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Geology Of Greenland
Greenland is the largest island on Earth. Only one-fifth of its surface area is exposed bedrock, the rest being covered by ice. The exposed surface is approximately 410,000 km2. The geology of Greenland is dominated by crystalline rocks of the Precambrian Shield."Greenland Geology." ''Geological Survey of Denmark and Greenland''. 20 June 2003 (retrieved 26 Dec 2010) The crystalline rocks of the Nuuk/Qeqertarsuatsiaat area comprise some of the oldest bedrock in Greenland which covers most of western Greenland. The surface has been altered several times and has an appearance as though it were shaped billions of years ago. This is one of the reasons why the Nuuk area is extraordinary and also because the particular climate zone for the area limits the vegetation which makes it p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanortalik
Nanortalik (, ), formerly Nennortalik, is a town in Nanortalik Island, Kujalleq municipalities of Greenland, municipality, southern Greenland. With 1,072 inhabitants as of 2024, it is the List of cities and towns in Greenland, eleventh-largest town in the country. The name ''Nanortalik'' means "Place of Polar bear, Polar Bears" or "Place Where the Polar Bears Go" (from ). It is the southernmost town in Greenland with a population of over 1,000. History Because of its location, this area was one of the first parts of Greenland settled by the Norsemen, Norse and one of the last settled by the Inuit. The town was founded in 1770 as Nennortalik. In 1797, a permanent trading depot was set up in Nanortalik by traders from Julianehåb. Due to poor harbour facilities, the town was moved three kilometers northward in 1830, where it remains today. Of the old town, only some scattered ruins remain. Geography Nanortalik is located on a small island (also named Nanortalik) on the shore ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Farish Jenkins
Farish Alston Jenkins (May 19, 1940 – November 11, 2012) was a professor at Harvard University who studied and taught paleontology. His discoveries included a transitional creature with characteristics of both fish and land animals, '' Tiktaalik roseae,'' and one of the earliest known frogs, ''Prosalirus bitis''. Early life Farish Jenkins was born in Manhattan on May 19, 1940. He was the oldest of three sons of a marketing executive but was raised by his grandmother in Colorado while his father served in World War II. Jenkins studied geology at Princeton, where he met his wife Eleanor Tracy. He served in the United States Marine Corps for four years, where he became a captain. After arriving to Yale in 1964 to continue his studies in geology, Jenkins took a trip to Nairobi where he is said to have taken his first interest in live animal research: "At the time, black rhinos in the bush were as thick as rats in a dump. With my camera set on self-timer, I managed to p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyostega
''Ichthyostega'', from Ancient Greek ἰχθύς (''ikthús''), meaning "fish", and στέγη (''stégē''), meaning "roof", is an Extinction, extinct genus of limbed tetrapodomorpha, tetrapodomorphs from the Devonian, Late Devonian of what is now Greenland. It was among the earliest four-limbed vertebrates ever in the fossil record and was one of the first with weight-bearing adaptations for terrestrial locomotion. ''Ichthyostega'' possessed lungs and limbs that helped it navigate through shallow water in swamps. Although ''Ichthyostega'' is often labelled a 'tetrapod' because of its limbs and fingers, it evolved long before true crown group tetrapods and could more accurately be referred to as a stegocephalian or stem tetrapod. Likewise, while undoubtedly of amphibian build and habit, it is not a true member of the group in the narrow sense, as the first modern amphibians (members of the group Lissamphibia) appeared in the Triassic Period. Until finds of other early stegocephal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthostega
''Acanthostega'', from Ancient Greek ἄκανθα (''ákantha''), meaning "spine", and στέγη (''stégē''), meaning "roof", is an extinct genus of stem tetrapoda, stem-tetrapod, among the first vertebrates, vertebrate animals to have recognizable Limb (anatomy), limbs. It appeared in the late Devonian period (Famennian age) about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and those that were able to come onto land. Discovery The fossilized remains are generally well preserved, with the famous fossil by which the significance of this species was discovered being found by Jennifer A. Clack in East Greenland in 1987, though fragments of the skull had been discovered in 1933 by Gunnar Säve-Söderbergh and Erik Jarvik. Description The ''Acanthostega'' Polydactyly in stem-tetrapods, had eight digits on each hand (the number of digits on the feet is unclear) linked by webbing. It lacked wrists, and was generally poorly adapted for wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Transition Zone
The transition zone is the part of Earth's mantle that is located between the lower and the upper mantle, most strictly between the seismic-discontinuity depths of about , but more broadly defined as the zone encompassing those discontinuities, i.e., between about depth. Earth's solid, rocky mantle, including the mantle transition zone (often abbreviated as MTZ), consists primarily of peridotite, an ultramafic igneous rock. The mantle was divided into the upper mantle, transition zone, and lower mantle as a result of sudden seismic-velocity discontinuities at depths of . This is thought to occur as a result of rearrangement of grains in olivine (which constitutes a large portion of peridotite) at a depth of , to form a denser crystal structure as a result of the increase in pressure with increasing depth. Below a depth of , evidence suggests due to pressure changes ringwoodite minerals change into two new denser phases, bridgmanite and periclase. This can be seen using bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core–mantle Boundary
The core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron–nickel outer core, at a depth of below Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the differences between the acoustic impedances of the solid mantle and the molten outer core. P-wave velocities are much slower in the outer core than in the deep mantle while S-waves do not exist at all in the liquid portion of the core. Recent evidence suggests a distinct boundary layer directly above the CMB possibly made of a novel phase of the basic perovskite mineralogy of the deep mantle named post-perovskite. Seismic tomography studies have shown significant irregularities within the boundary zone and appear to be dominated by the African and Pacific Large low-shear-velocity provinces (LLSVP). The uppermost section of the outer core is thought to be about 500–1,800 K hotter than the overlying mantle, creating a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Plume
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries. Concepts Mantle plumes were first proposed by J. Tuzo Wilson in 1963 and further developed by W. Jason Morgan in 1971 and 1972. A mantle plume is posited to exist where super-heated material forms ( nucleates) at the core-mantle boundary and rises through the Earth's mantle. Rather than a continuous stream, plumes should be viewed as a series of hot bubbles of material. Reaching the brittle upper Earth's crust they form diapirs. These diapirs are "hotspots" in the crust. In particular, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cumulate Rock
Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Cumulate rocks are named according to their texture; cumulate texture is diagnostic of the conditions of formation of this group of igneous rocks. Cumulates can be deposited on top of other older cumulates of different composition and colour, typically giving the cumulate rock a layered or banded appearance. Formation Cumulate rocks are the typical product of precipitation of solid crystals from a fractionating magma chamber. These accumulations typically occur on the floor of the magma chamber, although they are possible on the roofs if anorthite plagioclase is able to float free of a denser mafic melt. Cumulates are typically found in ultramafic intrusions, in the base of large ultramafic lava tubes in komatiite and magnesium rich basalt flows and also in some granitic intrusions. Terminology Cumulates are named according to their dominant mineralogy and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skaergaard Intrusion
The Skaergaard intrusion is a layered igneous intrusion in the Kangerlussuaq area of East Greenland and is composed of various rocks and minerals including gabbro, olivine, apatite, and basalt. History and background The Skaergaard intrusion was formed 56 million years ago during the opening of the North Atlantic Ocean. The intrusion was emplaced beneath the preexisting rock in the region, including plateau basalt and gneiss. The intrusion has a general oval shape, which is atypical in igneous emplacement. Due to the tectonic activity in East Greenland, the intrusion is now slightly tilted towards the sea. Specifically, the lower parts of the intrusion are exposed to the north while sections of the roof are conserved to the south. Discovery and early studies The Skaergaard intrusion was first discovered by Lawrence Wager on his Arctic Air-Route Expedition in 1930. In 1933, the first aerial photography of the region was taken in order to create a topographic map of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanogenic Massive Sulfide Ore Deposit
Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of metal sulfide Ore, ore deposit, mainly copper-zinc which are associated with and produced by volcanic-associated hydrothermal vents in submarine environments. These deposits are also sometimes called volcanic-hosted massive sulfide (VHMS) deposits. The density generally is 4500 kg/m3. They are predominantly Strata, stratiform accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings. In modern oceans they are synonymous with sulfurous plumes called black smokers. They occur within environments dominated by volcanic or volcanic derived (e.g., volcano-sedimentary) rocks, and the deposits are coeval and coincident with the formation of said volcanic rocks. As a class, they represent a significant source of the world's copper, zinc, lead, gold and silver ores, with cobalt, tin, barium, sulfur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metavolcanic
Metavolcanic rock is volcanic rock that shows signs of having experienced metamorphism. In other words, the rock was originally produced by a volcano, either as lava or tephra. The rock was then subjected to high pressure, high temperature or both, for example by burial under younger rocks, causing the original volcanic rock to recrystallize. Metavolcanic rocks are sometimes described informally as ''metavolcanics''. When it is possible to determine the original volcanic rock type from the properties of the metavolcanic rock (particularly if the degree of metamorphism is slight), the rock is more precisely named by appylying the prefix ''meta-'' to the original rock type. For example, a weakly metamorphosed basalt would be described as a '' metabasalt'', or a weakly metamorphosed tuff as a ''metatuff''. Metavolcanic rock is commonly found in greenstone belt Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
