A cinder cone is a steep conical hill of loose pyroclastic fragments, such as either volcanic clinkers, volcanic ash, or cinder, built around a volcanic vent. They consist of loose pyroclastic debris formed by explosive eruptions or lava fountains from a single cylindrical, vent; as the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone, symmetrical. Most cinder cones have a bowl-shaped crater at the summit; the rock fragments called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and cooled quickly. Cinder cones range in size from tens to hundreds of meters tall. Cinder cones are made of pyroclastic material. Many cinder cones have a bowl-shaped crater at the summit. During the waning stage of a cinder-cone eruption, the magma has lost most of its gas content; this gas-depleted magma does not fountain but oozes into the crater or beneath the base of the cone as lava.
Lava issues from the top because the loose, uncemented cinders are too weak to support the pressure exerted by molten rock as it rises toward the surface through the central vent. Because it contains so few gas bubbles, the molten lava is denser than the bubble-rich cinders. Thus, it burrows out along the bottom of the cinder cone, lifting the less dense cinders like a cork on water, advances outward, creating a lava flow around the cone's base; when the eruption ends, a symmetrical cone of cinders sits at the center of a surrounding pad of lava. If the crater is breached, the remaining walls form an amphitheatre or horseshoe shape around the vent. Cinder cones are found on the flanks of shield volcanoes and calderas. For example, geologists have identified nearly 100 cinder cones on the flanks of Mauna Kea, a shield volcano located on the island of Hawaii; these cones are referred to as'scoria cones' and'cinder and spatter cones.'The most famous cinder cone, grew out of a corn field in Mexico in 1943 from a new vent.
Eruptions continued for nine years, built the cone to a height of 424 meters, produced lava flows that covered 25 km². The Earth's most active cinder cone is Cerro Negro in Nicaragua, it is part of a group of four young cinder cones NW of Las Pilas volcano. Since its initial eruption in 1850, it has erupted more than 20 times, most in 1995 and 1999. Based on satellite images it was suggested that cinder cones might occur on other terrestrial bodies in the solar system too, they were reported on the flanks of Pavonis Mons in Tharsis, in the region of Hydraotes Chaos on the bottom of the Coprates Chasma, or in the volcanic field Ulysses Colles. It is suggested that domical structures in Marius Hills might represent lunar cinder cones; the size and shape of cinder cones depend on environmental properties as different gravity and/or atmospheric pressure might change the dispersion of ejected scoria particles. For example, cinder cones on Mars seem to be more than two times wider than terrestrial analogues as lower atmospheric pressure and gravity enable wider dispersion of ejected particles over a larger area.
Therefore, it seems that erupted amount of material is not sufficient on Mars for the flank slopes to attain the angle of repose and Martian cinder cones seem to be ruled by ballistic distribution and not by material redistribution on flanks as typical on Earth. Some cinder cones are monogenetic -- the result of a never-to-be-repeated eruption. Parícutin in Mexico, Diamond Head, Koko Head, Punchbowl Crater and some cinder cones on Mauna Kea are monogenetic cinder cones. Monogenetic eruptions can last for more than 10 years. Parícutin erupted from 1943 to 1952. List of cinder cones Volcanic cone – Landform of ejecta from a volcanic vent piled up in a conical shape Capulin Volcano National Monument
Monticellite and kirschsteinite are gray silicate minerals of the olivine group with compositions CaMgSiO4 and CaFeSiO4, respectively. Most monticellites have the pure magnesium end-member composition but rare ferroan monticellites and magnesio-kirschsteinite are found with between 30 and 75 mol.% of the iron end member. Pure kirschsteinite is only found in synthetic systems. Monticellite is named after Teodoro Monticelli Italian mineralogist. Like other members of the group monticellite and kirschsteinite have orthorhombic unit cells shown in Figure 1. Iron and magnesium ions are located on the M1 inversion sites and calcium ions occupy the M2 site on mirror planes; the unit cell is somewhat larger than for the calcium free olivines forsterite and fayalite with a = 0.4815 nm, b = 1.108 nm and c = 0.637 nm,and for monticellite a = 0.4875 nm, b = 1.1155 nm and c = 0.6438 nm. Deer, W. A. Howie, R. A. and Zussman, J.. An introduction to the rock-forming minerals. Harlow: Longman ISBN 0-582-30094-0 Mindat.org Webmineral.com Handbook of Mineralogy
Talc is a clay mineral composed of hydrated magnesium silicate with the chemical formula Mg3Si4O102. Talc in powdered form in combination with corn starch, is a used substance known as baby powder; this mineral is used as a thickening agent and lubricant, is an ingredient in ceramics and roofing material, is one of the main ingredients in many cosmetic products. It occurs as foliated to fibrous masses, in an exceptionally rare crystal form, it has a perfect basal cleavage, uneven flat fracture and it is foliated with a two dimensional platy form. The Mohs scale of mineral hardness is based on scratch hardness comparison, ranging from 1-10, a value of 10 being the hardest of minerals. Talc is the defining value 1 therefore the softest of minerals. Any mineral below a value of 2 on Mohs scale of mineral hardness can be scratched by a fingernail; when scraped on a streak plate it produces a white streak, though this indicator is of little importance because most silicate minerals produce a white streak.
Talc is translucent to opaque with colors ranging from whitish grey to green with a vitreous and pearly luster. Talc is not soluble in water, but is soluble in dilute mineral acids. Soapstone is a well known metamorphic rock composed predominantly of talc; the word "talc" derives from Medieval Latin talcum, which in turn originates from Arabic: طلق ṭalq which, derives from Persian: تالک tālk. In ancient times, the word was used for various related minerals, including talc and selenite. Talc is a mineral that results from the metamorphism of magnesian minerals such as serpentine, pyroxene and olivine, in the presence of carbon dioxide and water; this is known as "talc carbonation" or "steatization" and produces a suite of rocks known as talc carbonates. Talc is formed by hydration and carbonation by this reaction: serpentine2 Mg3Si2O54 + carbon dioxide3CO2 → talcMg3Si4O102 + magnesite3 MgCO3 + water3 H2OTalc can be formed via a reaction between dolomite and silica, typical of skarnification of dolomites by silica-flooding in contact metamorphic aureoles: dolomite3 CaMg2 + silica4 SiO2 + waterH2O → talcMg3Si4O102 + calcite3 CaCO3 + carbon dioxide3 CO2Talc can be formed from magnesian chlorite and quartz in blueschist and eclogite metamorphism by the following metamorphic reaction: chlorite + quartz → kyanite + talc + waterIn this reaction, the ratio of talc and kyanite depends on aluminium content, with more aluminous rocks favoring production of kyanite.
This is associated with high-pressure, low-temperature minerals such as phengite and glaucophane within the lower blueschist facies. Such rocks are white and fibrous, are known as whiteschist. Talc is a trioctahedral layered mineral. Talc is a common metamorphic mineral in metamorphic belts that contain ultramafic rocks, such as soapstone, within whiteschist and blueschist metamorphic terranes. Prime examples of whiteschists include the Franciscan Metamorphic Belt of the western United States, the western European Alps in Italy, certain areas of the Musgrave Block, some collisional orogens such as the Himalayas, which stretch along Pakistan, India and Bhutan. Talc carbonate ultramafics are typical of many areas of the Archaean cratons, notably the komatiite belts of the Yilgarn Craton in Western Australia. Talc-carbonate ultramafics are known from the Lachlan Fold Belt, eastern Australia, from Brazil, the Guiana Shield, from the ophiolite belts of Turkey and the Middle East. China is the key world talc and steatite producing country with an output of about 2.2M tonnes, which accounts for 30% of total global output.
The other major producers are Brazil, the U. S. France, Italy, Russia and Austria. Notable economic talc occurrences include the Mount Seabrook talc mine, Western Australia, formed upon a polydeformed, layered ultramafic intrusion; the France-based Luzenac Group is the world's largest supplier of mined talc. Its largest talc mine at Trimouns near Luzenac in southern France produces 400,000 tonnes of talc per year. Extraction in disputed areas of Nangarhar province, has led the international monitoring group Global Witness to declare talc a conflict mineral, as the profits are used to fund armed confrontation between the Taliban and Islamic State. Talc is used in many industries, including paper making, plastic and coatings, food, electric cable, pharmaceuticals and ceramics. A coarse grayish-green high-talc rock is soapstone or steatite, used for stoves, electrical switchboards, etc, it is used for surfaces of laboratory table tops and electrical switchboards because of its resistance to heat and acids.
In finely ground form, talc finds use as a cosmetic, as a lubricant, as a filler in paper manufacture. It is used to coat the insides of inner tubes and rubber gloves during manufacture to keep the surfaces from sticking. Talcum powder, with heavy refinement, has been used in baby powder, an astringent powder used to prevent diaper rash; the American Academy of Pediatrics recommends that parents not use baby powder because it poses a risk of respiratory problems, including breathing trouble and serious lung damage if the baby inhales it. The small size of the particles makes it difficult to keep them out of the air while applying the powder. Zinc oxide-based ointments are a much safer alternative, it is often used in basketball to keep a player's hands dry. Most tailor's chalk, or French chalk, is talc, as is the chalk used for welding or metalworki
A dike or dyke, in geological usage, is a sheet of rock, formed in a fracture in a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed. An intrusive dike is an igneous body with a high aspect ratio, which means that its thickness is much smaller than the other two dimensions. Thickness can vary from sub-centimeter scale to many meters, the lateral dimensions can extend over many kilometres. A dike is an intrusion into an opening cross-cutting fissure, shouldering aside other pre-existing layers or bodies of rock. Dikes are high-angle to near-vertical in orientation, but subsequent tectonic deformation may rotate the sequence of strata through which the dike propagates so that the dike becomes horizontal. Near-horizontal, or conformable intrusions, along bedding planes between strata are called intrusive sills.
The term "sheet" is the general term for both sills. Sometimes dikes appear in swarms, consisting of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event; the world's largest dike swarm is the Mackenzie dike swarm in Canada. Dikes form as either radial or concentric swarms around plutonic intrusives, volcanic necks or feeder vents in volcanic cones; the latter are known as ring dikes. Dikes can vary in texture and their composition can range from diabase or basaltic to granitic or rhyolitic, but on a global perspective the basaltic composition prevails, manifesting ascent of vast volumes of mantle-derived magmas through fractured lithosphere throughout Earth history. Pegmatite dikes comprise coarse crystalline granitic rocks - associated with late-stage granite intrusions or metamorphic segregations. Aplite dikes are sugary-textured intrusives of granitic composition; the term "feeder dike" is used for a dike. Magma flowed along out of the dike formed another feature.
In contrast to magmatic dikes, a sill is a magmatic sheet intrusion that forms within and parallel to the bedding of layered rock. Sedimentary dikes or clastic dikes are vertical bodies of sedimentary rock that cut off other rock layers, they can form in two ways: When a shallow unconsolidated sediment is composed of alternating coarse grained and impermeable clay layers the fluid pressure inside the coarser layers may reach a critical value due to lithostatic overburden. Driven by the fluid pressure the sediment forms a dike; when a soil is under permafrost conditions the pore water is frozen. When cracks are formed in such rocks, they may fill up with sediments; the result is a vertical body of sediment that cuts through a dike. Batholith Ring dike Fissure vent – Linear volcanic vent through which lava erupts Laccolith Runamo – A cracked dolerite dike in Sweden, for centuries held to be a runic inscription interpreted as a runic inscription. Dike swarm Sill
Iron is a chemical element with symbol Fe and atomic number 26. It is a metal, that belongs to group 8 of the periodic table, it is by mass the most common element on Earth, forming much of Earth's inner core. It is the fourth most common element in the Earth's crust. Pure iron is rare on the Earth's crust being limited to meteorites. Iron ores are quite abundant, but extracting usable metal from them requires kilns or furnaces capable of reaching 1500 °C or higher, about 500 °C higher than what is enough to smelt copper. Humans started to dominate that process in Eurasia only about 2000 BCE, iron began to displace copper alloys for tools and weapons, in some regions, only around 1200 BCE; that event is considered the transition from the Bronze Age to the Iron Age. Iron alloys, such as steel and special steels are now by far the most common industrial metals, because of their mechanical properties and their low cost. Pristine and smooth pure iron surfaces are mirror-like silvery-gray. However, iron reacts with oxygen and water to give brown to black hydrated iron oxides known as rust.
Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion. The body of an adult human contains about 3 to 5 grams of elemental iron in hemoglobin and myoglobin; these two proteins play essential roles in vertebrate metabolism oxygen transport by blood and oxygen storage in muscles. To maintain the necessary levels, human iron metabolism requires a minimum of iron in the diet. Iron is the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. Chemically, the most common oxidation states of iron are +2 and +3. Iron shares many properties of other transition metals, including the other group 8 elements and osmium. Iron forms compounds in a wide range of oxidation states, −2 to +7. Iron forms many coordination compounds. At least four allotropes of iron are known, conventionally denoted α, γ, δ, ε; the first three forms are observed at ordinary pressures.
As molten iron cools past its freezing point of 1538 °C, it crystallizes into its δ allotrope, which has a body-centered cubic crystal structure. As it cools further to 1394 °C, it changes to its γ-iron allotrope, a face-centered cubic crystal structure, or austenite. At 912 °C and below, the crystal structure again becomes the bcc α-iron allotrope; the physical properties of iron at high pressures and temperatures have been studied extensively, because of their relevance to theories about the cores of the Earth and other planets. Above 10 GPa and temperatures of a few hundred kelvin or less, α-iron changes into another hexagonal close-packed structure, known as ε-iron; the higher-temperature γ-phase changes into ε-iron, but does so at higher pressure. Some controversial experimental evidence exists for a stable β phase at pressures above 50 GPa and temperatures of at least 1500 K, it is supposed to have a double hcp structure. The inner core of the Earth is presumed to consist of an iron-nickel alloy with ε structure.
The melting and boiling points of iron, along with its enthalpy of atomization, are lower than those of the earlier 3d elements from scandium to chromium, showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus. This same trend appears for ruthenium but not osmium; the melting point of iron is experimentally well defined for pressures less than 50 GPa. For greater pressures, published data still varies by tens of gigapascals and over a thousand kelvin. Below its Curie point of 770 °C, α-iron changes from paramagnetic to ferromagnetic: the spins of the two unpaired electrons in each atom align with the spins of its neighbors, creating an overall magnetic field; this happens because the orbitals of those two electrons do not point toward neighboring atoms in the lattice, therefore are not involved in metallic bonding. In the absence of an external source of magnetic field, the atoms get spontaneously partitioned into magnetic domains, about 10 micrometres across, such that the atoms in each domain have parallel spins, but different domains have other orientations.
Thus a macroscopic piece of iron will have a nearly zero overall magnetic field. Application of an external magnetic field causes the domains that are magnetized in the same general direction to grow at the expense of adjacent ones that point in other directions, reinforcing the external field; this effect is exploited in devices that needs to channel magnetic fields, such as electrical transformers, magnetic recording heads, electric motors. Impurities, lattice defects, or grain and particle boundaries can "pin" the domains in the new positions, so that the effect persists after the external field is removed -- thus turning the iron object into a magnet. Similar behavior is exhibited by some iron compounds, such as the fer
Western Australia is a state occupying the entire western third of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, South Australia to the south-east. Western Australia is Australia's largest state, with a total land area of 2,529,875 square kilometres, the second-largest country subdivision in the world, surpassed only by Russia's Sakha Republic; the state has about 2.6 million inhabitants – around 11 percent of the national total – of whom the vast majority live in the south-west corner, 79 per cent of the population living in the Perth area, leaving the remainder of the state sparsely populated. The first European visitor to Western Australia was the Dutch explorer Dirk Hartog, who visited the Western Australian coast in 1616; the first European settlement of Western Australia occurred following the landing by Major Edmund Lockyer on 26 December 1826 of an expedition on behalf of the New South Wales colonial government.
He established a convict-supported military garrison at King George III Sound, at present-day Albany, on 21 January 1827 formally took possession of the western third of the continent for the British Crown. This was followed by the establishment of the Swan River Colony in 1829, including the site of the present-day capital, Perth. York was the first inland settlement in Western Australia. Situated 97 kilometres east of Perth, it was settled on 16 September 1831. Western Australia achieved responsible government in 1890 and federated with the other British colonies in Australia in 1901. Today, its economy relies on mining, agriculture and tourism; the state produces 46 per cent of Australia's exports. Western Australia is the second-largest iron ore producer in the world. Western Australia is bounded to the east by longitude 129°E, the meridian 129 degrees east of Greenwich, which defines the border with South Australia and the Northern Territory, bounded by the Indian Ocean to the west and north.
The International Hydrographic Organization designates the body of water south of the continent as part of the Indian Ocean. The total length of the state's eastern border is 1,862 km. There are 20,781 km including 7,892 km of island coastline; the total land area occupied by the state is 2.5 million km2. The bulk of Western Australia consists of the old Yilgarn craton and Pilbara craton which merged with the Deccan Plateau of India and the Karoo and Zimbabwe cratons of Southern Africa, in the Archean Eon to form Ur, one of the oldest supercontinents on Earth. In May 2017, evidence of the earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits uncovered in the Pilbara craton. Because the only mountain-building since has been of the Stirling Range with the rifting from Antarctica, the land is eroded and ancient, with no part of the state above 1,245 metres AHD. Most of the state is a low plateau with an average elevation of about 400 metres low relief, no surface runoff.
This descends sharply to the coastal plains, in some cases forming a sharp escarpment. The extreme age of the landscape has meant that the soils are remarkably infertile and laterised. Soils derived from granitic bedrock contain an order of magnitude less available phosphorus and only half as much nitrogen as soils in comparable climates in other continents. Soils derived from extensive sandplains or ironstone are less fertile, nearly devoid of soluble phosphate and deficient in zinc, copper and sometimes potassium and calcium; the infertility of most of the soils has required heavy application by farmers of fertilizers. These have resulted in damage to bacterial populations; the grazing and use of hoofed mammals and heavy machinery through the years have resulted in compaction of soils and great damage to the fragile soils. Large-scale land clearing for agriculture has damaged habitats for native fauna; as a result, the South West region of the state has a higher concentration of rare, threatened or endangered flora and fauna than many areas of Australia, making it one of the world's biodiversity "hot spots".
Large areas of the state's wheatbelt region have problems with dryland salinity and the loss of fresh water. The southwest coastal area has a Mediterranean climate, it was heavily forested, including large stands of karri, one of the tallest trees in the world. This agricultural region is one of the nine most bio-diverse terrestrial habitats, with a higher proportion of endemic species than most other equivalent regions. Thanks to the offshore Leeuwin Current, the area is one of the top six regions for marine biodiversity and contains the most southerly coral reefs in the world. Average annual rainfall varies from 300 millimetres at the edge of the Wheatbelt region to 1,400 millimetres in the wettest areas near Northcliffe, but from November to March, evaporation exceeds rainfall, it is very dry. Plants are adapted to this as well as the extreme poverty of all soils; the central two-thirds of the state is sparsely inhabited. The only significant economic activity is mining. Annual rainfall averages less than 300 millimetres, most of which occurs in sporadic torrential falls related to cyclone events in summer.
An exception to this is
The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and with the end of the Paleolithic age used in archaeology; the Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Middle Pleistocene and Upper Pleistocene. In addition to this international subdivision, various regional subdivisions are used. Before a change confirmed in 2009 by the International Union of Geological Sciences, the time boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 million years Before Present, as opposed to the accepted 2.588 million years BP: publications from the preceding years may use either definition of the period. Charles Lyell introduced the term "Pleistocene" in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today.
This distinguished it from the older Pliocene epoch, which Lyell had thought to be the youngest fossil rock layer. He constructed the name "Pleistocene" from the Greek πλεῖστος, pleīstos, "most", καινός, kainós, "new"; the Pleistocene has been dated from 2.588 million to 11,700 years BP with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell; the end of the Younger Dryas has been dated to about 9640 BC. The end of the Younger Dryas is the official start of the current Holocene Epoch. Although it is considered an epoch, the Holocene is not different from previous interglacial intervals within the Pleistocene, it was not until after the development of radiocarbon dating, that Pleistocene archaeological excavations shifted to stratified caves and rock-shelters as opposed to open-air river-terrace sites. In 2009 the International Union of Geological Sciences confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP.
The IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point, for the upper Pleistocene/Holocene boundary. The proposed section is the North Greenland Ice Core Project ice core 75° 06' N 42° 18' W; the lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: Discoaster pentaradiatus and Discoaster surculus; the Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age; the revised definition of the Quaternary, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene. The modern continents were at their present positions during the Pleistocene, the plates upon which they sit having moved no more than 100 km relative to each other since the beginning of the period.
According to Mark Lynas, the Pleistocene's overall climate could be characterized as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru, warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, other El Niño markers. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places, it is estimated. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America, several hundred in Eurasia; the mean annual temperature at the edge of the ice was −6 °C. Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres thick, resulting in temporary sea-level drops of 100 metres or more over the entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions.
The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene; the Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Tasmania; the current decaying glaciers of Mount Kenya, Mount Kilimanjaro, the Ruwenzori Range in east and central Africa were larger. Glaciers existed to the west in the Atlas mountains. In the northern hemisphere, many glaciers fused into one; the Cordilleran ice sheet covered the North American northwest. The Fenno-Scandian ice sheet rested including much of Great Britain. Scattered domes stretched across Siberi