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Haig Fras
Haig Fras is a 45 km long submarine granitic rocky outcrop in the southern part of the Celtic Sea, lying about 95 km northwest of the Isles of Scilly. It covers an area of . At one point it reaches within 38 m of the sea surface. It is protected as a Special Area of Conservation (SAC) because of the diverse fauna developed in its bedrock reef habitat. It was discovered in 1962 and named by Smith and others in 1965. Geology The Haig Fras outcrop consists mainly of granite, forming a WSW-ENE trending elongate intrusion. The granite outcrop is surrounded by an area of Devonian- Carboniferous sedimentary rocks. Evidence from gravity data suggests that the extent of the intrusion is greater than the observed outcrop, based on its association with a linear negative gravity anomaly. It is dated at 277 Ma, Early Permian in age, within the range of intrusion ages for the granites that make up the Cornubian batholith. Although the two intrusions have the same trend and are o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornubian Batholith
The Cornubian batholith is a large mass of granite rock, formed about 280 million years ago, which lies beneath much of Devon and Cornwall, the south-western peninsula of Great Britain. The main exposed masses of granite are seen at Dartmoor, Bodmin Moor, St Austell, Carnmenellis, Land's End and the Isles of Scilly. The intrusion is associated with significant quantities of minerals particularly cassiterite, an ore of tin which has been mined since about 2000 BC. Other minerals include china clay and ores of copper, lead, zinc and tungsten. It takes its name from ''Cornubia'', the Medieval Latin name for Cornwall. Extent and geometry A batholith is a large mass of intrusive rock formed from the crystallization of molten rock beneath the Earth's surface (magma). From gravity and magnetic geophysical data, the batholith is interpreted to extend from about 8°W, more than 100 km southwest of the Isles of Scilly, to the eastern edge of Dartmoor. The negative gravity anomaly, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiometric Dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of Earth itself, and can also be used to date a wide range of natural and man-made materials. Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale. Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating. By al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bitectiporidae
The Bitectiporidae is a family within the bryozoan order Cheilostomatida. Colonies are encrusting on shells and rocks or upright bilaminar branches or sheets. The zooids generally have at least one adventitious avicularia on their frontal wall near the orifice. The frontal wall is usually covered with small pores and numerous larger pores along the margin. The ovicell, which broods the larvae internally, is double-layered with numerous pores in the outer layer, and sits quite prominently on the frontal wall of the next zooid. Classification * Family Bitectiporidae ** Genus '' Bitectipora'' ** Genus ''Cribella'' ** Genus '' Hippomonavella'' ** Genus '' Hippoporina'' ** Genus '' Hippothyris'' ** Genus '' Kermadecazoon'' ** Genus '' Metroperiella'' ** Genus '' Neodakaria'' ** Genus '' Nigrapercula'' ** Genus '' Parkermavella'' ** Genus ''Pentapora ''Pentapora'' is a small genus of bryozoans in the family Bitectiporidae. Species The World Register of Marine Species lists the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crinoid
Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths as great as . Adult crinoids are characterised by having the mouth located on the upper surface. This is surrounded by feeding arms, and is linked to a U-shaped gut, with the anus being located on the oral disc near the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, in most crinoids the five arms are subdivided into ten or more. These have feathery pinnules and are spread wide to gather planktonic particles from the water. At some stage in their lives, most crinoids have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caryophylliidae
The Caryophylliidae are a family of stony corals found from the tropics to temperate seas, and from shallow to very deep water. Genera *'' Africana'' Ocana & Brito, 2015 *'' Anomocora'' Studer, 1878 *'' Asterosmilia'' Duncan, 1867 *'' Aulocyathus'' Marenzeller, 1904 *'' Bathycyathus'' Milne-Edwards & Haime, 1848 *'' Bourneotrochus'' Wells, 1984 *'' Brachytrochus'' † Reuss, 1864 *'' Caryophyllia'' Lamarck, 1801 *'' Ceratotrochus'' Milne-Edwards & Haime, 1848 *'' Coelosimilia'' † *'' Coenocyathus'' Milne-Edwards & Haime, 1848 *'' Coenosmilia'' Pourtalès, 1874 *''Colangia ''Colangia'' is a genus of small corals in the Family (biology), family Caryophylliidae. Species The World Register of Marine Species includes the following species in the genus : * ''Colangia immersa'' Louis François de Pourtalès, Pourtalès, ...'' Pourtalès, 1871 *'' Concentrotheca'' Cairns, 1979 *'' Confluphyllia'' Zibrowius & Cairns, 1997 *'' Conotrochus'' Sequenza, 1864 *'' Crispatotrochus'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corynactis
''Corynactis'' is a genus of colonial anthozoans similar in appearance to sea anemones and in body format to scleractinian stony corals. These animals are cnidarians in the family Corallimorphidae. Large unidentified polyps of this genus feed on the crown-of-thorns seastar ''Acanthaster planci'' and may help control the crown-of-thorns population. Species Species so far described in this genus include: *''Corynactis annulata'' Verrill, 1867 *''Corynactis australis'' Haddon & Duerden, 1896 *''Corynactis caboverdensis'' den Hartog, Ocaña & Brito, 1993 *''Corynactis californica'' Carlgren, 1936 *''Corynactis caribbeorum'' den Hartog, 1980 *''Corynactis carnea'' Studer, 1879 *''Corynactis chilensis'' Carlgren, 1941 *''Corynactis delawarei'' Widersten, 1976 *''Corynactis denhartogi'' Ocaña, 2003 *''Corynactis denticulosa'' Le Sueur, 1817 *''Corynactis globulifera'' Hemprich & Ehrenberg in Ehrenberg, 1834 *''Corynactis parvula'' Duchassaing & Michelotti, 1860 *''Corynactis sanmatiens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caryophyllia Smithii Stokes & Broderip, 1828
''Caryophyllia'' is a genus of solitary corals in the family Caryophylliidae. Members of this genus are azooxanthellate (do not contain symbiotic algae) and are found in the North Atlantic Ocean and the Mediterranean Sea at depths down to . Subgenera The genus has two subgenera and the following species according to the World Register of Marine Species:- * Subgenus ''Acanthocyathus'' Milne Edwards & Haime, 1848 ** '' Caryophyllia decamera'' Cairns, 1998 ** '' Caryophyllia dentata'' (Moseley, 1881) ** '' Caryophyllia grayi'' (Milne Edwards & Haime, 1848) ** '' Caryophyllia karubarica'' Cairns & Zibrowius, 1997 ** '' Caryophyllia quangdongensis'' Zou, 1984 ** '' Caryophyllia spinicarens'' (Moseley, 1881) ** '' Caryophyllia spinigera'' ( Saville-Kent, 1871) ** '' Caryophyllia unicristata'' Cairns & Zibrowius, 1997 ** '' Caryophyllia zanzibarensis'' Zou, 1984 * Subgenus ''Caryophyllia'' Lamarck, 1801 ** '' Caryophyllia abrupta'' Cairns, 1999 ** '' Caryophyllia abyssorum'' Duncan, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian reptiles, like the dinosaurs; an abundance of conifers and ferns; a hot Greenhouse and icehouse earth, greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since Cambrian explosion, complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic. The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs, Pterosaur, pterosaurs, Mosasaur, mosasaurs, and Plesiosaur, plesiosaurs. The Mesozoic was a time of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection Seismology
Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized air gun or a seismic vibrator. Reflection seismology is similar to sonar and echolocation. This article is about surface seismic surveys; for vertical seismic profiles, see VSP. History Reflections and refractions of seismic waves at geologic interfaces within the Earth were first observed on recordings of earthquake-generated seismic waves. The basic model of the Earth's deep interior is based on observations of earthquake-generated seismic waves transmitted through the Earth's interior (e.g., Mohorovičić, 1910). The use of human-generated seismic waves to map in detail the geology of the upper few kilometers of the Earth's crust followed shortly thereafter and h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dike (geology)
A dike or dyke, in Geology, geological usage, is a sheet of rock that is formed in a Fracture (geology), fracture of a pre-existing rock body. Dikes can be either Intrusive rock, magmatic or Sedimentary rock, sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack.Essentials of Geology, 3rd Ed, Stephen Marshak Magmatic dikes A magmatic dike is a sheet of igneous rock that cuts across older rock beds. It is formed when magma fills a fracture in the older beds and then cools and solidifies. The dike rock is usually more resistant to weathering than the surrounding rock, so that erosion exposes the dike as a natural wall or ridge. It is from these natural walls that dikes get their name. Dikes preserve a record of the fissures through which most mafic magma (fluid magma low in silica) reac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar. Mafic materials can also be described as ferromagnesian. History The term ''mafic'' is a portmanteau of "magnesium" and "ferric" and was coined by Charles Whitman Cross, Joseph P. Iddings, Louis Valentine Pirsson, and Henry Stephens Washington in 1912. Cross' group had previously divided the major rock-forming minerals found in igneous rocks into ''salic'' minerals, such as quartz, feldspars, or feldspathoids, and ''femic'' minerals, such as olivine and pyroxene. However, micas and aluminium-rich amphiboles were excluded, while some calcium minerals containing little iron or magnesium, such as wollastonite or apatite, were included ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dike Swarm
A dike swarm (American spelling) or dyke swarm (British spelling) is a large geological structure consisting of a major group of parallel, linear, or radially oriented magmatic dikes intruded within continental crust or central volcanoes in rift zones. Examples exist in Iceland and near other large volcanoes, (stratovolcanoes, calderas, shield volcanoes and other fissure systems) around the world. They consist of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event, are magmatic and stratigraphic, and may form a large igneous province. The occurrence of mafic dike swarms in Archean and Paleoproterozoic terrains is often cited as evidence for mantle plume activity associated with abnormally high mantle potential temperatures. Dike swarms may extend over in width and length. The largest dike swarm known on Earth is the Mackenzie dike swarm in the western half of the Canadian Shield in Canada, which is more than wide and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
