperation on Environment and Development profiles agreements regarding the Marine Environment, Marine Living Resources and Freshwater Resources. 1972 London Convention on the Prevention of Marine Pollution by Dumping of Wastes,1973 London International Convention for the Prevention of Pollution from Ships,1973 MARPOL1982 United Nations Convention on Law of the Sea. 1997 United Nations Convention on the Law of Non-Navigational Uses of International Watercourses - not ratified, transboundary Groundwater Treaty, Bellagio Draft - proposed, but not signed. Other global conventions and treaties with implications for International Waters,1971 Ramsar Convention on Wetlands
International waters
–
Komárno in
Slovakia is an
inland port on the
Danube River which is an important international
waterway.
International waters
–
Areas outside of exclusive economic zones in dark blue.
International waters
–
Atlantic Ocean - the main zone of sea transport in 15th-20th centuries.
6.
Large igneous province
–
The source of many or all LIPs is variously attributed to mantle plumes or to processes associated with plate tectonics. Types of LIPs can include large volcanic provinces, created through flood basalt, rampino and Stothers cite eleven distinct flood-basalt episodes - occurring in the past 250 million years - which created volcanic provinces and plateaus and coincided with mass extinctions. However, more flood basalts have been recognized, such as the large Ontong Java Plateau, mafic, basalt sea floors and other geological products of normal plate tectonics were not included in the definition. The definition of LIP has been expanded and refined, and is still a work in progress, LIP is now frequently also used to describe voluminous areas of, not just mafic, but all types of igneous rocks. Sub-categorization of LIPs into large volcanic provinces and large plutonic provinces, Large igneous provinces are created during short-lived igneous events resulting in relatively rapid and high-volume accumulations of volcanic and intrusive igneous rock. These events warrant study because, The study of LIPs has economic implications, some workers associate them with trapped hydrocarbons. They are associated with economic concentrations of copper–nickel and iron and they are also associated with formation of major mineral provinces including Platinum-Group Element Deposits, and in the Silicic LIPs, silver and gold deposits. Titanium and vanadium deposits are found in association with LIPs. Future LIP events may pose a hazard to human civilization, LIPs in the geological record have marked major changes in the hydrosphere and atmosphere, leading to major climate shifts and maybe mass extinctions of species. Plate tectonic theory explains topography using interactions between the plates, as influenced by viscous stresses created by flow within the underlying mantle. Since the mantle is extremely viscous, the flow rate varies in pulses which are reflected in the lithosphere by small amplitude. Understanding how the interaction between mantle flow and lithosphere elevation influences formation of LIPs is important to gaining insights into past mantle dynamics, LIPs have played a major role in continental breakup, continental formation, new crustal additions from the upper mantle, and supercontinent cycles. Earth has a shell made of a number of discrete. The mantles flow is driven by the descent of cold tectonic plates during subduction, the surface of the Earth reflects stretching, thickening and bending of the tectonic plates as they interact. In this model, tectonic plates diverge at mid-ocean ridges, where hot mantle rock flows upward to fill the space, plate-tectonic processes account for the vast majority of Earths volcanism. Beyond the effects of convectively driven motion, deep processes have other influences on the surface topography, the convective circulation drives up-wellings and down-wellings in Earths mantle that are reflected in local surface levels. Hot mantle materials rising up in a plume can spread out radially beneath the tectonic plate causing regions of uplift and these ascending plumes play an important role in LIP formation. When created, LIPs often have an extent of a few million km²
Large igneous province
–
Only a few of the largest large igneous provinces are indicated (by the dark purple areas) on this geological map, which depicts crustal geologic provinces as seen in
seismic refraction data.
Large igneous province
–
Three Devil's grade in
Moses Coulee, Washington is part of the
Columbia River Basalt Group LIP.
Large igneous province
–
Illustration showing a vertical
dike and a horizontal sill.
7.
Hotspot (geology)
–
In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. They may be on, near to, or far from plate boundaries. Currently, there are two hypotheses that attempt to explain their origins, one suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths and this hypothesis considers the term hotspot to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well known examples include Hawaii, Iceland and Yellowstone and it was later postulated that hotspots are fed by narrow streams of hot mantle rising from the Earths core–mantle boundary in a structure called a mantle plume. Whether or not such mantle plumes exist is currently the subject of a controversy in Earth science. Estimates for the number of hotspots postulated to be fed by mantle plumes has ranged from about 20 to several thousands, over the years, Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the currently most active volcanic regions to which the hypothesis is applied. As a result, they are less explosive than subduction zone volcanoes, where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites. These rhyolites can form violent eruptions, for example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures, the hotspot hypothesis is now closely linked to the mantle plume hypothesis. Hotspot volcanoes are considered to have a different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries, when one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the plate. It is this that fuels a chain of volcanoes, such as the Aleutian Islands, the joint mantle plume/hotspot hypothesis envisages the feeder structures to be fixed relative to one another, with the continents and seafloor drifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface, examples are Yellowstone, which lies at the end of a chain of extinct calderas, which become progressively older to the west. Another example is the Hawaiian archipelago, where islands become progressively older, boschi, L. Becker, T. W. Steinberger, B. Mantle plumes, Dynamic models and seismic images, break-up spots, Could the Pacific open as a consequence of plate kinematics. Towards A Better Understanding Of Hot Spot Volcanism, formation of Hotspots Raising Hot Spots Large Igneous Provinces Maria Antretter, PhD Thesis, Moving hotspots – Evidence from paleomagnetism and modeling Do Plumes Exist
Hotspot (geology)
–
Over millions of years, the
Pacific Plate has moved over the
Hawaii hotspot, creating
a trail of underwater mountains that stretch across the Pacific
Hotspot (geology)
–
Diagram showing a cross section though the Earth's
lithosphere (in yellow) with
magma rising from the
mantle (in red)
Hotspot (geology)
–
Kilauea is the most active shield volcano in the world. The volcano has erupted nonstop since 1983 and it is part of the
Hawaiian–Emperor seamount chain.
Hotspot (geology)
–
Mauna Loa is a large shield volcano. Its last eruption was in 1984 and it is part of the
Hawaiian–Emperor seamount chain.
8.
Geologic time scale
–
The table of geologic time spans, presented here, agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that Earth is about 4.54 billion years old, the geology or deep time of Earth’s past has been organized into various units according to events which took place in each period. Older time spans, which predate the reliable record, are defined by their absolute age. Some other planets and moons within the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars, dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner. Apart from the Late Heavy Bombardment, events on other planets probably had little influence on the Earth. Construction of a scale that links the planets is, therefore, of only limited relevance to the Earths time scale. The existence, timing, and terrestrial effects of the Late Heavy Bombardment is still debated, the largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs, the terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in Earths history. Geologists qualify these units as early, mid, and late when referring to time, and lower, middle, for example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology. The adjectives are capitalized when the subdivision is formally recognized, and lower case when not, thus early Miocene but Early Jurassic. Geologic units from the time but different parts of the world often look different and contain different fossils. For example, in North America the Lower Cambrian is called the Waucoban series that is subdivided into zones based on succession of trilobites. In East Asia and Siberia, the unit is split into Alexian, Atdabanian. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology, the term Anthropocene is used informally by popular culture and a growing number of scientists to describe the current epoch in which we are living. The term was coined by Paul Crutzen and Eugene Stoermer in 2000 to describe the current time, others say that humans have not even started to leave their biggest impact on Earth, and therefore the Anthropocene hasnt even started yet. Whatever the case, the ICS has not officially approved the term, leonardo da Vinci concurred with Aristotles interpretation that fossils represented the remains of ancient life. The 11th-century Persian geologist Avicenna and the 13th-century Dominican bishop Albertus Magnus extended Aristotles explanation into a theory of a petrifying fluid. Avicenna also first proposed one of the principles underlying geologic time scales, the Chinese naturalist Shen Kuo also recognized the concept of deep time
Geologic time scale
–
Key concepts
Geologic time scale
9.
Oceanic plateau
–
An oceanic plateau is a large, relatively flat submarine region that rises well above the level of the ambient seabed. While many oceanic plateaus are composed of continental crust, and often form a step interrupting the continental slope and these were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the Pacific Northwest of the United States. There are over 180 oceanic plateaus covering an area of 18,486,600 km2, the South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus. Density differences in crustal material largely arise from different ratios of various elements, continental crust has the highest amount of silicon. Oceanic crust has an amount of silicon. Igneous oceanic plateaus have an intermediate between continental and oceanic crust, although they are more mafic than felsic
Oceanic plateau
–
Waves
10.
Indian Ocean
–
The Indian Ocean is the third largest of the worlds oceanic divisions, covering 70,560,000 km2. It is bounded by Asia on the north, on the west by Africa, on the east by Australia, the Indian Ocean is known as Ratnākara, the mine of gems in ancient Sanskrit literature, and as Hind Mahāsāgar, in Hindi. The northernmost extent of the Indian Ocean is approximately 30° north in the Persian Gulf, the oceans continental shelves are narrow, averaging 200 kilometres in width. An exception is found off Australias western coast, where the width exceeds 1,000 kilometres. The average depth of the ocean is 3,890 m and its deepest point is Diamantina Deep in Diamantina Trench, at 8,047 m deep, Sunda Trench has a depth of 7, 258–7,725 m. North of 50° south latitude, 86% of the basin is covered by pelagic sediments. The remaining 14% is layered with terrigenous sediments, glacial outwash dominates the extreme southern latitudes. The major choke points include Bab el Mandeb, Strait of Hormuz, the Lombok Strait, the Strait of Malacca, the Indian Ocean is artificially connected to the Mediterranean Sea through the Suez Canal, which is accessible via the Red Sea. All of the Indian Ocean is in the Eastern Hemisphere and the centre of the Eastern Hemisphere is in this ocean, marginal seas, gulfs, bays and straits of the Indian Ocean include, The climate north of the equator is affected by a monsoon climate. Strong north-east winds blow from October until April, from May until October south, in the Arabian Sea the violent Monsoon brings rain to the Indian subcontinent. In the southern hemisphere, the winds are milder. When the monsoon winds change, cyclones sometimes strike the shores of the Arabian Sea, the Indian Ocean is the warmest ocean in the world. Long-term ocean temperature records show a rapid, continuous warming in the Indian Ocean, Indian Ocean warming is the largest among the tropical oceans, and about 3 times faster than the warming observed in the Pacific. Research indicates that human induced greenhouse warming, and changes in the frequency, among the few large rivers flowing into the Indian Ocean are the Zambezi, Shatt al-Arab, Indus, Godavari, Krishna, Narmada, Ganges, Brahmaputra, Jubba and Irrawaddy River. The oceans currents are controlled by the monsoon. Two large gyres, one in the northern hemisphere flowing clockwise and one south of the equator moving anticlockwise, during the winter monsoon, however, currents in the north are reversed. Deep water circulation is controlled primarily by inflows from the Atlantic Ocean, the Red Sea, north of 20° south latitude the minimum surface temperature is 22 °C, exceeding 28 °C to the east. Southward of 40° south latitude, temperatures drop quickly, surface water salinity ranges from 32 to 37 parts per 1000, the highest occurring in the Arabian Sea and in a belt between southern Africa and south-western Australia
Indian Ocean
–
The economically important
Silk Road (red) and spice
trade routes (blue) were blocked by the
Ottoman Empire in ca. 1453 with the fall of the
Byzantine Empire. This spurred exploration, and a new sea route around Africa was found, triggering the
Age of Discovery.
Indian Ocean
–
Extent of the Indian Ocean according to the
CIA World Factbook
Indian Ocean
–
British heavy cruisers
Dorsetshire and
Cornwall under Japanese air attack and heavily damaged on 5 April 1942
Indian Ocean
–
A
dhow off the coast of Kenya
11.
Myr
–
The Malaysian ringgit is the currency of Malaysia. It is divided into 100 sen, the ringgit is issued by the Bank Negara Malaysia. In modern usage ringgit is used almost solely for the currency, to differentiate between the three currencies, the Malaysian currency is referred to as Ringgit Malaysia, hence the official abbreviation and currency symbol RM. Internationally, the ISO4217 currency code for Malaysian ringgit is MYR, the Malay names ringgit and sen were officially adopted as the sole official names in August 1975. Previously they had been known officially as dollars and cents in English and ringgit and sen in Malay, in the northern states of Peninsular Malaysia, denominations of 10 sen are called kupang in Malay, e. g.50 sen is 5 kupang. On 12 June 1967, the Malaysian dollar, issued by the new bank, Bank Negara Malaysia, replaced the Malaya. The new currency retained all denominations of its predecessor except the $10,000 denomination, and also brought over the colour schemes of the old dollar. In November 1967, five months after the introduction of the Malaysian dollar and this ended on 8 May 1973, when the Malaysian government withdrew from the agreement. The Monetary Authority of Singapore and the Brunei Currency and Monetary Board still maintain the interchangeability of their two currencies, as of 2009, in 1993, the currency symbol RM was introduced to replace the use of the dollar sign $. US$130 and RM1,000 worth of US$260. Despite these measures, the ringgit lost 50% of its value against the US dollar between 1997 and 1998, and suffered general depreciation against other currencies between December 2001 and January 2005. As of 4 September 2008, the ringgit has yet to regain its value circa 2001 against the Singapore dollar, the euro, the Australian dollar, and the British pound. On 21 July 2005, Bank Negara announced the end of the peg to the US dollar immediately after Chinas announcement of the end of the peg to the US dollar. According to Bank Negara, Malaysia allows the ringgit to operate in a float against several major currencies. Following the end of the peg, the ringgit appreciated to as high as 3.16 to the US dollar in April 2008. The ringgit had also enjoyed a period of appreciation against the Hong Kong dollar, the initial stability of the ringgit in the late-2000s had led to considerations to reintroduce the currency to foreign trading. As a result, the US dollar appreciated significantly to close at 3.43 to the MYR as of 4 September 2008, while other major currencies, including the renminbi and Hong Kong dollar, followed suit. The ringgit spiked at 3.73 to the US dollar by March 2009, before recovering to 3.00 to the US dollar by mid-2011. The first series of sen coins were introduced in 1967 in denominations of 1 sen,5 sen,10 sen,20 sen,50 sen, followed by the introduction of the 1 ringgit coin in 1971
Myr
–
The Malaysian ringgit third series coinage and fourth series banknote designs announced in 2011 by Bank Negara Malaysia.
12.
Triple junction
–
A triple junction is the point where the boundaries of three tectonic plates meet. Of the many types of triple junction only a few are stable through time. The first scientific paper detailing the triple junction concept was published in 1969 by W. Jason Morgan, Dan McKenzie, the term had traditionally been used for the intersection of three divergent boundaries or spreading ridges. These three divergent boundaries ideally meet at near 120° angles, in plate tectonics theory during the breakup of a continent, three divergent boundaries form, radiating out from a central point. One of these divergent plate boundaries fails and the two continue spreading to form an ocean. The NE-trending Benue Trough is the arm of this junction. In the years since, the term triple-junction has come to refer to any point where three tectonic plates meet, the junction of the Red Sea, the Gulf of Aden and the East African Rift centered in the Afar Triangle is the only Ridge-Ridge-Ridge triple junction above sea level. The Rodrigues Triple Point is a R-R-R triple junction in the southern Indian Ocean, where the African, the Indo-Australian, the Galapagos Triple Junction is an R-R-R triple junction where the Nazca, the Cocos, and the Pacific Plates meet. The East Pacific Rise extends north and south from this junction and this example is made more complex by the Galapagos Microplate which is a small separate plate on the rise just to the southeast of the triple junction. Chiapas coast off Tapachula where Guatemala, North America and Pacific join and this is pushed eastward by the Cocos plate. On the west coast of North America is another triple junction offshore of Cape Mendocino. To the south, the San Andreas Fault, a fault and transform plate boundary, separates the Pacific Plate. To the north lies the Cascadia subduction zone, where a section of the Juan de Fuca Plate called the Gorda Plate is being subducted under the North American Plate, another transform fault, the Mendocino Fault, runs along the boundary between the Pacific Plate and the Gorda Plate. Where the three intersect is the active, F-F-T Mendocino Triple Junction. The Amurian Plate, the Okhotsk Plate, and the Philippine Sea Plate meet in Japan near Mt. Fuji. The Azores Triple Junction is a triple junction where the boundaries of three tectonic plates intersect, the North American Plate, the Eurasian Plate and the African Plate. The Boso Triple Junction offshore Japan is a T-T-T triple junction between the Okhotsk Plate, Pacific Plate and Philippine Sea Plate, the North Sea is located at the extinct triple junction of three former continental plates of the Palaeozoic era, Avalonia, Laurentia and Baltica. The properties of triple junctions are most easily understood from the purely kinematic point of view where the plates are rigid, no knowledge of the Earths interior or the geological details of the crust are then needed
Triple junction
–
Map of East Africa showing some of the historically active volcanoes(red triangles) and the Afar Triangle (shaded, center) -- a triple junction where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone (USGS).
13.
Gondwana
–
In paleogeography, Gondwana, also Gondwanaland, is the name given to an ancient supercontinent. It is believed to have sutured about 600 to 530 million years ago, Gondwana formed prior to Pangaea, and later became part of it. Around 335 to 250 million years ago Gondwana and Laurasia joined together to form the supercontinent Pangaea, Gondwana then separated from Laurasia in the breakup of Pangaea, drifting farther south after the split. Gondwana itself then also broke apart, the continent of Gondwana was named by Austrian scientist Eduard Suess, after the Gondwana region of central northern India which is derived from Sanskrit for forest of the Gonds. The name had previously used in a geological context, first by H. B. From which the Gondwana sedimentary sequences are also described, for example, the plant family Proteaceae, known only from southern South America, South Africa, Australia, and New Zealand, is considered to have a Gondwanan distribution. This pattern is considered to indicate an archaic, or relict. The assembly of Gondwana was a protracted process, several orogenies led to its final amalgamation 550 to 500 million years ago at the end of the Ediacaran, and into the Cambrian. These include the Brasiliano Orogeny, the East African Orogeny, the Malagasy Orogeny, the final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval, the Cambrian explosion occurred and this is the Famatinian block and it formerly continued the line of the Appalachians southwards. One of the sites of Gondwanan amalgamation was the East African Orogeny. The East African Orogeny at about 650–630 Mya affected a part of Arabia, north-eastern Africa, East Africa. Collins and Windley propose that in this orogeny, Azania collided with the Congo–Tanzania–Bangweulu Block, the later Malagasy orogeny at about 550–515 Mya affected Madagascar, eastern East Africa and southern India. In it, Neoproterozoic India collided with the already combined Azania and Congo–Tanzania–Bangweulu Block, at the same time, in the Kunga Orogeny Neoproterozoic India collided with the Australia/Mawson continent. Other large continental masses, including the core cratons of North America, Europe, when Pangaea broke up, two large masses, Gondwana and Laurasia, were formed. During the late Paleozoic, Gondwana extended from a point at or near the South Pole to near the Equator, across much of Gondwana, the climate was mild. During the Mesozoic, the world was on average warmer than it is today. Gondwana was then host to a variety of flora and fauna for many millions of years
Gondwana
–
Reconstruction showing final stages of assembly of Gondwana, 550 Mya
Gondwana
–
Map of
Pangaea with Laurasia and Gondwana. 200 mya
Gondwana
–
The
Nothofagus plant genus illustrates Gondwanan distribution, having descended from the supercontinent and existing in present-day Australia, New Zealand, New Caledonia, and the
Southern Cone. Fossils have also recently been found in Antarctica.
14.
Antarctica
–
It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14,000,000 square kilometres, it is the fifth-largest continent, for comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages 1.9 km in thickness, Antarctica, on average, is the coldest, driest, and windiest continent, and has the highest average elevation of all the continents. Antarctica is a desert, with precipitation of only 200 mm along the coast. The temperature in Antarctica has reached −89.2 °C, though the average for the quarter is −63 °C. Anywhere from 1,000 to 5,000 people reside throughout the year at the research stations scattered across the continent. Organisms native to Antarctica include many types of algae, bacteria, fungi, plants, protista, vegetation, where it occurs, is tundra. The continent, however, remained neglected for the rest of the 19th century because of its hostile environment, lack of easily accessible resources. In 1895, the first confirmed landing was conducted by a team of Norwegians, Antarctica is a de facto condominium, governed by parties to the Antarctic Treaty System that have consulting status. Twelve countries signed the Antarctic Treaty in 1959, and thirty-eight have signed it since then, the treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear waste disposal, supports scientific research, and protects the continents ecozone. Ongoing experiments are conducted by more than 4,000 scientists from many nations, the name Antarctica is the romanised version of the Greek compound word ἀνταρκτική, feminine of ἀνταρκτικός, meaning opposite to the Arctic, opposite to the north. Aristotle wrote in his book Meteorology about an Antarctic region in c.350 B. C, marinus of Tyre reportedly used the name in his unpreserved world map from the 2nd century A. D. Before acquiring its present geographical connotations, the term was used for locations that could be defined as opposite to the north. For example, the short-lived French colony established in Brazil in the 16th century was called France Antarctique, the first formal use of the name Antarctica as a continental name in the 1890s is attributed to the Scottish cartographer John George Bartholomew. Antarctica has no population and there is no evidence that it was seen by humans until the 19th century. Explorer Matthew Flinders, in particular, has credited with popularising the transfer of the name Terra Australis to Australia. Cook came within about 120 km of the Antarctic coast before retreating in the face of ice in January 1773. The first confirmed sighting of Antarctica can be narrowed down to the crews of ships captained by three individuals, according to various organisations, ships captained by three men sighted Antarctica or its ice shelf in 1820, von Bellingshausen, Edward Bransfield, and Nathaniel Palmer
Antarctica
–
Adelie penguins in Antarctica
Antarctica
–
Antarctica
Antarctica
–
Painting of
James Weddell 's second expedition in 1823, depicting the brig Jane and the cutter Beaufroy.
Antarctica
–
Nimrod Expedition South Pole Party (left to right):
Wild,
Shackleton,
Marshall and
Adams
15.
South America
–
South America is a continent located in the western hemisphere, mostly in the southern hemisphere, with a relatively small portion in the northern hemisphere. It may also be considered a subcontinent of the Americas, which is the used in nations that speak Romance languages. The reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean, North America and it includes twelve sovereign states, a part of France, and a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands, Trinidad and Tobago, South America has an area of 17,840,000 square kilometers. Its population as of 2005 has been estimated at more than 371,090,000, South America ranks fourth in area and fifth in population. Brazil is by far the most populous South American country, with more than half of the population, followed by Colombia, Argentina, Venezuela. In recent decades Brazil has also concentrated half of the regions GDP and has become a first regional power, most of the population lives near the continents western or eastern coasts while the interior and the far south are sparsely populated. Most of the continent lies in the tropics, the continents cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the majority of South Americans speak Portuguese or Spanish. South America occupies the portion of the Americas. The continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border. Almost all of mainland South America sits on the South American Plate, South Americas major mineral resources are gold, silver, copper, iron ore, tin, and petroleum. These resources found in South America have brought high income to its countries especially in times of war or of rapid growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity often has hindered the development of diversified economies and this is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth, South America is home to many interesting and unique species of animals including the llama, anaconda, piranha, jaguar, vicuña, and tapir. The Amazon rainforests possess high biodiversity, containing a proportion of the Earths species. Brazil is the largest country in South America, encompassing around half of the land area
South America
–
A composite relief image of South America.
South America
–
South America
South America
–
Cuernos del Paine in Chile (left) and
Morro do Chapéu in Brazil (right) serve to illustrate the diversity of landscapes in South America. Click to enlarge.
South America
16.
Africa
–
Africa is the worlds second-largest and second-most-populous continent. At about 30.3 million km² including adjacent islands, it covers 6% of Earths total surface area and 20.4 % of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the human population. The continent includes Madagascar and various archipelagos and it contains 54 fully recognized sovereign states, nine territories and two de facto independent states with limited or no recognition. Africas population is the youngest amongst all the continents, the age in 2012 was 19.7. Algeria is Africas largest country by area, and Nigeria by population, afarensis, Homo erectus, H. habilis and H. ergaster – with the earliest Homo sapiens found in Ethiopia being dated to circa 200,000 years ago. Africa straddles the equator and encompasses numerous climate areas, it is the continent to stretch from the northern temperate to southern temperate zones. Africa hosts a diversity of ethnicities, cultures and languages. In the late 19th century European countries colonized most of Africa, Africa also varies greatly with regard to environments, economics, historical ties and government systems. However, most present states in Africa originate from a process of decolonization in the 20th century, afri was a Latin name used to refer to the inhabitants of Africa, which in its widest sense referred to all lands south of the Mediterranean. This name seems to have referred to a native Libyan tribe. The name is connected with Hebrew or Phoenician ʿafar dust. The same word may be found in the name of the Banu Ifran from Algeria and Tripolitania, under Roman rule, Carthage became the capital of the province of Africa Proconsularis, which also included the coastal part of modern Libya. The Latin suffix -ica can sometimes be used to denote a land, the later Muslim kingdom of Ifriqiya, modern-day Tunisia, also preserved a form of the name. According to the Romans, Africa lay to the west of Egypt, while Asia was used to refer to Anatolia, as Europeans came to understand the real extent of the continent, the idea of Africa expanded with their knowledge. 25,4, whose descendants, he claimed, had invaded Libya, isidore of Seville in Etymologiae XIV.5.2. Suggests Africa comes from the Latin aprica, meaning sunny, massey, in 1881, stated that Africa is derived from the Egyptian af-rui-ka, meaning to turn toward the opening of the Ka. The Ka is the double of every person and the opening of the Ka refers to a womb or birthplace
Africa
–
Map of Africa
Africa
–
Africa
Africa
–
Lucy, an
Australopithecus afarensis skeleton discovered on November 24, 1974, in the
Awash Valley of
Ethiopia 's
Afar Depression
Africa
–
Colossal statues of
Ramesses II at
Abu Simbel, Egypt, date from around 1400 BC.
17.
Northeast Georgia Rise
–
The Northeast Georgia Rise is an oceanic plateau located in the South Atlantic Ocean northeast of South Georgia Island and west of the Falkland Plateau. The rise is separated from South Georgia Island by the Northeast Georgia Passage, the Georgia Basin surrounds the northern end of the rise. The Agulhas-Falkland Fracture Zone stretches across the Atlantic north of the Northeast Georgia Rise, a group of small seamounts north of the rise are aligned with a gap in the AFFZ. East of this gap the AFFZ is a ridge with an average height of 2,500 m. On the eastern flank of the rise is a prominent ridge and it has the same orientation as the southeastern part of the rise. It is a basement-feature in which bottom-water have scoured a channel, both the Northeast Georgia Rise and the Islas Orcadas Rise east of it, are seemingly dissected by transverse valleys that extend to the fracture zones of the Mid-Atlantic Ridge. The Northeast Georgia Rise is made of oceanic crust that formed when Africa,100 Ma the Northeast Georgia Rise was part of the Agulhas Plateau-Northeast Georgia Rise-Maud Rise large igneous province in what today is the southwestern-most Indian Ocean south of South Africa. This LIP, often called the southeast African LIP, formed at the junction where Gondwana passed over the Bouvet Hotspot and broke-up into Antarctica, South America. Northeast Georgia Rise and the Agulhas Plateau were always located on different tectonic plates, because of this, these two plateaus can be used to reconstruct the movements of the two plates from the formation of the southeast African LIP. Northeast Georgia rise collided with the South Georgia microcontinental block about 10 Ma which caused the uplift of this block, the collision coincided with the termination of spreading at the West Scotia Sea and resulted in a bathymetric obstacle that still steers the Antarctic Circumpolar Current northward. Two or more episodes of deformation have modified the topography of the ridge, as a part of the Scotia Plate, the South Georgia block has been moving eastward. In the Scotia Sea the Antarctic Circumpolar Current is deflected north by the South Scotia Ridge and it then widens extensively before passing over the North Scotia Ridge. North of South Georgia the southern boundary of the ACC is retroflected around the Northeast Georgia Rise, the Southern Antarctic Circumpolar Current Front meanders across the Scotia Sea from the western shelf of the Antarctic Peninsula to the southwestern side of South Georgia. From there SACCF wraps the island anti-cyclonically, retroflects north of it, the retroflection north of the island and across the rise shows a strong seasonal variability but SACCF remains constrained by these bathymetric obstacles. Weddell Sea Deep Water circulates cyclonically in the Weddell Gyre from where it escapes through gaps in the South Scotia Ridge and it then flows across the Scotia Sea which it can only escape through the Georgia Passage. WSDW can reach the Georgia Basin by two routes, either by circumnavigating the Northeast Georgia Rise on its side or by passing through the Northeast Georgia Passage
Northeast Georgia Rise
–
Centred in the Georgia Basin, Northeast Georgia Rise is located northeast of South Georgia, west of Islas Orcadas Rise, south the Falkland Ridge and north of the
South Sandwich Trench. North or Northwest Georgia Rise, barely visible just north of South Georgia, also affects ocean circulation but has a different tectonic history.
18.
Bouvet Island
–
Bouvet Island is an uninhabited subantarctic high island and dependency of Norway located in the South Atlantic Ocean at 54°25. 8′S 3°22. 8′E. The island has an area of 49 square kilometres, of which 93 percent is covered by a glacier, the centre of the island is an ice-filled crater of an inactive volcano. Some skerries and one island, Larsøya, lie along the coast. Nyrøysa, created by a slide in the late 1950s, is the only easy place to land and is the location of a weather station. The island was first spotted on 1 January 1739 by Jean-Baptiste Charles Bouvet de Lozier, after whom it was later named and he recorded inaccurate coordinates and the island was not sighted again until 1808, when the British whaler captain James Lindsay named it Lindsay Island. The first claim of landing, although disputed, was by Benjamin Morrell, in 1825, the island was claimed for the British Crown by George Norris, who named it Liverpool Island. He also reported Thompson Island as nearby, although this was shown to be a phantom island. The first Norvegia expedition landed on the island in 1927 and claimed it for Norway, at this time the island was named Bouvet Island, or Bouvetøya in Norwegian. After a dispute with the United Kingdom, it was declared a Norwegian dependency in 1930 and it became a nature reserve in 1971. The island was discovered on 1 January 1739 by Jean-Baptiste Charles Bouvet de Lozier, commander of the French ships Aigle and this was the first time that land had been spotted south of the 50th parallel south. Bouvet, who was searching for a large southern continent, spotted the island through the fog. He was not able to land and did not circumnavigate his discovery and his plotting of its position was inaccurate, leading several expeditions to fail to find the island again. James Cooks second voyage set off from Cape Verde on 22 November 1772 to find Cape Circoncision, the next expedition to spot the island was in 1808 by James Lindsay, captain of the Samuel Enderby & Sons whaler Snow Swan. They reached the island and recorded its position, though they were unable to land, Lindsay could confirm that the cape was indeed an island. The next expedition to arrive at the island was American Benjamin Morrell, Morrell, by his own account, found the island without difficulty before landing and hunting 196 seals. In his subsequent lengthy description, Morrell does not mention the islands most obvious physical feature and this has caused some commentators to doubt whether he actually visited the island. On 10 December 1825, SE&Ss George Norris, master of the Sprightly, landed on the island, named it Liverpool Island and claimed it for the British Crown and George IV on 16 December. The next expedition to spot the island was Joseph Fuller and his ship Francis Allyn in 1893, german Carl Chuns Valdivia expedition arrived at the island in 1898
Bouvet Island
–
Southeast coast of Bouvet Island in 1898
Bouvet Island
–
Flag
Bouvet Island
–
The first hut, built on
Kapp Circoncision, in 1929.
Bouvet Island
–
Glacier on Bouvet Island's west coast
19.
Bruce C. Heezen
–
Bruce Charles Heezen was an American geologist. He worked with oceanographic cartographer Marie Tharp at Columbia University to map the Mid-Atlantic Ridge in the 1950s, Heezen was born in Vinton, Iowa. An only child, he moved at age six with his parents to Muscatine, Iowa and he received his B. A. from the University of Iowa in 1947. He received his M. A. in 1952 and a Ph. D in 1957 from Columbia University, Heezen collaborated extensively with cartographer Marie Tharp. Heezen died of an attack in 1977 while on a research cruise to study the Mid-Atlantic Ridge near Iceland aboard the NR-1 submarine. Heezen was christened in honor of him in 1999, Bruce Heezen explaining formation of oil traps on the ocean floor on YouTube Bruce Heezen explaining turbidity currents on YouTube
Bruce C. Heezen
–
Marie Tharp and Bruce Heezen
20.
Marie Tharp
–
Marie Tharp was an American geologist and oceanographic cartographer who, in partnership with Bruce Heezen, created the first scientific map of the entire ocean floor. Tharps work revealed the presence of the Mid-Atlantic Ridge, causing a shift in earth science that led to acceptance of the theories of plate tectonics. Tharp was born in Ypsilanti, Michigan and her mother, Bertha, was an instructor in German and Latin, her father, William, made soil classification maps for the U. S. Department of Agriculture. Tharp graduated from Ohio University in 1943 with bachelors degrees in English and music, moving to New York in 1948, Tharp was employed by Maurice Ewing at the Lamont Geological Laboratory at Columbia University, initially as a general drafter. There Tharp met Heezen and in early work together used photographic data to locate downed aircraft from World War II, later, they began working together to map the topography of the ocean floor. Restricted from conducting research at sea early in her due to her gender. Tharp independently used data collected from the Woods Hole Oceanographic Institutions research ship Atlantis and her work with Heezen represented the first systematic attempt to map the entire ocean floor. Tharp and Heezen published their first physiographic map of the North Atlantic in 1957, collaborating with the Austrian landscape painter Heinrich Berann, they published their map of the entire ocean floor in 1977. But under Tharps direction Heezen eventually turned to the theories of plate tectonics. Tharp continued to serve on the faculty of Columbia University until 1983, after which she operated a business in South Nyack. Tharp donated her map collection and notes to the Map and Geography Division of the Library of Congress in 1995, in 2001, Tharp was awarded the first annual Lamont-Doherty Heritage Award at her home institution for her lifes work as a pioneer of oceanography. Tharp died of cancer in Nyack, New York on August 23,2006, in 2009, Ocean in Google Earth included the Marie Tharp Historical Map layer, to allow people to view Tharps map using the Google Earth interface. In 2013, author Hali Felt published a biography of Marie Tharp entitled Soundings and it was cited by the New York Times for its standing as an eloquent testament both to Tharp’s importance and to Felt’s powers of imagination. The Marie Tharp Fellowship is a competitive academic visiting fellowship awarded to women to work with researchers at Columbia Universitys Earth Institute, Heezen, B C, Bunce, Elizabeth T, Hersey, J B, Tharpe, Marie. Tectonic fabric of the atlantic and indian oceans and continental drift, philosophical Transactions of the Royal Society of London, Series A, Mathematical and Physical Sciences. Tharpe, Marie, Friedman, Gerald M. Mapping the world ocean floor, c250 Celebrates 250 Columbians Ahead of Their Time, Entry on Marie Tharp. Marie Tharp Honored at Women Pioneers Seminar, the Earth Institute at Columbia University. The Earth Institute at Columbia University, Marie Tharp, Pioneering Mapmaker of the Ocean Floor, Dies
Marie Tharp
–
Tharp and
Bruce Heezen
21.
Agulhas Bank
–
The Agulhas Bank is a broad, shallow part of the southern African continental shelf which extends up to 250 km south of Cape Agulhas before falling steeply to the abyssal plain. It is the region where the warm Indian Ocean and the cold Atlantic Ocean meet. This convergence leads to treacherous sailing conditions, accounting for numerous wrecked ships in the area over the years, however the meeting of the oceans here also fuels the nutrient cycle for marine life, making it one of the best fishing grounds in South Africa. The Agulhas Bank stretches approximately 800 km along the African coast, from off Cape Peninsula to Port Alfred, the bank is 50 m deep near the coast and reaches 200 m before dropping steeply to 1,000 m on its southern edge. The shelf spans an area of 116,000 km2 with a mean depth slightly over 100 m, the National Spatial Biodiversity Assessment 2004 recognised 34 biozones nested within 9 bioregions. The National Biodiversity Assessment 2011 replaced these ecozones and biozones with the terms ecoregions, in 2011, the Agulhas Ecoregion was divided into four distinct ecozones, Agulhas inshore, Agulhas inner shelf, Agulhas outer shelf, and Agulhas shelf edge. 33 different benthic habitats types were identified on the Agulhas Bank, there are dozens of warm temperate reefs along the coast of the Agulhas Ecoregion spanning from 5–30 m below sea level. Many rocky sub-tidal reefs are of aeolianite or sandstone origin, but granite, quartzite, the Agulhas reefs are very heterogeneous and include several possible different sub-types. Some of the reefs are protected areas, but only a few of those protected areas include protection from fishing. The Agulhas Bank is a boundary between ocean currents from the Atlantic Ocean, Indian Ocean, and Southern Ocean, resulting in one of the most turbulent waters of the world oceans. The Agulhas Current flows south along the African east-coast and along the edge of the bank. It then retroflects back into the Indian Ocean south-west of the bank and this retroflection results in intense eddy activities such as meanders, eddies, and filaments. In upper layer water, the Agulhas rings and eddies move warm and salty water into the large South Atlantic gyre, in the lower ocean layers water is transported in the opposite direction. Cyclonic eddies is another source of edge upwelling west of Port Elisabeth, plumes of warm surface water migrate onto the bank along its eastern edge, providing subtropical surface water from the Indian Ocean. In summer, easterly winds can intermittently drive coastal upwelling along the South African south coast, as the current is diverged away from the coast, dynamic processes draws an onshore Ekman layer of cold water from below the warm shelf-edge flow. In spring and summer, at a depth of 100 m, in summer, there is mixture of subtropical water separated by thermoclines from cool waters, but there is a considerable seasonal variation. On the shelf, bottom waters exhibit characteristics of the central Indian Ocean in the east, as the Agulhas Current flows south along the African east coast, it tends to bulge inshore frequently, a deviation from the currents normal path known as Agulhas Current meanders. These bulges are occasionally followed by a much larger offshore bulge, Natal pulses move along the coast at 20 km per day
Agulhas Bank
–
Map of the Agulhas Bank centred on the Outeniqua Basin
Agulhas Bank
–
Light blue plankton in a 150 km (93 mi) wide anti-cyclonic (counter-clockwise) Agulhas ring 800 km (500 mi) south the South Africa. Such eddies, among the largest in the world, are peeled off the Agulhas Current on the eastern edge of the Agulhas Bank.
Agulhas Bank
–
The Agulhas Bank relative to the Agulhas Ridge,
Basin, and
Plateau
Agulhas Bank
–
Papery burnupena in
False Bay
22.
Basement (geology)
–
In the same way, the sediments or sedimentary rocks on top of the basement can be called a cover or sedimentary cover. Basement rock is the foundation of ancient, and oldest metamorphic and igneous rock that forms the crust of continents. Basement rock is contrasted to overlying sedimentary rocks which are laid down on top of the basement rocks after the continent was formed, the sedimentary rocks which may be deposited on top of the basement usually form a relatively thin veneer, but can be more than 3 miles thick. The basement rock of the crust can be 20–30 miles thick, the basement rock can be located under layers of sedimentary rock, or be visible at the surface. Basement rock is visible at the bottom of the Grand Canyon, consisting of 1. 7-2 billion year old granite, an extensive cross section of sedimentary rocks laid down on top of it through the ages is visible as well. The basement rocks of the continental crust tend to be older than the oceanic crust. The oceanic crust can be from 0-250 million years in age, the basement rocks are often highly metamorphosed and complex. They may consist of different types of rock - volcanic, intrusive igneous. They may also contain fragments of oceanic crust that became wedged between plates when a terrane was accreted to the edge of the continent, any of this material may be folded, refolded and metamorphosed. New igneous rock may freshly intrude into the crust from underneath, or may form underplating, much of the basement rock may have originally been oceanic crust, but it was highly metamorphosed and converted into continental crust via a series of events. A typical pattern is as follows and this produces an oceanic chain of volcanoes, like Japan. This volcanism causes metamorphosis of rocks, intrusions of magma that produce such as granite. This tends to make the crust lighter and thicker, as a result making it immune to subduction, oceanic crust can be subducted, while continental crust cannot. Eventually, the subduction of the oceanic crust can bring the volcano chain close to a continent. When the overriding plate collides with the continent, instead of being subducted, it is accreted to the edge of the continent and becomes a part of that continent. In this manner, continents can grow over time as new terranes are accreted to their edges, as such, the basement rock can become younger going closer to the edge of the continent. There are exceptions of however, such as exotic terranes, exotic terranes are pieces or fragments of other continents that have broken off their original parent continent and have become accreted to a different continent. For instance, Pangea consisted of most of the Earths continents being accreted into one giant supercontinent, most continents indeed have several continental cratons, in other words they are made up of the accretion of many smaller continents, such as Asia, Africa, and Europe
Basement (geology)
–
Gneiss outcrop, basement rock,
Scotland.
23.
Oceanic crust
–
Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. The crust overlies the solidified and uppermost layer of the mantle, the crust and the solid mantle layer together constitute oceanic lithosphere. Oceanic crust is the result of erupted mantle material originating from below the plate, cooled and in most instances and this occurs mostly at mid-ocean ridges, but also at scattered hotspots, and also in rare but powerful occurrences known as flood basalt eruptions. It is primarily composed of rocks, or sima, which is rich in iron. Although a complete section of oceanic crust has not yet been drilled, Oceanic crust is significantly simpler than continental crust and generally can be divided in three layers. Layer 1 is on an average 0.4 km thick and it consists of unconsolidated or semiconsolidated sediments, usually thin or even not present near the mid-ocean ridges but thickens farther away from the ridge. Layer 3 is formed by slow cooling of magma beneath the surface and consists of coarse grained gabbros and it constitutes over two-thirds of oceanic crust volume with almost 5 km thickness. The most voluminous volcanic rocks of the floor are the mid-oceanic ridge basalts. These rocks have low concentrations of large ion lithophile elements, light rare earth elements, volatile elements, there can be found basalts enriched with incompatible elements, but they are rare and associated with mid-ocean ridge hot spots such as surroundings of Galapagos Islands, the Azores and Iceland. Oceanic crust is continuously being created at mid-ocean ridges, as plates diverge at these ridges, magma rises into the upper mantle and crust. As it moves away from the ridge, the lithosphere becomes cooler and denser, the youngest oceanic lithosphere is at the oceanic ridges, and it gets progressively older away from the ridges. As the mantle rises it cools and melts, as the pressure decreases, the amount of melt produced depends only on the temperature of the mantle as it rises. Hence most oceanic crust is the same thickness, an example of this is the Gakkel Ridge under the Arctic Ocean. Thicker than average crust is found above plumes as the mantle is hotter and hence it crosses the solidus and melts at a depth, creating more melt. An example of this is Iceland which has crust of thickness ~20 km, the oceanic lithosphere subducts at what are known as convergent boundaries. These boundaries can exist between oceanic lithosphere on one plate and oceanic lithosphere on another, or between oceanic lithosphere on one plate and continental lithosphere on another, in the second situation, the oceanic lithosphere always subducts because the continental lithosphere is less dense. The subduction process consumes older oceanic lithosphere, so oceanic crust is more than 200 million years old. The process of super-continent formation and destruction via repeated cycles of creation and destruction of oceanic crust is known as the Wilson cycle, the oldest large scale oceanic crust is in the west Pacific and north-west Atlantic - both are about up to 180-200 million years old
Oceanic crust
–
Colors indicate the age of oceanic lithosphere, wherein red indicates the youngest age, and blue indicates the oldest age. The lines represent tectonic plates.
24.
Continental crust
–
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because its composition is more felsic compared to the oceanic crust. The continental crust consists of layers, with a bulk composition that is intermediate to felsic. The average density of continental crust is about 2.7 g/cm3, less dense than the material that makes up the mantle. Continental crust is less dense than oceanic crust, whose density is about 2.9 g/cm3. At 25 to 70 km, continental crust is thicker than oceanic crust. About 40% of Earths surface is occupied by continental crust. It makes up about 70% of the volume of Earths crust, because the surface of continental crust mainly lies above sea level, its existence allowed land life to evolve from marine life. There is little evidence of continental crust prior to 3.5 Ga, all continental crust ultimately derives from the fractional differentiation of oceanic crust over many eons. This process has been and continues today primarily as a result of the associated with subduction. In contrast to the persistence of continental crust, the size, shape, different tracts rift apart, collide and recoalesce as part of a grand supercontinent cycle. There are currently about 7 billion cubic kilometers of continental crust, the relative permanence of continental crust contrasts with the short life of oceanic crust. Because continental crust is less dense oceanic crust, when active margins of the two meet in subduction zones, the oceanic crust is typically subducted back into the mantle. Continental crust is rarely subducted.01 Ga, whereas the oldest oceanic crust is from the Jurassic, Continental crust and the rock layers that lie on and within it are thus the best archive of Earths history. The height of mountain ranges is usually related to the thickness of crust and this results from the isostasy associated with orogeny. The crust is thickened by the compressive forces related to subduction or continental collision, the buoyancy of the crust forces it upwards, the forces of the collisional stress balanced by gravity and erosion. This forms a keel or mountain root beneath the mountain range, the thinnest continental crust is found in rift zones, where the crust is thinned by detachment faulting and eventually severed, replaced by oceanic crust. The edges of continental fragments formed this way are termed passive margins, igneous rock may also be underplated to the underside of the crust, i. e. adding to the crust by forming a layer immediately beneath it
Continental crust
–
The thickness of
Earth's crust (km)
25.
South Georgia Island
–
South Georgia is an island in the South Atlantic that is part of the British Overseas territory of South Georgia and the South Sandwich Islands. South Georgia is 167.4 kilometres long and 1.4 to 37 km wide. The Island of South Georgia is said to have been first sighted in 1675 by Anthony de la Roché, a London merchant and it was sighted by a commercial Spanish ship named León operating out of Saint-Malo on 28 June or 29 June 1756
South Georgia Island
–
Central South Georgia
Cumberland Bay –
Thatcher Peninsula with
King Edward Cove (
Grytviken) –
Allardyce Range, featuring the summit of
Mount Paget. (NASA imagery)
South Georgia Island
–
Flag
South Georgia Island
–
Map by James Cook (1777, south facing upwards)
South Georgia Island
–
The church at
Grytviken
26.
Geoid
–
The geoid is the shape that the surface of the oceans would take under the influence of Earths gravity and rotation alone, in the absence of other influences such as winds and tides. This surface is extended through the continents, all points on a geoid surface have the same gravity potential energy. The geoid can be defined at any value of gravitational potential such as within the earths crust or far out in space and it does not correspond to the actual surface of Earths crust, but to a surface which can only be known through extensive gravitational measurements and calculations. It is often described as the true figure of the Earth. The surface of the geoid is higher than the reference ellipsoid wherever there is a gravity anomaly. The geoid surface is irregular, unlike the ellipsoid which is a mathematical idealized representation of the physical Earth. Although the physical Earth has excursions of +8,848 m and −429 m, If the ocean surface were isopycnic and undisturbed by tides, currents, or weather, it would closely approximate the geoid. The permanent deviation between the geoid and mean sea level is called ocean surface topography, If the continental land masses were criss-crossed by a series of tunnels or canals, the sea level in these canals would also very nearly coincide with the geoid. This means that when traveling by ship, one does not notice the undulations of the geoid, the vertical is always perpendicular to the geoid. Likewise, spirit levels will always be parallel to the geoid, a long voyage, indicate height variations, even though the ship will always be at sea level. This is because GPS satellites, orbiting about the center of gravity of the Earth, to obtain ones geoidal height, a raw GPS reading must be corrected. Conversely, height determined by spirit leveling from a tidal measurement station, as in land surveying. Modern GPS receivers have a grid implemented inside where they obtain the height over the World Geodetic System ellipsoid from the current position. Then they are able to correct the height above WGS ellipsoid to the height above WGS84 geoid, in that case when the height is not zero on a ship it is due to various other factors such as ocean tides, atmospheric pressure and local sea surface topography. The gravitational field of the earth is neither perfect n If that perfect sphere were then covered in water, instead, the water level would be higher or lower depending on the particular strength of gravity in that location. Spherical harmonics are used to approximate the shape of the geoid. The current best such set of spherical harmonic coefficients is EGM96, the geoid is a particular equipotential surface, and is somewhat involved to compute. The gradient of this also provides a model of the gravitational acceleration
Geoid
–
Three-dimensional visualization of geoid undulations, using
units of gravity.
Geoid
–
Geodesy
27.
Magsat
–
Magsat spacecraft was launched in the fall of 1979 and ended in the spring of 1980. The mission was to map the Earths magnetic field, the satellite had two magnetometers, the scalar and vector magnetometers gave Magsat a capability beyond that of any previous spacecraft. Extended by a boom, the magnetometers were distanced from the magnetic field created by the satellite. After launch the payload was brought to an orbit of 96. 8° facing the Sun as the Earth rotated underneath and it was kept in a close Earth orbit, with vector magnetometers capable of sensing magnetic fields closer to Earths surface. The data collected by this allowed a 3D-mapping of the Earths magnetic interior as never seen before. In combination with a satellite, Ørsted, it has been an essential component for explaining the current declining state of the Earths magnetic field. On October 30,1979 Magsat was launched from pad SLC-5 at Vandenberg AFB in California on a Scout II rocket bearing 97° in a dusk to dawn orbit, the spacecraft was placed in an orbit with a perigee of 350 kilometres and an apogee of 550 kilometres. After reaching orbit, its boom was extended outward by 6 metres. Two star cameras were used to define the position of the relative to Earth. The orbit allowed the satellite to map a majority of the Earths surfaces except the geographic poles, the satellite decayed from orbit on June 11,1980. A stored memory of 2.8 kilobytes in PROMs with 1 K bytes of random access memory provided the program and working space for the microprocessor. Other integrated circuits chips of the CDP1800 family of circuits were used, including the CDP1852 interface circuit. Three families of circuits were considered for the system design. Software for the project was developed with an in-house APL-generated 1802 cross-assembler running on IBM 360/370 mainframe computers, one of the biggest is that the motion of a metallic object tends to create a magnetic field. One study after the mission found a nonlinear fluxgate response when exposed to greater than 5000 mT. The applied field had to be transverse to the axis of the magnetometer, the design was improved by creating a feedback relay over a spherical design. This was the used on later spacecraft. This configuration magnetometer was also used on the Magnetometer of the Jupiter orbiter Juno
Magsat
–
Magsat
Magsat
–
Modeled Earth magnetic fields, data created by satellites with sensitive magnetometers
28.
Gravity anomaly
–
A gravity anomaly is the difference between the observed acceleration of free fall, or gravity, on a planets surface, and the corresponding value predicted from a model of the planets gravity field. Typically the model is based on simplifying assumptions, such as that, under its self-gravitation and rotational motion, the planet assumes the figure of an ellipsoid of revolution. Gravity on the surface of this ellipsoid is given by a simple formula which only contains the latitude. As such, gravity anomalies describe the variations of the gravity field around the model field. These anomalies are thus of substantial geophysical and geological interest, cleanly extracting the response to the local sub-surface geology is the typical goal of applied geophysics. Lateral variations in gravity anomalies are related to anomalous density distributions within the Earth, Gravity measures help us to understand the internal structure of the planet. Synthetic calculations show that the gravity signature of a thickened crust is negative and larger in absolute value. The Bouguer anomalies usually are negative in the mountains because they involve reducing out the attraction of the mountain mass, typical anomalies in the Central Alps are −150 milligals. Rather local anomalies are used in applied geophysics, if they are positive, at scales between entire mountain ranges and ore bodies, Bouguer anomalies may indicate rock types. For example, the northeast-southwest trending high across central New Jersey represents a graben of Triassic age largely filled with dense basalts, salt domes are typically expressed in gravity maps as lows, because salt has a low density compared to the rocks the dome intrudes. Anomalies can help to distinguish sedimentary basins whose fill differs in density from that of the surrounding region - see Gravity Anomalies of Britain, in geodesy and geophysics, the usual theoretical model is the gravity on the surface of a reference ellipsoid such as WGS84. The elevation of the point where each gravity measurement was taken must be reduced to a reference datum to compare the whole profile and this is called the Free-air Correction, and when combined with the removal of theoretical gravity leaves the free-air anomaly. Simply, we have to correct for the effects of any material between the point where gravimetry was done and the geoid, to do this we model the material in between as being made up of an infinite number of slabs of thickness t. These slabs have no lateral variation in density, but each slab may have a different density than the one above or below it and this is called the Bouguer correction. A terrain correction, computed from a structure, accounts for the effects of rapid lateral change in density, e. g. edge of plateau, cliffs, steep mountains. For these reductions, different methods are used, The gravity changes as we move away from the surface of the Earth, for this reason, we must compensate with the free-air anomaly, application of the normal gradient 0.3086 mGal/m, but no terrain model. This anomaly means a shift of the point, together with the whole shape of the terrain. This simple method is ideal for many geodetic applications, simple Bouguer anomaly, downward reduction just by the Bouguer gradient
Gravity anomaly
–
(Bouguer) gravity anomaly map of the state of
New Jersey (USGS)
Gravity anomaly
–
Gravity and
geoid anomalies caused by various crustal and lithospheric thickness changes relative to a reference configuration. All settings are under local
isostatic compensation.
29.
Magnetic anomaly
–
In geophysics, a magnetic anomaly is a local variation in the Earths magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material, the magnetic variation in successive bands of ocean floor parallel with mid-ocean ridges is important evidence supporting the theory of seafloor spreading, central to plate tectonics. Magnetic anomalies are generally a fraction of the magnetic field. The total field ranges from 25,000 to 65,000 nanoteslas, to measure anomalies, magnetometers need a sensitivity of 10 nT or less. There are three types of magnetometer used to measure magnetic anomalies, The fluxgate magnetometer was developed during World War II to detect submarines. It measures the component along an axis of the sensor. On land, it is oriented vertically, while in aircraft, ships. It measures the field continuously, but drifts over time. One way to correct for drift is to take repeated measurements at the place during the survey. The proton precession magnetometer measures the strength of the field but not its direction, each measurement takes a second or more. It is used in most ground surveys except for boreholes and high-resolution gradiometer surveys, optically pumped magnetometers, which use alkali gases have high sample rates and sensitivities of 0.001 nT or less, but are more expensive than the other types of magnetometers. They are used on satellites and in most aeromagnetic surveys, in ground-based surveys, measurements are made at a series of stations, typically 15 to 60 m apart. Usually a proton magnetometer is used and it is often mounted on a pole. Raising the magnetometer reduces the influence of small objects that were discarded by humans. To further reduce unwanted signals, they do not carry such as keys. In addition, objects such as vehicles, railway lines. If some such contaminant is overlooked, it shows up as a sharp spike in the anomaly. The main application for ground-based surveys is detailed search for minerals, airborne magnetic surveys are often used in oil surveys to provide preliminary information for seismic surveys
Magnetic anomaly
–
Satellite measurements of the radial magnetic field on Mars.
Magnetic anomaly
–
This helicopter is equipped with a magnetometer array. It flies six feet above ground at speeds of 30 to 40 mph.
(PDF). Tectonophysics. 609: 675–689. doi:10.1016/j.tecto.2013.08.033. Retrieved 13 November 2016.
