1.
Western Ghats
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Western Ghats மேற்கு தொடர்ச்சி மலை is a mountain range that runs parallel to the western coast of the Indian peninsula, located entirely in India. It is a UNESCO World Heritage Site and is one of the eight hottest hot-spots of biological diversity in the world and it is sometimes called the Great Escarpment of India. The range runs north to south along the edge of the Deccan Plateau. These hills cover 160,000 km2 and form the catchment area for complex riverine drainage systems that drain almost 40% of India, the Western Ghats block southwest monsoon winds from reaching the Deccan Plateau. The average elevation is around 1,200 m, at least 325 globally threatened species occur in the Western Ghats. The Western Ghats are the mountainous faulted and eroded edge of the Deccan Plateau, geologic evidence indicates that they were formed during the break-up of the supercontinent of Gondwana some 150 million years ago. Geophysical evidence indicates that the west coast of India came into being somewhere around 100 to 80 mya after it broke away from Madagascar, after the break-up, the western coast of India would have appeared as an abrupt cliff some 1,000 m in elevation. Basalt is the predominant rock found in the reaching a thickness of 3 km. Other rock types found are charnockites, granite gneiss, khondalites, leptynites, metamorphic gneisses with detached occurrences of limestone, iron ore. Residual laterite and bauxite ores are found in the southern hills. The Western Ghats extend from the Satpura Range in the north and it traverses south past the states of Maharashtra, Goa, Karnataka and Kerala. Major gaps in the range are the Goa Gap, between the Maharashtra and Karnataka sections, and the Palghat Gap on the Tamil Nadu and Kerala border between the Nilgiri Hills and the Anaimalai Hills. The mountains intercept the rain-bearing westerly monsoon winds, and are consequently an area of high rainfall, particularly on their western side. The northern portion of the coastal plain between the Western Ghats and the Arabian Sea is known as the Konkan, the central portion is called Kanara. The foothill region east of the Ghats in Maharashtra is known as Desh, the range is known as Sahyadri in Maharashtra and Karnataka. The Western Ghats meets the Eastern Ghats at Nilgiris in northwestern Tamil Nadu, Nilgiris connects Biligiriranga Hills in southeastern Karnataka with the Shevaroys and Tirumala hills. In the southern part of the range is Anamudi, the highest peak in Western Ghats, following is a list of some of the highest peaks of the Western Ghats, The Western Ghats form one of the four watersheds of India, feeding the perennial rivers of India. The major river systems originating in the Western Ghats include Godavari, Kaveri, Krishna, Thamiraparani, majority of streams draining the Western Ghats join these rivers and carry large volume of water during the monsoon months
2.
Matheran
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Matheran is a hill station and a municipal council in the Raigad district in the Indian state of Maharashtra. It is a station in Karjat Tahsil and is also the smallest hill station in India. It is located on the Western Ghats range at an elevation of around 800 m above sea level and it is located around 90 km from Mumbai, and 120 km from Pune. Matherans proximity to metropolitan cities makes it a popular weekend getaway for urban residents. Matheran, which means forest on the forehead is a region, declared by the Ministry of Environment, Forest and Climate Change. It is Asias only automobile-free hill station, There are around 38 designated look-out points in Matheran, including the Panorama Point that provides a 360 degree view of the surrounding area and also the Neral town. From this point, the view of sunset and sunrise is dramatic, the Louisa Point offers crystal clear view of the Prabal Fort. The other points are the One Tree Hill Point, Heart Point, Monkey Point, Porcupine Point, Rambagh Point, to stay there, there are plenty of hotels. There are a lot of Parsi bungalows. Beautiful old British-style architecture is preserved in Matheran, the roads are not metalled and are made of red laterite earth. There are many points in Matheran which give a view of the plains below. Matheran was identified by Hugh Poyntz Malet, the district collector of Thane district in May 1850. Lord Elphinstone, the then Governor of Bombay laid the foundations of the development as a hill station. The British developed Matheran as a resort to beat the summer heat in the region. Matheran is birthplace of freedom fighter Veer Bhai Kotwal. He was born on 1 December 1912 in a barber family, State Govt. has built a monument in his memory. The Matheran Hill Railway was built in 1907 by Sir Adamjee Peerbhoy and covers a distance of 20 km, over large swathes of forest territory. The Matheran hill railway, also known as Matheran Light Railway, was inspected by UNESCO world heritage site officials, indias other Hill Railways like the Darjeeling Railway, the Kangra Valley Railway, Nilgiri Mountain Railway are already on the list. Matheran has been declared an Eco-Sensitive zone by the Union Environment Ministry, a good collection of the dried plants is deposited in Blatter Herbarium, St. Xaviers College, Bombay, Mumbai
3.
Large igneous province
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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
4.
Deccan Plateau
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The Deccan Plateau is a large plateau in southern India. It rises to 100 metres in the north, and to more than 1 kilometre in the south and it extends over eight Indian states and encompasses a wide range of habitats, covering most of central and southern India. It is separated from the Gangetic plain to the north by the Satpura and Vindhya Ranges, the name Deccan is an anglicised form of the Prakrit word dakkhin, itself derived from the Sanskrit word dákṣiṇa, as the Deccan Plateau is located in southern part of Indian subcontinent. The Deccan region has historically lacked an enduring geo-political centre, and has been defined in various ways, geographers have attempted to define it using indices such as rainfall, vegetation, soil type or physical features. When considering physical features, it is taken to be the bounded by the Narmada River, the Eastern Ghats. The 16th century historian Firishta defined Deccan as the inhabited by the native speakers of Kannada, Marathi. Richard M. Eaton also settled on this linguistic definition, the Western Ghats mountain range is very tall and blocks the moisture from the southwest monsoon from reaching the Deccan Plateau, so the region receives very little rainfall. The eastern Deccan Plateau is at an elevation spanning the southeastern coast of India. Its forests are relatively dry but serve to retain the rain to form streams that feed into rivers that flow into basins. Most Deccan plateau rivers flow south, most of the central plateau is drained by the Tungabhadra River, Krishna River and its tributaries, including the Bhima River, which also run east. The climate of the region varies from semi-arid in the north to tropical in most of the region with distinct wet, rain falls during the monsoon season from about June to October. March to June can be dry and hot, with temperatures regularly exceeding 40 °C. The name derives from the Sanskrit daksina, the plateau is bounded on the east and west by the Ghats, while its northern extremity is the Vindhya Range. The Deccans average elevation is about 2,000 feet, sloping generally eastward, its rivers, the Godavari, Krishna. The plateaus climate is drier than that on the coasts and is arid in places, having once constituted a segment of the ancient continent of Gondwanaland, this land is the oldest and most stable in India. The average height of the Western Ghats, which run along the Arabian Sea, anaimudi Peak in Kerala, with a height of 2,695 m above sea level, is the highest peak of peninsular India. In the Nilgiris lie Ootacamund, the hill station of southern India. The western coastal plain is uneven and swift rivers flow through it that forms beautiful lagoons and backwaters, the east coast is wide with deltas formed by the rivers Godavari, Mahanadi and Kaveri
5.
India
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India, officially the Republic of India, is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and it is bounded by the Indian Ocean on the south, the Arabian Sea on the southwest, and the Bay of Bengal on the southeast. It shares land borders with Pakistan to the west, China, Nepal, and Bhutan to the northeast, in the Indian Ocean, India is in the vicinity of Sri Lanka and the Maldives. Indias Andaman and Nicobar Islands share a border with Thailand. The Indian subcontinent was home to the urban Indus Valley Civilisation of the 3rd millennium BCE, in the following millennium, the oldest scriptures associated with Hinduism began to be composed. Social stratification, based on caste, emerged in the first millennium BCE, early political consolidations took place under the Maurya and Gupta empires, the later peninsular Middle Kingdoms influenced cultures as far as southeast Asia. In the medieval era, Judaism, Zoroastrianism, Christianity, and Islam arrived, much of the north fell to the Delhi sultanate, the south was united under the Vijayanagara Empire. The economy expanded in the 17th century in the Mughal empire, in the mid-18th century, the subcontinent came under British East India Company rule, and in the mid-19th under British crown rule. A nationalist movement emerged in the late 19th century, which later, under Mahatma Gandhi, was noted for nonviolent resistance, in 2015, the Indian economy was the worlds seventh largest by nominal GDP and third largest by purchasing power parity. Following market-based economic reforms in 1991, India became one of the major economies and is considered a newly industrialised country. However, it continues to face the challenges of poverty, corruption, malnutrition, a nuclear weapons state and regional power, it has the third largest standing army in the world and ranks sixth in military expenditure among nations. India is a constitutional republic governed under a parliamentary system. It is a pluralistic, multilingual and multi-ethnic society and is home to a diversity of wildlife in a variety of protected habitats. The name India is derived from Indus, which originates from the Old Persian word Hindu, the latter term stems from the Sanskrit word Sindhu, which was the historical local appellation for the Indus River. The ancient Greeks referred to the Indians as Indoi, which translates as The people of the Indus, the geographical term Bharat, which is recognised by the Constitution of India as an official name for the country, is used by many Indian languages in its variations. Scholars believe it to be named after the Vedic tribe of Bharatas in the second millennium B. C. E and it is also traditionally associated with the rule of the legendary emperor Bharata. Gaṇarājya is the Sanskrit/Hindi term for republic dating back to the ancient times, hindustan is a Persian name for India dating back to the 3rd century B. C. E. It was introduced into India by the Mughals and widely used since then and its meaning varied, referring to a region that encompassed northern India and Pakistan or India in its entirety
6.
Volcano
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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, therefore, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
7.
Flood basalt
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A flood basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalt provinces such as the Deccan Traps of India are often called traps, rampino and Stothers cite eleven distinct flood basalt episodes occurring in the past 250 million years, creating large volcanic provinces, plateaus, and mountain ranges. However, more have been recognized such as the large Ontong Java Plateau, Large igneous provinces have been connected to five mass extinction events, and may be associated with bolide impacts. These have a low viscosity, which is why they flood rather than form taller volcanoes. Another explanation is that they result from the release, over a time period. The Deccan Traps of central India, the Siberian Traps, the Mesoproterozoic Mackenzie Large Igneous Province in Canada contains the Coppermine River flood basalts related to the Muskox layered intrusion. The maria on the Moon are additional, even more extensive, flood basalts on the ocean floor produce oceanic plateaus. The surface covered by one eruption can vary from around 200,000 km² to 1,500,000 km², the thickness can vary from 2000 metres to 12,000 m. These are smaller than the original due to erosion. Flood basalts have tholeiite and olivine compositions, the composition of the basalts from the Paraná is fairly typical of that of flood basalts, it contains phenocrysts occupying around 25% of the volume of rock in a fine-grained matrix. These phenocrysts are pyroxenes, plagioclases, opaque crystals such as titanium rich magnetite or ilmenite, sometimes more differentiated volcanic products such as andesites, dacites and rhyodacites have been observed, but only in small quantities at the top of former magma chambers. Subaerial flood basalts can be of two kinds, with a smooth or twisted surface, very compact surface, vesicles are rare, such lava flows may form underground rivers, when degassing fractures and conduits are present, very large flows may reach the surface. With a chaotic surface, the flood is very rich in bubbles of gas, with an irregular. In the Massif Central in Auvergne, France, there is an example of chaotic lava flow, produced by eruptions from Puy de la Vache. Geochemical analysis of the major oxides reveals a close to that of mid-ocean ridge basalts. These are in fact tholeiites with a silicon dioxide percentage close to 50% and it is this contamination that explains the difference between the two kinds of basalt mentioned above. The low phosphorus and titanium type has an excess of elements from the crust such as potassium and strontium, the content in incompatible elements of flood basalts is lower than that of ocean island basalts, but higher than that of mid-ocean ridge basalts. Basalt floods on the planet Venus are larger than those on Earth. S, magmatism at rift zones, The generation of volcanic continental margins and flood basalts
8.
Trap rock
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Trap rock, also known as either trapp or trap, is any dark-colored, fine-grained, non-granitic intrusive or extrusive igneous rock. Types of trap rock include basalt, peridotite, diabase, trapp is also used to refer to flood basalts, i. e. the Deccan Traps and Siberian Traps. The slow cooling of magma either as a sill or as a lava flow sometimes creates systematic vertical fractures within the resulting layer of trap rock. These fractures often form rock columns that are hexagonal. Trap rock, i. e. basalt or diabase, has a variety of uses, a major use for basalt is crushed rock for road and housing construction in concrete, macadam, and paving stones. It is also used for the production of cast rock that is used in corrosion and abrasion protection, as for sewage pipes and it was also used for foundations and railroad beds in the New Haven area. Well-known examples of outcropping trap rock include both intrusive sills and extrusive lava flows and they include the Palisades Sill, a Triassic,200 Ma diabase intrusion that forms the Palisade along 80 kilometers of the Hudson River in New York and New Jersey. Vast areas of rock in the form of thick lava flows and other volcanic rocks comprise the Deccan Traps of India. Devils Postpile National Monument Giants Causeway Organ Pipes National Park List of flood basalt provinces Siberian Traps Deccan Traps Emeishan Traps Viluy Traps
9.
Geology
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Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer generally to the study of the features of any terrestrial planet. Geology gives insight into the history of the Earth by providing the evidence for plate tectonics, the evolutionary history of life. Geology also plays a role in engineering and is a major academic discipline. The majority of data comes from research on solid Earth materials. These typically fall into one of two categories, rock and unconsolidated material, the majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three types of rock, igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between three types of rock, and magma. When a rock crystallizes from melt, it is an igneous rock, the sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism, all three types of rocks may be re-melted, when this happens, a new magma is formed, from which an igneous rock may once again crystallize. Geologists also study unlithified material which typically comes from more recent deposits and these materials are superficial deposits which lie above the bedrock. Because of this, the study of material is often known as Quaternary geology. This includes the study of sediment and soils, including studies in geomorphology, sedimentology and this theory is supported by several types of observations, including seafloor spreading, and the global distribution of mountain terrain and seismicity. This coupling between rigid plates moving on the surface of the Earth and the mantle is called plate tectonics. The development of plate tectonics provided a basis for many observations of the solid Earth. Long linear regions of geologic features could be explained as plate boundaries, mid-ocean ridges, high regions on the seafloor where hydrothermal vents and volcanoes exist, were explained as divergent boundaries, where two plates move apart. Arcs of volcanoes and earthquakes were explained as convergent boundaries, where one plate subducts under another, transform boundaries, such as the San Andreas Fault system, resulted in widespread powerful earthquakes. Plate tectonics also provided a mechanism for Alfred Wegeners theory of continental drift and they also provided a driving force for crustal deformation, and a new setting for the observations of structural geology
10.
Rock formation
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A rock formation is an isolated, scenic, or spectacular surface rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock, the term rock formation can also refer to specific sedimentary strata or other rock unit in stratigraphic and petrologic studies. Erosion later exposes them in their current form, an example is Bryce Canyon National Park in Utah. Metamorphic rocks are created by rocks that have transformed into another kind of rock, usually by some combination of heat, pressure. An example are the Seneca Rocks in West Virginia, igneous rocks are created when molten rock cools and solidifies, with or without crystallization. They may be either plutonic bodies or volcanic extrusives, again, erosive forces sculpt their current forms. An example is Half Dome in Yosemite National Park, geologists have created a number of terms to describe different rock structures in the landscape that can be formed by natural processes, Inselberg or monadnock is a residual relief feature. It can be a hill, a knob, ridge or small mountain that rises abruptly, like an island. Inselberg is a German word that means island mountain, uluru/Ayers Rock in Australia is a noted example. Peak Stack Mesa Butte Escarpment Gorge Sea cliff River cliff Stone run Crag Tor Promontory is a prominent mass of land which overlooks lower lying land or a body of water, here is a list of rock formations by continent
11.
Geologic time scale
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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
12.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
13.
Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
14.
Erosion
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In earth science, erosion is the action of surface processes that remove soil, rock, or dissolved material from one location on the Earths crust, then transport it away to another location. Eroded sediment or solutes may be transported just a few millimetres, the rates at which such processes act control how fast a surface is eroded. Feedbacks are also possible between rates of erosion and the amount of eroded material that is carried by, for example. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, while erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the rate of erosion in the region. Excessive erosion causes both on-site and off-site problems, on-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of bodies, as well as sediment-related damage to roads. Intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion, however, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, and the surface runoff which may result from rainfall, produces four types of soil erosion, splash erosion, sheet erosion, rill erosion. Splash erosion is generally seen as the first and least severe stage in the erosion process. In splash erosion, the impact of a falling raindrop creates a crater in the soil. The distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rate is greater than the rate at which water can infiltrate into the soil. If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope, sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes, generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres or less and this means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow
15.
Volcanic gas
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Volcanic gases include a variety of substances given off by active volcanoes. The sources of gases on Earth include, primordial and recycled constituents from the Earths mantle, assimilated constituents from the Earths crust, groundwater. Substances that may become gaseous or give off gases when heated are termed volatile substances. The principal components of volcanic gases are water vapor, carbon dioxide, sulfur either as sulfur dioxide or hydrogen sulfide, nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen. Other compounds detected in volcanic gases are oxygen, hydrogen chloride, hydrogen fluoride, hydrogen bromide, nitrogen oxide, sulfur hexafluoride, carbonyl sulfide, exotic trace compounds include mercury, halocarbons, and halogen oxide radicals. The abundance of gases varies considerably from volcano to volcano, water vapor is consistently the most common volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions, volcanoes located at convergent plate boundaries emit more water vapor and chlorine than volcanoes at hot spots or divergent plate boundaries. This is caused by the addition of seawater into magmas formed at subduction zones, convergent plate boundary volcanoes also have higher H2O/H2, H2O/CO2, CO2/He and N2/He ratios than hot spot or divergent plate boundary volcanoes. Magma contains dissolved volatile components, as described above, the solubilities of the different volatile constituents are dependent on pressure, temperature and the composition of the magma. As magma ascends towards the surface, the ambient pressure decreases, once the solubility decreases below the volatile concentration, the volatiles will tend to come out of solution within the magma and form a separate gas phase. The gas will initially be distributed throughout the magma as small bubbles, as the magma ascends the bubbles grow through a combination of expansion through decompression and growth as the solubility of volatiles in the magma decreases further causing more gas to exsolve. In the former case, the bubbles may rise through the magma and accumulate at a vertical surface, in volcanoes with an open path to the surface, e. g. Stromboli in Italy, the bubbles may reach the surface and as they pop small explosions occur. In the latter case, the gas can flow rapidly through the continuous permeable network towards the surface and this mechanism has been used to explain activity at Santiaguito, Santa Maria volcano, Guatemala and Soufrière Hills Volcano, Montserrat. If the gas cannot escape fast enough from the magma, it will fragment the magma into small particles of ash, the fluidised ash has a much lower resistance to motion than the viscous magma, so accelerates, causing further expansion of the gases and acceleration of the mixture. This sequence of events drives explosive volcanism, whether gas can escape gently or not is determined by the total volatile contents of the initial magma and the viscosity of the magma, which is controlled by its composition. The term closed system degassing refers to the case where gas and its parent magma ascend together, the composition of the emitted gas is in equilibrium with the composition of the magma at the pressure, temperature where the gas leaves the system. In open system degassing, the gas leaves its parent magma, the gas released at the surface has a composition that is a mass-flow average of the magma exsolved at various depths and is not representative of the magma conditions at any one depth. Molten rock near the atmosphere releases high-temperature volcanic gas, in explosive volcanic eruptions, sudden release of gases from magma may cause rapid movements of the molten rock
16.
Climate change
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Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time. Climate change may refer to a change in weather conditions. Climate change is caused by such as biotic processes, variations in solar radiation received by Earth, plate tectonics. Certain human activities have also identified as significant causes of recent climate change. Scientists actively work to understand past and future climate by using observations, more recent data are provided by the instrumental record. The most general definition of change is a change in the statistical properties of the climate system when considered over long periods of time. Accordingly, fluctuations over periods shorter than a few decades, such as El Niño, the term climate change is often used to refer specifically to anthropogenic climate change. Anthropogenic climate change is caused by activity, as opposed to changes in climate that may have resulted as part of Earths natural processes. In this sense, especially in the context of environmental policy, within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse gas levels affect. A related term is climatic change, in 1966, the World Meteorological Organization proposed the term climatic change to encompass all forms of climatic variability on time-scales longer than 10 years, regardless of cause. Change was a given and climatic was used as an adjective to describe this kind of change, when it was realized that human activities had a potential to drastically alter the climate, the term climate change replaced climatic change as the dominant term to reflect an anthropogenic cause. Climate change was incorporated in the title of the Intergovernmental Panel on Climate Change, Climate change, used as a noun, became an issue rather than the technical description of changing weather. On the broadest scale, the rate at which energy is received from the Sun and this energy is distributed around the globe by winds, ocean currents, and other mechanisms to affect the climates of different regions. Factors that can shape climate are called climate forcings or forcing mechanisms, there are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the system, such as the oceans and ice caps, respond more slowly in reaction to climate forcings. There are also key factors which when exceeded can produce rapid change. Forcing mechanisms can be internal or external. Internal forcing mechanisms are natural processes within the system itself
17.
Chicxulub crater
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The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named and it was formed by a large asteroid or comet about 10 kilometres in diameter, the Chicxulub impactor, striking the Earth. The crater is more than 180 kilometers in diameter and 20 km in depth and it makes the feature the third of the largest confirmed impact structures on Earth. The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán during the late 1970s, Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature, evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. Penfields job was to use data to scout possible locations for oil drilling. In the data, Penfield found a huge underwater arc with extraordinary symmetry in a ring 70 km across and he then obtained a gravity map of the Yucatán made in the 1960s. A decade earlier, the same map suggested a feature to contractor Robert Baltosser. Penfield found another arc on the peninsula itself, the ends of which pointed northward, Pemex disallowed release of specific data but let Penfield and company official Antonio Camargo present their results at the 1981 Society of Exploration Geophysicists conference. That years conference was underattended and their report attracted scant attention, coincidentally, many experts in impact craters and the K–Pg boundary were attending a separate conference on Earth impacts. Although Penfield had plenty of data sets, he had no rock cores or other physical evidence of an impact. He knew Pemex had drilled exploratory wells in the region, in 1951, one bored into what was described as a thick layer of andesite about 1.3 kilometres down. This layer could have resulted from the heat and pressure of an Earth impact. Penfield tried to secure site samples, but was told such samples had been lost or destroyed, when attempts at returning to the drill sites and looking for rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work. At the same time, in 1980, geologist Walter Alvarez and his father, Nobel Prize-winning scientist Luis Walter Alvarez and their evidence included greenish-brown clay with surplus iridium containing shocked quartz grains and small weathered glass beads that looked to be tektites. Thick, jumbled deposits of rock fragments were also present, thought to have been scoured from one place. Such deposits occur in locations but seem concentrated in the Caribbean basin at the K–Pg boundary. So when Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield nuclear detonations
18.
Impact winter
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An impact winter is a hypothesized period of prolonged cold weather due to the impact of a large asteroid or comet on the Earths surface. If an asteroid were to land or a shallow body of water, it would eject an enormous amount of dust, ash. This would cause the temperature to decrease drastically. It has been proposed that an impact winter could lead to mass extinction, each year, the Earth is hit by 5 m diameter meteoroids that deliver an explosion 50 km above the surface with the power equivalent of one kiloton TNT. The Earth is hit every day by a less than 5 m in diameter. The meteors that do make it to the surface tend to strike unpopulated areas, and cause no harm. A human is likely to die in a fire, flood, or other natural disaster than to die because of an asteroid or comet impact. Another study in 1994 found a 1 in 10,000 chance that the Earth will be hit by an asteroid or comet with a diameter of about 2 km during the next century. This object would be capable of disrupting the ecosphere and would kill a fraction of the worlds population. One such object, Asteroid 1950 DA, currently has a 0. 005% chance of colliding with Earth in the year 2880, the probability goes down as orbits are refined with additional measurements. This could happen for long period comets also but the chance is highest for short period comets, the chance of these directly impacting Earth is far lower than an NEO impact. The Earth experiences a never ending barrage of cosmic debris, small particles burn up as they enter the atmosphere and are visible as meteors. Many of them go unnoticed by the person even though not all of them burn up before they hit the Earths surface. Those that strike the surface are known as meteorites, so clearly not every object that hits the Earth will cause an extinction level event or even cause any real harm. Objects release most of their energy in the atmosphere and will explode if they experience a column of atmosphere greater than or equal to their mass. Extinction sized impacts on the Earth occur about every 100 million years, although extinction events happen very rarely, large projectiles can do severe damage. This section will discuss the nature of the hazards posed by projectiles as a function of their size, a large asteroid or comet could collide with the Earths surface with the force of hundreds to thousands of times the force of all the nuclear bombs on the Earth. For example, the K/T boundary impact has been proposed to have caused extinction of all non-avian dinosaurs 66 million years ago, early estimates of this asteroids size put it at about 10 km in diameter
19.
Zeolite
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Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts. Based on this, he called the material zeolite, from the Greek ζέω, meaning to boil and λίθος, the classic reference for the field has been Zeolite molecular sieves, structure, chemistry, and use by Donald W. Breck. Zeolites occur naturally but are produced industrially on a large scale. As of September 2016,232 unique zeolite frameworks have been identified, every new zeolite structure that is obtained has to be approved by the International Zeolite Association Structure Commission and receives a three letter designation. Zeolites have a structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution, some of the more common mineral zeolites are analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, and stilbite. An example of the formula of a zeolite is, Na2Al2Si3O10·2H2O. Natural zeolites form where volcanic rocks and ash layers react with alkaline groundwater, Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, quartz, for this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential. Zeolites are the members of the family of microporous solids known as molecular sieves mainly consisting of Si, Al, O, and metals including Ti, Sn, Zn. The term molecular sieve refers to a property of these materials. This is due to a very regular structure of molecular dimensions. The maximum size of the molecular or ionic species that can enter the pores of a zeolite is controlled by the dimensions of the channels, therefore, the pores in many zeolites are not cylindrical. Zeolites transform to other minerals under weathering, hydrothermal alteration or metamorphic conditions, the sequence of silica-poor volcanic rocks commonly progresses from, Cowlesite → levyne–offretite → analcime → thomsonite–mesolite-scolecite → chabazite → calcite. Industrially important zeolites are produced synthetically, typical procedures entail heating aqueous solutions of alumina and silica with sodium hydroxide. Equivalent reagents include sodium aluminate and sodium silicate, further variations include changes in the cations to include quaternary ammonium cations. Synthetic zeolites hold some key advantages over their natural analogues, the synthetic materials are manufactured in a uniform, phase-pure state. It is also possible to produce zeolite structures that do not appear in nature, Zeolite A is a well-known example
20.
Calcite
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Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of hardness, based on scratch hardness comparison. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite, aragonite will change to calcite at 380–470 °C, and vaterite is even less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime and it is thus etymologically related to chalk. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals, however, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms and it may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form and its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a gravity of 2.71. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes, acute scalenohedral crystals are sometimes referred to as dogtooth spar while the rhombohedral form is sometimes referred to as nailhead spar. Single calcite crystals display an optical property called birefringence and this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669, at a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in water, acidity can cause dissolution of calcite. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite, calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, high-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry
21.
Vug
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A vug, vugh, or vugg is a small to medium-sized cavity inside rock. It may be formed through a variety of processes, most commonly, cracks and fissures opened by tectonic activity are partially filled by quartz, calcite, and other secondary minerals. Open spaces within ancient collapse breccias are another important source of vugs, vugs may also form when mineral crystals or fossils inside a rock matrix are later removed through erosion or dissolution processes, leaving behind irregular voids. The inner surfaces of such vugs are often coated with a crystal druse, fine crystals are often found in vugs where the open space allows the free development of external crystal form. The term vug is not applied to veins and fissures that have completely filled. Geodes are a common vug-formed rock, although that term is reserved for more rounded crystal-lined cavities in sedimentary rocks. The word vug was introduced to the English language by Cornish miners, the Cornish word was vooga, which meant cave. Vesicular texture Rock microstructure Amygdule The dictionary definition of vug at Wiktionary
22.
Tholeiitic magma series
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The tholeiitic magma series, named after the German municipality of Tholey, is one of two main magma series in igneous rocks, the other magma series being the calc-alkaline. A magma series is a series of compositions that describes the evolution of a mafic magma, the International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to the term tholeiite. Rocks in the tholeiitic magma series are classified as subalkaline and are distinguished from rocks in the calc-alkaline magma series by the state of the magma they crystallized from. The difference between these two series can be seen on an AFM diagram, a ternary diagram showing the relative proportions of the oxides Na2O + K2O, FeO + Fe2O3. As magmas cool, they precipitate out significantly more iron and magnesium than alkali, like all basalt, the rock type is dominated by clinopyroxene plus plagioclase, with minor iron-titanium oxides. Orthopyroxene or pigeonite may also be present in tholeiitic basalt, and olivine, if present, tridymite or quartz may be present in the fine-grained groundmass of tholeiitic basalt, and feldspathoids are absent. Tholeiitic rocks may have a fine, glassy groundmass, as may other types of basalt, basalt magmas are partial melts of peridotite produced by decompression melting in the Earths mantle, a process described for igneous rocks. Tholeiitic basalts are the most common volcanic rocks on Earth, as they are produced by submarine volcanism at mid-ocean ridges, MORB, the acronym for typical mid-ocean-ridge basalt, is a type of tholeiitic basalt particularly low in incompatible elements. In contrast, alkali basalt is not typical at ocean ridges, because the Moon is extremely reduced, all of its basalt is tholeiitic. Petrology Igneous differentiation R. W. Le Maitre, A. Streckeisen, zanettin, M. J. Le Bas, B
23.
Nephelinite
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Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene. If olivine is present, the rock may be classified as an olivine nephelinite, nephelinite is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene and calcic plagioclase, basalt, alkali basalt, basanite, tephritic nephelinite, and nephelinite differ partly in the relative proportions of plagioclase and nepheline. Alkali basalt may contain minor nepheline and does contain nepheline in its CIPW normative mineralogy, a critical ratio in the classification of these rocks is the ratio nepheline/. Basanite has a value of this ratio between 0.1 and 0.6 and also more than 10% olivine. Tephritic nephelinite has a value between 0.6 and 0.9, nephelinite has a value greater than 0.9. Le Maitre defines and discusses these and other criteria in the classification of igneous rocks, nephelinite is an example of a silica-undersaturated igneous rock. Silica-undersaturated mafic igneous rocks contain magnesian olivine but not magnesian orthopyroxene, silica-saturated igneous rocks fall in between these two classes. Silica-undersaturated, mafic rocks are much less abundant than silica-saturated and oversaturated basalts. Nephelinites are also associated with carbonatite in some occurrences, consistent with source rocks relatively rich in carbon dioxide, nephelinite is found on ocean islands such as Oahu, although the rock type is very rare in the Hawaiian islands. It is found in a variety of continental settings, an example is the Hamada nephelinite lava flow in southwest Japan which occurred in the late Miocene age. Nephelinite is also associated with the highly alkalic volcanism of the Ol Doinyo Lengai volcanic field in Tanzania, Nyiragongo, another African volcano known for its semipermanent lava lake activity, erupts lava made of melilite nephelinite. The unusual chemical makeup of this igneous rock may be a factor in the fluidity of its lavas. Olivine nephelinite flows also occur in the Wells Gray-Clearwater volcanic field in east-central British Columbia, melilite olivine nephelinite intrusives of Cretaceous age are found in the area around Uvalde, Texas. Roger W. Le Maitre, Igneous Rocks, A Classification, ISBN 0-521-66215-X Hamada nephelinite, SW Japan Oldoinyo Lengai volcano, Eastern Rift Valley, North Tanzania Demant, A. Lestrade, P. Lubala, R. T. Kampunzu, A. B. Durieux, J. Volcanological and petrological evolution of Nyiragongo volcano, Virunga volcanic field, daniel P. Miggins, Charles D. Blome, and David V. Smith. Preliminary Argon40/Argon39 geochronology of igneous intrusions from Uvalde County, Texas, U. S. Geological Survey Open-File Report 2004-1031. In usgs. gov Chisholm, Hugh, ed. nephelinites, nefelinita in - Atlas de rocas ígneas
24.
Lamprophyre
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Lamprophyres are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions. They are alkaline silica-undersaturated mafic or ultramafic rocks with high magnesium oxide, >3% potassium oxide, high sodium oxide and high nickel, lamprophyres occur throughout all geologic eras. Archaean examples are commonly associated with gold deposits. Cenozoic examples include magnesian rocks in Mexico and South America, modern science treats lamprophyres as a catch-all term for ultrapotassic mafic igneous rocks which have primary mineralogy consisting of amphibole or biotite, and with feldspar in the groundmass. They are classified under the IUGS Nomenclature for Igneous Rocks separately, for example, the TAS scheme is inappropriate due to the control of mineralogy by potassium, not by calcium or sodium. Classification schemes which include information, may be required to properly describe lamprophyres. Rock considered lamprophyres are part of a clan of rocks, with similar mineralogy, textures, lamprophyres are similar to lamproites and kimberlites. While modern concepts see orangeites, lamproites and kimberlites as separate, Mitchell considered the lamprophyres as a facies of igneous rocks created by a set of conditions. Either scheme may apply to some, but not all, occurrences and variations of the group of rocks known as lamprophyres. Rock considered lamprophyres to be derived from deep, volatile-driven melting in a subduction zone setting, others such as Mitchell consider them to be late offshoots of plutons, etc. though this can be difficult to reconcile with their primitive melt chemistry and mineralogy. Lamprophyres are a group of rocks containing phenocrysts, usually of biotite and amphibole, and pyroxene and they are thus distinguished from the porphyries and porphyrites in which the feldspar has crystallized in two generations. They are essentially dike rocks, occurring as dikes and thin sills and they are usually dark in color, owing to the abundance of ferro-magnesian silicates, of high specific gravity and liable to decomposition. For these reasons they have defined as a melanocrate series. Biotite and amphibole are panidiomorphic, all are euhedral, well formed, feldspar is restricted to the ground mass. In many lamprophyres the pale quartz and felspathic ingredients tend to occur in rounded spots, or ocelli and these spots may consist of radiate or brush-like feldspars or of quartz and feldspar. A central area of quartz or of analcite probably represents an original miarolitic cavity infilled at a later period, the presence or absence of the four dominant minerals, orthoclase, plagioclase, biotite and hornblende, determines the species, Minette contains biotite and orthoclase. Each variety of lamprophyre may and often contain all four minerals but is named according to the two which predominate. These rocks contain iron oxides, apatite, sometimes sphene, augite
25.
Carbonatite
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Carbonatite is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification, carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. They are, almost exclusively, associated with continental rift-related tectonic settings and it seems that there has been a steady increase in the carbonatitic igneous activity through the earths history, from the Archean Eon to the present. Nearly all carbonatite occurrences are intrusives or subvolcanic intrusives and this is because carbonatite lava flows, being composed largely of soluble carbonates, are easily weathered and are therefore unlikely to be preserved in the geologic record. Carbonatite eruptions as lava may therefore not be as uncommon as thought, only one carbonatite volcano is known to have erupted in historical time, the active Ol Doinyo Lengai volcano in Tanzania. It erupts with the lowest temperature lava in the world, at 500-600 °C, the lava is natrocarbonatite dominated by nyerereite and gregoryite. Carbonatites are rare, peculiar rocks formed by unusual processes. Historically, carbonatites were thought to form by melting of limestone or marble by intrusion of magma, for example, the carbon isotopic composition of carbonatites is mantle-like and not like sedimentary limestone. Recognition of carbonatites may be difficult, especially as their mineralogy and they may also be sources of mica or vermiculite. Carbonatites are classed as calcitic sovite and alvikite varieties or facies, the two are also distinguished by minor and trace element composition. The terms rauhaugite and beforsite refer to dolomite- and ankerite-rich occurrences, examples with 50 - 70% carbonate minerals are termed silico-carbonatites. Additionally carbonatites may be enriched in magnetite and apatite or rare earth elements, fluorine. Natrocarbonatite is made up largely of two minerals, nyerereite and gregoryite and these minerals are both carbonates in which sodium and potassium are present in significant quantities. Both are anhydrous and when they come into contact with the moisture in the atmosphere, the black or dark brown lava and ash erupted begins to turn white within a few hours. Most carbonatites tend to include some silicate mineral fraction, by definition an igneous rock containing carbonate minerals is classified as a carbonatite. Silicate minerals associated with such compositions are pyroxene, olivine, and silica-undersaturated minerals such as nepheline, geochemically, carbonatites are dominated by incompatible elements and depletions in compatible elements. This together with their silica-undersaturated composition supports inferences that carbonatites are formed by low degrees of partial melting, a specific type of hydrothermal alteration termed fenitization is typically associated with carbonatite intrusions. This alteration assemblage produces a unique rock mineralogy termed a fenite after its type locality, the alteration consists of metasomatic halos consisting of sodium rich silicates arfvedsonite, barkevikite and glaucophane along with phosphates, hematite and other iron and titanium oxides
26.
Xenolith
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A xenolith is a rock fragment which becomes enveloped in a larger rock during the latters development and solidification. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement, a xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes, although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in sedimentary rock. Xenoliths are sometimes found in recovered meteorites, xenoliths and xenocrysts provide important information about the composition of the otherwise inaccessible mantle. Basalts, kimberlites, lamproites and lamprophyres, which have their source in the mantle, often contain fragments. Xenoliths of dunite, peridotite and spinel lherzolite in basaltic lava flows are one example, kimberlites contain, in addition to diamond xenocrysts, fragments of lherzolites of varying composition. The aluminium-bearing minerals of these fragments provide clues to the depth of origin, calcic plagioclase is stable to a depth of 25 km. Between 25 km and about 60 km, spinel is the stable aluminium phase, at depths greater than about 60 km, dense garnet becomes the aluminium-bearing mineral. Some kimberlites contain xenoliths of eclogite, which is considered to be the high-pressure metamorphic product of basaltic oceanic crust, the large-scale inclusion of foreign rock strata at the margins of an igneous intrusion is called a roof pendant. Blatt, Harvey, and Robert J. Tracy
27.
Kutch district
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Kutch district is a district of Gujarat state in western India. Covering an area of 45,674 km², it is the largest district of India, the population of Kutch is 2,092,371. It has 10 Talukas,939 villages and 6 Municipalities, the same word is also used in Sanskrit origin for a tortoise. The Rann is famous for its salt flats which become snow white after the shallow water dries up each season before the monsoon rains. The district is famous for ecologically important Banni grasslands with their seasonal marshy wetlands which form the outer belt of the Rann of Kutch. Kutch District is surrounded by the Gulf of Kutch and the Arabian Sea in south and west, while northern and eastern parts are surrounded by the Great and Little Rann of Kutch. When there were not many dams built on its rivers, the Rann of Kutch remained wetlands for a part of the year. Even today, the region remains wet for a significant part of year, the district had a population of 2,092,371 as of 2011 census, of which 30% were urban. Motor vehicles registered in Kutch district have their registration Number starting with GJ-12, the district is well connected by road, rail and air. There are four airports in the district, Naliya, Kandla, Mundra, Bhuj is well connected with Mumbai airport. Being a border district, Kutch has both an army and an airforce base, the history of Kutch can be traced back to prehistorical times. There are several related to Indus valley civilization in region and is mentioned in Hindu mythology. In historical times, Kutch is mentioned in Greek writings during Alexander, by fifth century, Maitraka of Valabhi took over from which its close association with ruling clans of Gujarat started. Chavdas ruled the eastern and central parts by seventh century but were came under Chaulukyas by tenth century, after fall of Chaulukya, Vaghelas ruled the state. Following conquest of Sindh by Muslim rulers, Rajput Samma started moving southwards to Kutch, by tenth century, they controlled significant area of Kutch and by thirteenth century they controlled whole of Kutch and adopted a new dynastic identity, Jadeja. For three centuries, Kutch was divided and ruled by three different branches of Jadeja brothers. One of his descendants, Rayadhan II left three sons of two died and third son, Pragmalji I took over the state and founded the current lineage of rulers at the start of the seventeenth century. The decedents of other brothers founded states in Kathiawar, the state accepted suzerainty of British East India Company in 1819 when Kutch was defeated in battle
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Eocene
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The Eocene Epoch, lasting from 56 to 33.9 million years ago, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. As with other periods, the strata that define the start and end of the epoch are well identified. The name Eocene comes from the Ancient Greek ἠώς and καινός, the Eocene epoch is conventionally divided into early, middle, and late subdivisions. The corresponding rocks are referred to as lower, middle, the Ypresian stage constitutes the lower, the Priabonian stage the upper, and the Lutetian and Bartonian stages are united as the middle Eocene. The Eocene Epoch contained a variety of different climate conditions that includes the warmest climate in the Cenozoic Era. During this period of time, little to no ice was present on Earth with a difference in temperature from the equator to the poles. Following the maximum was a descent into an icehouse climate from the Eocene Optimum to the Eocene-Oligocene transition at 34 million years ago. During this decrease ice began to reappear at the poles, greenhouse gases, in particular carbon dioxide and methane, played a significant role during the Eocene in controlling the surface temperature. For the early Eocene there is discussion on how much carbon dioxide was in the atmosphere. This is due to numerous proxies representing different atmospheric carbon dioxide content, for contrast, today the carbon dioxide levels are at 400 ppm or 0. 04%. At about the beginning of the Eocene Epoch the amount of oxygen in the atmosphere more or less doubled. During the early Eocene, methane was another gas that had a drastic effect on the climate. In comparison to carbon dioxide, methane has much effect on temperature as methane is ~34 times more effective per molecule than carbon dioxide on a 100-year scale. Most of the methane released to the atmosphere during this period of time would have been from wetlands, swamps, the atmospheric methane concentration today is 0. 000179% or 1.79 ppmv. Due to the climate and sea level rise associated with the early Eocene, more wetlands, more forests. Comparing the early Eocene production of methane to current levels of atmospheric methane, biogenic production of methane produces carbon dioxide and water vapor along with the methane, as well as yielding infrared radiation
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Mantle plume
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A mantle plume is a mechanism proposed in 1971 to explain volcanic regions of the Earth that were not thought to be explicable by the then-new theory of plate tectonics. Some such volcanic regions lie far from plate boundaries, for example. Others represent unusually large-volume volcanism, whether on plate boundaries, e. g. Iceland, a mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earths mantle becoming a diapir in the Earths crust. The currently active volcanic centers are known as hot spots, the hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes, another hypothesis for unusual volcanic regions is the Plate model. In 1971, geophysicist W. Jason Morgan proposed the hypothesis of mantle plumes, in this hypothesis, convection in the mantle transports heat from the core to the Earths surface in thermal diapirs. The latter type of convection is postulated to be independent of plate motions, the sizes and occurrence of mushroom mantle plumes can be predicted easily by transient instability theory developed by Tan and Thorpe. The theory predicts mushroom mantle plumes of about 2000 km diameter with a time of about 830 Myr for a core mantle heat flux of 20 mW/m2. The number of mantle plumes is predicted to be about 17, the plume hypothesis was studied using laboratory experiments conducted in small fluid-filled tanks in the early 1970s. Thermal or compositional fluid-dynamical plumes produced in that way were presented as models for the much larger postulated mantle plumes, the entire structure is considered to resemble a mushroom. The bulbous head of thermal plumes forms because hot material moves upward through the faster than the plume itself rises through its surroundings. In the late 1980s and early 1990s, experiments with thermal models showed that as the bulbous head expands it may entrain some of the adjacent mantle into the head. When a plume head encounters the base of the lithosphere, it is expected to flatten out against this barrier and it may then erupt onto the surface. Numerical modelling predicts that melting and eruption will take place several million years. These eruptions have been linked to flood basalts, although many of those erupt over much shorter time scales, flood basalts in the oceans are known as oceanic plateaus, and include the Ontong Java plateau of the western Pacific Ocean and the Kerguelen Plateau of the Indian Ocean. As the overlying tectonic plate moves over this hot spot, the eruption of magma from the fixed conduit onto the surface is expected to form a chain of volcanoes that parallels plate motion, the Hawaiian Islands chain in the Pacific Ocean is the type example. The eruption of continental flood basalts is often associated with continental rifting and this has led to the hypothesis that mantle plumes contribute to continental rifting and the formation of ocean basins. In the context of the alternative Plate model, continental breakup is an integral to plate tectonics
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Hotspot (geology)
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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
31.
Rift
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In geology, a rift is a linear zone where the Earths crust and lithosphere are being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting, where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the area may contain volcanic rocks, and active volcanism is a part of many. Major rifts occur along the axis of most mid-ocean ridges. Failed rifts are the result of rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a junction where three converging rifts meet over a hotspot. Two of these evolve to the point of spreading, while the third ultimately fails. Most rifts consist of a series of segments that together form the linear zone characteristic of rifts. The individual rift segments have a dominantly half-graben geometry, controlled by a single basin-bounding fault, segment lengths vary between rifts, depending on the elastic thickness of the lithosphere. Areas of thick colder lithosphere, such as the Baikal Rift have segment lengths in excess of 80 km, while in areas of warmer thin lithosphere, segment lengths may be less than 30 km. Along the axis of the rift the position, and in cases the polarity. Segment boundaries often have a complex structure and generally cross the rift axis at a high angle. These segment boundary zones accommodate the differences in fault displacement between the segments and are known as accommodation zones. Accommodation zones may be located where older crustal structures intersect the rift axis, in the Gulf of Suez rift, the Zaafarana accommodation zone is located where a shear zone in the Arabian-Nubian Shield meets the rift. At the onset of rifting, the part of the lithosphere starts to extend on a series of initially unconnected normal faults. In subaerial rifts, drainage at this stage is generally internal, as the rift evolves, some of the individual fault segments grow, eventually becoming linked together to form the larger bounding faults. Subsequent extension becomes concentrated on these faults, the longer faults and wider fault spacing leads to more continuous areas of fault-related subsidence along the rift axis. Significant uplift of the rift shoulders develops at this stage, strongly influencing drainage, during rifting, as the crust is thinned, the Earths surface subsides and the Moho becomes correspondingly raised
32.
Mascarene Plateau
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The Mascarene Plateau is a submarine plateau in the Indian Ocean, north and east of Madagascar. The plateau extends approximately 2,000 km, from the Seychelles in the north to Réunion in the south. The plateau covers an area of over 115,000 km2 of shallow water, with depths ranging from 8–150 m and it is the second largest undersea plateau in the Indian Ocean after the Kerguelen Plateau. The northern part of the Mascarene plateau includes the Seychelles and Agaléga Islands, the southern part of the Mascarene plateau includes the Mascarene Islands, Saya de Malha Bank, Nazareth Bank, Soudan Banks, and Hawkins Bank. The Mascarene Islands are the islands of Mauritius, Réunion, Rodrigues. The northern part of the Mascarene plateau is formed of granite, the granite is topped with deposits of limestone and basalt. The basalt deposits in the Seychelles are from the Deccan Traps eruption, the southern part of the Mascarene plateau, also known as Southern Mascarene plateau, was formed by the Réunion volcanic hotspot along with the Chagos-Laccadive Ridge. The Saya de Malha Bank formed 35 million years ago, and the Nazareth Bank, limestone banks found on the plateau are the remnants of coral reefs, indicating that the plateau was once a succession of islands. Some of the banks may have been islands as recently as 18,000 –6,000 years ago, Mauritius formed 8 –10 million years ago, and Rodrigues and Réunion formed around two million years ago. Piton de la Fournaise volcano on Réunion is one of the most active volcanoes in the world, Seychelles Plate Mauritia Geography of Seychelles Volume 115 Scientific Results. Proceedings of the Ocean Drilling Program
33.
Seafloor spreading
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Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics, basaltic magma rises up the fractures and cools on the ocean floor to form new seabed. Older rocks will be farther away from the spreading zone while younger rocks will be found nearer to the spreading zone. Additionally spreading rates determine if the ridge is a fast, intermediate, as a general rule, fast ridges see spreading rate of more than 9 cm/year. Intermediate ridges have a rate of 4-9 cm/year while slow spreading ridges have a rate less than 4 cm/year. Earlier theories of continental drift were that continents ploughed through the sea, the idea that the seafloor itself moves as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s. The theory is accepted now, and the phenomenon is known to be caused by convection currents in the asthenosphere, which is ductile, or plastic. In the general case, sea floor spreading starts as a rift in a land mass. The process starts with heating at the base of the continental crust which causes it to become more plastic, because less dense objects rise in relation to denser objects, the area being heated becomes a broad dome. As the crust bows upward, fractures occur that gradually grow into rifts, the typical rift system consists of three rift arms at approximately 120 degree angles. These areas are named triple junctions and can be found in places across the world today. The separated margins of the continents evolve to form passive margins, Hess theory was that new seafloor is formed when magma is forced upward toward the surface at a mid-ocean ridge. If spreading continues past the incipient stage described above, two of the arms will open while the third arm stops opening and becomes a failed rift. As the two active rifts continue to open, eventually the continental crust is attenuated as far as it will stretch, at this point basaltic oceanic crust begins to form between the separating continental fragments. When one of the rifts opens into the ocean, the rift system is flooded with seawater. The Red Sea is an example of a new arm of the sea, during this period of initial flooding the new sea is sensitive to changes in climate and eustasy. As a result, the new sea will evaporate several times before the elevation of the valley has been lowered to the point that the sea becomes stable. During this period of evaporation large evaporite deposits will be made in the rift valley, later these deposits have the potential to become hydrocarbon seals and are of particular interest to petroleum geologists
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African Plate
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The African Plate is a major tectonic plate straddling the equator as well as the prime meridian. It includes much of the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges, between 60 million years ago and 10 million years ago, the Somali Plate began rifting from the African Plate along the East African Rift. All of these are divergent or spreading boundaries with the exception of the northern boundary, the cratons are, from south to north, the Kalahari craton, Congo craton, Tanzania craton and West African craton. The cratons were widely separated in the past, but came together during the Pan-African orogeny, the cratons are connected by orogenic belts, regions of highly deformed rock where the tectonic plates have engaged. The African Plate is rifting in the interior of the African continent along the East African Rift. This rift zone separates the African Plate to the west from the Somali Plate to the east, the African Plates speed is estimated at around 2.15 cm per year. It has been moving over the past 100 million years or so in a general northeast direction and this is drawing it closer to the Eurasian Plate, causing subduction where oceanic crust is converging with continental crust. Along its northeast margin, the African Plate is bounded by the Red Sea Rift where the Arabian Plate is moving away from the African Plate. The New England hotspot in the Atlantic Ocean has probably created a line of mid- to late-Tertiary age seamounts on the African Plate. USGS - Understanding plate motions Meijer, P. Th, wortel, M. J. R. Cenozoic dynamics of the African plate with emphasis on the Africa-Eurasia collision. Journal of Geophysical Research, Solid Earth
35.
Indian Ocean
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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
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Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
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Shiva crater
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The Shiva Crater is a geologic structure, which is hypothesized by Sankar Chatterjee and colleagues to be a 500-km-diameter impact structure. This geologic structure consists of the Bombay High and Surat Depression and they lie beneath the Indian continental shelf and the Indian Ocean west of Mumbai, India. Chatterjee named this structure after Shiva, the Hindu god of destruction, Chatterjee argues that the Shiva Crater was created around 66 million years ago, about the same time as a number of other impact craters and the Cretaceous–Paleogene extinction event. Although the site has shifted since its formation because of sea floor spreading and it is estimated that this proposed crater would have been made by an asteroid or comet approximately 40 km in diameter. At the time of the Cretaceous–Paleogene extinction, India was located over the Réunion hotspot of the Indian Ocean, hot material rising from the mantle flooded portions of India with a vast amount of lava, creating a plateau known as the Deccan Traps. It has been hypothesized that either the crater or the Deccan Traps associated with the area are the reason for the level of oil. Earth scientists in general remain unconvinced that the Shiva Crater is indeed an impact crater, for example, Christian Koeberl, a professor of impact research and planetary geology at the University of Vienna, Austria, regards the Shiva Crater to be a figment of imagination. Currently, it is not recognized as a crater by the Earth Impact Database of the Planetary and Space Science Centre at the University of New Brunswick. Unlike typical known extraterrestrial impact structures, Shiva is teardrop shaped, Chatterjee argues that the low angle of an impact combined with boundary fault lines and unstable rock led to this unusual formation. The crater also is reported to contain larger than average amounts of alkaline rocks, shocked quartz. These types of rocks and features suggest an impact origin, the age of the crater is inferred from the Deccan traps, which contain relatively high amounts of iridium. Chatterjee is confident that Shiva was one of many impacts, stating that the K-T extinction was definitely a multiple-impact scenario, however, other scientists remain unconvinced that the extinction event was caused by multiple impacts, or that the Shiva feature is even in fact a crater. 60-8,2003 Seattle Annual Meeting of Geological Society of America, deep Impact - Shiva, Another K-T Impact. by Leslie Mullen for Astrobiology Magazine
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Geology of India
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The geology of India is diverse. Different regions of India contain rocks belonging to different geologic periods, some of the rocks are very deformed and altered. Other deposits include recently deposited alluvium that has yet to undergo diagenesis, mineral deposits of great variety are found in the Indian subcontinent in huge quantity. Even Indias fossil record is impressive in which stromatolites, invertebrates, vertebrates, Indias geographical land area can be classified into the Deccan Traps, Gondwana and Vindhyan. The Deccan Traps covers almost all of Maharashtra, a part of Gujarat, Karnataka, Madhya Pradesh, the melting broke through the surface of the craton in a massive flood basalt event, creating the Deccan Traps. It is also thought that the Reunion hotspot caused the separation of Madagascar, the Gondwana sediments forms a unique sequence of fluviatile rocks deposited in Permo-Carboniferous time. The Damodar and Sone river valleys and Rajmahal hills in the eastern India contain a record of the Gondwana rocks, the Indian Craton was once part of the supercontinent of Pangaea. At that time, what is now Indias southwest coast was attached to Madagascar and southern Africa, during the Jurassic Period about 160 Ma, rifting caused Pangaea to break apart into two supercontinents, namely Gondwana and Laurasia. The Indian Craton remained attached to Gondwana, until the supercontinent began to rift apart about in the early Cretaceous, the Indian Plate then drifted northward toward the Eurasian Plate, at a pace that is the fastest known movement of any plate. This orogeny, which is continuing today, is related to closure of the Tethys Ocean, the closure of this ocean which created the Alps in Europe, and the Caucasus range in western Asia, created the Himalaya Mountains and the Tibetan Plateau in South Asia. The current orogenic event is causing parts of the Asian continent to deform westward and eastward on either side of the orogen, concurrently with this collision, the Indian Plate sutured on to the adjacent Australian Plate, forming a new larger plate, the Indo-Australian Plate. These form the core of the Indian Craton, the Aravalli Range is the remnant of an early Proterozoic orogen called the Aravali-Delhi Orogen that joined the two older segments that make up the Indian Craton. It extends approximately 500 kilometres from its end to isolated hills and rocky ridges into Haryana. Minor igneous intrusions, deformation and subsequent metamorphism of the Aravalli Mountains represent the phase of orogenesis. The erosion of the mountains, and further deformation of the sediments of the Dharwarian group marks the second phase, the volcanic activities and intrusions, associated with this second phase are recorded in the composition of these sediments. Early to Late Proterozoic calcareous and arenaceous deposits, which correspond to humid and semi-arid climatic regimes, were deposited the Cuddapah and these basins which border or lie within the existing crystalline basement, were uplifted during the Cambrian. The sediments are generally undeformed and have in many places preserved their original horizontal stratification, the Vindhyans are believed to have been deposited between ~1700 and 650 Ma. Early Paleozoic rocks are found in the Himalayas and consist of southerly derived sediments eroded from the crystalline craton, in the Late Paleozoic, Permo-Carboniferous glaciations left extensive glacio-fluvial deposits across central India, in new basins created by sag/normal faulting
39.
Siberian Traps
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The Siberian Traps form a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The term traps is derived from the Swedish word for stairs, referring to the hills forming the landscape of the region. Vast volumes of lava covered a large expanse of Siberia in a flood basalt event. Today the area covered is about 2 million square kilometres —roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million square kilometres, the original volume of lava is estimated to range from 1 to 4 million cubic kilometres. The area covered lies between latitude 50° and 75° north and longitude 60° to 120° east, another possible cause may be the impact that formed the Wilkes Land crater, which may have been contemporaneous and would have been nearly antipodal to the Traps. This controversial scientific debate is ongoing, the Siberian Traps are considered to have erupted via numerous vents over a period of roughly a million years or more, probably east and south of Norilsk in Siberia. Individual eruptions of basalt lavas could have exceeded 2000 km3, the presence of extensive tuff and pyroclastic deposits suggests that a number of large explosive eruptions occurred during or before the eruptions of basaltic lavas. The presence of volcanic rocks such as rhyolite is also indicative of explosive eruptions. This massive eruptive event spanned the Permian-Triassic boundary, about 250 million years ago, one of the major questions is whether the Siberian Traps were directly responsible, or if they were themselves caused by some other, larger event, such as an asteroid impact. This extinction event, also called the Great Dying, affected all life on Earth, life on land took at least 30 million years to fully recover from the environmental disruptions which may have been caused by the eruption of the Siberian Traps. Calculations of sea temperature from δ18O measurements indicate that at its peak. The tetrapod gap of equatorial Pangea coincides with an end-Permian to Middle Triassic global coal gap that indicates the loss of peat swamps, the giant Norilsk-Talnakh nickel–copper–palladium deposit formed within the magma conduits in the main part of the Siberian Traps. Deccan Traps Emeishan Traps Viluy Traps The Siberian Traps by Richard Cowen The Siberian Traps Large Igneous Province Toxic Gases Caused Worlds Worst Mass Extinction
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Emeishan Traps
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The Emeishan Traps constitute a flood basalt volcanic province, or large igneous province, in south-western China, centred in Sichuan province. It is sometimes referred to as the Permian Emeishan Large Igneous Province or Emeishan Flood Basalts, like other volcanic provinces or traps, the Emeishan Traps are multiple layers of igneous rock laid down by large mantle plume volcanic eruptions. The Emeishan Traps eruptions were serious enough to have global ecological and paleontological impact and it is named for Emeishan, a mountain in Sichuan. The eruptions that produced the Emeishan Traps began 265 million years ago or earlier, the main eruptive period is between 262 Ma and 261 Ma, and the volcanism activities end 259 Ma. In volume, the Emeishan Traps are dwarfed by the massive Siberian Traps, thus the entire volume of the Emeishan basalts is estimated to be 0.3 ×106 km3. Evidence of Emeishan volcanology suggests that the volcanism of the central ELIP occurred in a deep submarine environment without any significantly pre-volcanic uplift. Intertrappean limestone show the extinction to occur immediately below the first eruptive unit, the onset of volcanism is violent phreatomagmatic-style eruptions forming volcaniclastics suggest that such effects are likely to have been severe. Siberian Traps Deccan Traps Viluy Traps Dobretsov, N. L, Large Igneous Provinces of Asia, Siberian and Emeishan traps and associated granitoids. He, Bin, Xu, Yi-Gang, Chung, Sun-Ling, Huang, Xiao-Long, Wang, sedimentary evidence for a rapid kilometer-scale crustal doming prior to the eruption of the Emeishan flood basalts. He, Bin, Xu, Yi-Gang, Huang, Xiao-Long, Luo, Zhen-Yu, Shi, Yu-Ruo, Yang, Qi-Jun, Yu, impact Markers in the Stratigraphic Record. Yuen, David A. Shinegoru Maruyama, Shun-Ichiro Karato, and Brian F. Windley, age of the Emeishan Flood Magmatism and Relations to Permian-Triassic Boundary Events. Nature - Re-evaluating plume-induced uplift in the Emeishan large igneous province Science - Volcanism, Mass Extinction, and Carbon Isotope Fluctuations in the Middle Permian of China
