1.
Lithosphere
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A lithosphere is the rigid, outermost shell of a terrestrial-type planet or natural satellite that is defined by its rigid mechanical properties. On Earth, it is composed of the crust and the portion of the mantle that behaves elastically on time scales of thousands of years or greater. The outermost shell of a planet, the crust, is defined on the basis of its chemistry. Earths lithosphere includes the crust and the uppermost mantle, which constitute the hard, the lithosphere is subdivided into tectonic plates. The uppermost part of the lithosphere that chemically reacts to the atmosphere, hydrosphere and biosphere through the forming process is called the pedosphere. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, the study of past and current formations of landscapes is called geomorphology. The concept of the lithosphere as Earth’s strong outer layer was described by A. E. H, love in his 1911 monograph Some problems of Geodynamics and further developed by Joseph Barrell, who wrote a series of papers about the concept and introduced the term lithosphere. The concept was based on the presence of significant gravity anomalies over continental crust and these ideas were expanded by Reginald Aldworth Daly in 1940 with his seminal work Strength and Structure of the Earth and have been broadly accepted by geologists and geophysicists. The temperature at which olivine begins to deform viscously is often used to set this isotherm because olivine is generally the weakest mineral in the upper mantle, the mantle part of the lithosphere consists largely of peridotite. The crust is distinguished from the mantle by the change in chemical composition that takes place at the Moho discontinuity. Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle and is denser than continental lithosphere, oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick, the thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time. H ∼2 κ t Here, h is the thickness of the mantle lithosphere, κ is the thermal diffusivity for silicate rocks. The age is equal to L/V, where L is the distance from the spreading centre of mid-oceanic ridge. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years and this is because the chemically differentiated oceanic crust is lighter than asthenosphere, but thermal contraction of the mantle lithosphere makes it more dense than the asthenosphere. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones, geoscientists can directly study the nature of the subcontinental mantle by examining mantle xenoliths brought up in kimberlite, lamproite, and other volcanic pipes. The histories of these xenoliths have been investigated by many methods, such studies have confirmed that mantle lithospheres below some cratons have persisted for periods in excess of 3 billion years, despite the mantle flow that accompanies plate tectonics. Cryosphere Geosphere Kola Superdeep Borehole Plate tectonics Solid Earth Chernicoff, Stanley, Whitney, earths Crust, Lithosphere and Asthenosphere Crust and Lithosphere
2.
Pilbara
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The Pilbara is a large, dry, thinly populated region in the north of Western Australia. It is known for its Aboriginal peoples, its ancient landscapes and it is one of nine regions of the Regional Development Commissions Act 1993, and is also a bioregion under the Interim Biogeographic Regionalisation for Australia. The region has an population of 48,610 as of June 2010. The Pilbara covers an area of 502,000 km2, which some of Earths oldest rock formations. It includes landscapes of coastal plains and mountain ranges with cliffs, the major settlements of the region are Port Hedland, Karratha and Newman. The area is known for its petroleum, natural gas and iron ore deposits, other than mining, pastoral activities as well as fishing and tourism are the main industries. The Pilbara Aboriginal Language Centre Wangka Maya says that the name for the Pilbara region derives from the Aboriginal word bilybara, meaning dry in the Nyamal, alternatively, The Western Australia Gas Industry claims that the region takes its name from pilbarra, an Aboriginal word for the mullet. The Pilbara Creek is a tributary of the Yule River, a significant river in the region, pilbarra and barramundi can still be caught in the Yule River today. This Pilbara Creek lent its name to the Pilbara Goldfield, discovered in 1885, the first European to explore the area was Francis Thomas Gregory in 1861. Settlements along the coast at Cossack, Roebourne and Shellborough were established over ensuing decades as agricultural and pastoral centres,1900, these largely went into decline with the growth of other, more productive agricultural areas of the state. On 3 October 1952, the British conducted their first atomic bomb tests on the Montebello Islands as part of Operation Hurricane, the Aboriginal population of the Pilbara considerably predates, by 30-40,000 years, the European colonisation of the region. Archaeological evidence indicates people were living in the Pilbara even during the harsh climatic conditions of the Last Glacial Maximum. The early history of the first peoples is held within a tradition, archeological evidence. Near the town of Dampier is a known as Murujuga. Rock art in the Pilbara appears to have been etched into the hard rock surfaces. This does not preclude that painting was and is not performed in the Pilbara, in 2006, it was estimated that 15% of the population of the Pilbara was of Indigenous background, approximately 6,000 people. Family clans in the Pilbara who were supported by mining prospector, Don McLeod, developed skills for mining, for a short period money accumulated, which according to Aboriginal law was to be used for traditional ways. Eventually the funds were used to establish an independent Aboriginal-controlled school, the concept has expanded into a movement with around 20 similar schools established in northern Western Australia by the mid 1990s
3.
Western Australia
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Western Australia is a state occupying the entire western third of Australia. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Southern Ocean to the south, the state has about 2.6 million inhabitants, around 11% of the national total. 92% of the lives in the south-west corner of the state. The first European visitor to Western Australia was the Dutch explorer Dirk Hartog, the first European settlement of Western Australia occurred following the landing by Major Edmund Lockyer on 26 December 1826 of an expedition on behalf of the New South Wales colonial government. This was followed by the establishment of the Swan River Colony in 1829, including the site of the present-day capital, york was the first inland settlement in Western Australia. Situated 97 kilometres east of Perth, it was settled on 16 September 1831, Western Australia achieved responsible government in 1890, and federated with the other British colonies in Australia in 1901. Today its economy relies on mining, agriculture and tourism. The state produces 46% of Australias exports, Western Australia is the second-largest iron ore producer in the world. The International Hydrographic Organization designates the body of water south of the continent as part of the Indian Ocean, the total length of the states eastern border is 1,862 km. There are 20,781 km of coastline, including 7,892 km of island coastline, the total land area occupied by the state is 2.5 million km2. Most of the state is a low plateau with an elevation of about 400 metres, very low relief. This descends relatively sharply to the plains, in some cases forming a sharp escarpment. The extreme age of the landscape has meant that the soils are remarkably infertile, even soils derived from granitic bedrock contain an order of magnitude less available phosphorus and only half as much nitrogen as soils in comparable climates in other continents. Soils derived from extensive sandplains or ironstone are even less fertile, nearly devoid of soluble phosphate and also deficient in zinc, copper, molybdenum, the infertility of most of the soils has required heavy application by farmers of chemical fertilisers, particularly superphosphate, insecticides and herbicides. These have resulted in damage to invertebrate and bacterial populations, the grazing and use of hoofed mammals and, later, heavy machinery through the years have resulted in compaction of soils and great damage to the fragile soils. Large-scale land clearing for agriculture has damaged habitats for native flora, large areas of the states wheatbelt region have problems with dryland salinity and the loss of fresh water. The southwest coastal area has a Mediterranean climate and it was originally heavily forested, including large stands of karri, one of the tallest trees in the world. This agricultural region is one of the nine most bio-diverse terrestrial habitats, thanks to the offshore Leeuwin Current, the area is one of the top six regions for marine biodiversity and contains the most southerly coral reefs in the world
4.
Gigaannum
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days
5.
Kaapvaal Craton
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The Kaapvaal Craton, along with the Pilbara Craton of Western Australia, are the only remaining areas of pristine 3. 6–2.5 Ga crust on Earth. Similarities of rock records from both these cratons, especially of the overlying late Archean sequences, suggest that they were part of the Vaalbara supercontinent. The Kaapvaal Craton covers an area of approximately 1,200,000 km2 and is joined to the Zimbabwe Craton to the north by the Limpopo Belt. To the south and west, the Kaapvaal Craton is flanked by Proterozoic orogens, the craton is a mixture of early Archean granite greenstone terranes and older tonalitic gneisses, intruded by a variety of granitic plutons. This was then followed by extension and rifting when the Gaborone–Kanye. Early Archean crust is exposed only on the east side of the craton and comprises a collage of subdomains and crustal blocks characterised by distinctive igneous rocks. The belt is an east-northeast trending zone of granulite facies tectonites that separates the granitoid-greenstone terranes of the Kaapvaal and Zimbabwe cratons. The crustal evolution of the Limpopo Central Zone can be summarised into three periods,3. 2–2.9 Ga,2.6 Ga, and 2.0 Ga. The first two periods are characterised by magmatic activity leading to the formation of Archaean tonalite-trondhjemite-granodiorite such as the Sand River Gneisses, Early Proterozoic high-grade metamorphic conditions produced partial melting that formed large amounts of granitic melt. There is no indication that the Neoarchean to early Paleoproterozoic succession on the craton were sourced from the 2. 65–2.70 Ga orogenic event preserved in the Limpopo Metamorphic Complex. However, younger late-Paleoproterozoic red bed successions contain zircons of this interval as well as many ~2.0 Ga detrital zircons. Evidence of the layering and riverine erosion can be found throughout the Waterberg Massif within the Limpopo Central Zone. The Barberton greenstone belt, also known as the Makhonjwa Mountains, is situated on the edge of Kaapvaal Craton. It is well known for its gold mineralisation and for its komatiites, some of the oldest exposed rocks on Earth are located in the Barberton greenstone belt of the Swaziland–Barberton areas and these contain some of the oldest traces of life on earth. Only the rocks found in the Isua greenstone belt of Western Greenland are older, in April 2014, scientists reported finding evidence of the largest terrestrial meteor impact event to date near the Barberton Greenstone Belt. They estimated the impact occurred about 3.26 billion years ago, the crater from this event, if it still exists, has not yet been found. The Barberton greenstone belt consists of a sequence of mafic to ultramafic lavas, the GMS suite are found over large parts of the Kaapvaal Craton and their emplacement coincides with the first stabilisation of the central parts of the craton. The GMS suite in the Barberton granite-greenstone terrane shows very different internal and external characteristics from the earlier TTG suite, for the most part, the plutons appear undeformed
6.
South Africa
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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
7.
Vaalbara
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Vaalbara was an Archean supercontinent that consisted of the Kaapvaal craton, today located in eastern South Africa, and the Pilbara craton, today found in north-western Western Australia. Vaalbara was named by Cheney 1996 who derived the name from the last four letters of each cratons name, the two cratons are made of 3. 6±2.7 billion years old crust, making Vaalbara the oldest supercontinent on Earth. There has been some debate when and whether Vaalbara existed, an Archaean-Palaeoproterozoic link between South Africa and Western Australia was first proposed by Button 1976. He found a range of similarities between the Transvaal Basin in South Africa and the Hamersley Basin in Australia. Button, however, placed Madagascar between Africa and Australia and concluded that Gondwana must have had a long stable tectonic history and this model is supported by the palaeomagnetic data of Zegers, de Wit & White 1998. Reconstructions of the palaeolatitudes of the two cratons at 2. 78–2.77 Ga are ambiguous however, in the reconstruction of Wingate 1998 they fail to overlap, but they do in more recent reconstructions, for example Strik et al. Other scientists dispute the existence of Vaalbara and explain similarities between the two cratons as the product of global processes and they point to, for example, thick volcanic deposits on other cratons such as Amazonia, São Francisco, and Karnataka. Zimgarn, another proposed supercraton composed of the Zimbabwe and Yilgarn cratons at 2.41 Ga, is distinct from Vaalbara, zimgarn should have disintegrated around 2. 1–2.0 Ga to reassemble as the Kalahari and West Australian cratons around 1. 95–1.8 Ga. The Archaean-Palaeoproterozoic Grunehogna Craton in Dronning Maud Land, East Antarctica, Grunehogna collided with the rest of East Antarctica during the Mesoproterozoic assembly of the supercontinent Rodinia and the Grenville orogeny. The Neoproterozoic Pan-African orogeny and the assembly of Gondwana/Pannotia produced large shear zones between Grunehogna and Kalahari, during the Jurassic break-up of Gondwana these shear zones finally separated Grunehogna and the rest of Antarctica from Africa. Vaalbara thus remained stable for 1–0.4 Ga and hence had a life similar to that of later supercontinents such as Gondwana. Some palaeomagnetic reconstructions suggest a Palaeoarchaean Proto-Vaalbara is possible, although the existence of this 3. 6–3.2 Ga continent cant be unequivocally proven, South Africas Kaapvaal craton and Western Australias Pilbara craton have similar early Precambrian cover sequences. Kaapvaals Barberton granite-greenstone terrane and Pilbaras eastern block show evidence of four large meteorite impacts between 3.2 and 3.5 billion years ago, the high temperatures created by the impact’s force fused sediments into small glassy spherules. Spherules of 3.5 billion years old exist in South Africa and spherules of a similar age have been found in Western Australia, the spherules resemble the glassy chondrules in carbonaceous chondrites, which are found in carbon-rich meteorites and lunar soils. Remarkably similar lithostratigraphic and chronostratigraphic structural sequences between these two cratons have been noted for the period between 3.5 and 2.7 billion years ago. Paleomagnetic data from two ultramafic complexes in the cratons showed that at 3,870 million years the two cratons could have part of the same supercontinent. Both the Pilbara and Kaapvaal cratons show extensional faults which were active about 3,470 million years ago during felsic volcanism, the Pilbara and Kaapvaal cratons are some of the oldest rocks in the world and they contain well-preserved Archaean microfossils. A series of international drilling projects has revealed traces of microbial life, the oldest widely accepted evidence of photosynthesis by early life forms is molecular fossils found in 2.7 Ga-old shales in the Pilbara Craton
8.
Supercontinent
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In geology, a supercontinent is the assembly of most or all of Earths continental blocks or cratons to form a single large landmass. However, the definition of a supercontinent can be ambiguous, Many earth scientists, such as P. F. Hoffman, use the term supercontinent to mean a clustering of all continents. This definition leaves room for interpretation when labeling a continental body and is easier to apply to Precambrian times, the landmass of Pangaea is the collective name describing all of these continental masses when they were most recently in proximity to one another. This would classify Pangaea as a supercontinent, according to the definition by Rogers and Santosh, a supercontinent does not exist today. Supercontinents have assembled and dispersed multiple times in the geologic past, the positions of continents have been accurately determined back to the early Jurassic. However, beyond 200 Ma, continental positions are less certain. The following table displays historical supercontinents, using a general definition, there are two contrasting models for supercontinent evolution through geological time. The first model theorizes that at least two separate supercontinents existed comprising Vaalbara and Kenorland, the Neoarchean supercontinent consisted of Superia and Sclavia. These parts of Neoarchean age broke off at ~2300 and 2090 Ma, Nuna continued to develop during the Mesoproterozoic, primarily by lateral accretion of juvenile arcs, and in ~1000 Ma Nuna collided with other land masses, forming Rodinia. Between ~800 and 700 Ma Rodinia broke apart, however, before completely breaking up, some fragments of Rodinia had already come together to form Gondwana by ~530 Ma. Pangaea formed by ~300 Ma through the collision of Gondwana, Laurentia, Baltica, during the intervening periods, the poles conform to a unified apparent polar wander path. The explanation for the duration of the Protopangea-Paleopangea supercontinent appears to be that Lid Tectonics prevailed during Precambrian times. Plate Tectonics as seen on the contemporary Earth became dominant only during the part of geological times. The Phanerozoic supercontinent Pangaea began to break up 180 Ma and is doing so today. Because Pangaea is the most recent of Earths supercontinents, it is the most well known, contributing to Pangaeas popularity in the classroom is the fact that its reconstruction is almost as simple as fitting the present continents bordering the Atlantic-type oceans like puzzle pieces. A supercontinent cycle is the break-up of one supercontinent and the development of another, supercontinent cycles are not the same as the Wilson cycle, which is the opening and closing of an individual oceanic basin. The Wilson cycle rarely synchronizes with the timing of a supercontinent cycle, however, supercontinent cycles and Wilson cycles were both involved in the creation of Pangaea and Rodinia
