The olivine-rich picrite basalts that occur with the more common tholeiitic basalts of Klauea and other volcanoes of the Hawaiian Islands are the result of Hence most oceanic crust is the same thickness (71 km). 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.. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater.For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has olivine, any member of a group of common magnesium, iron silicate minerals. Some eruptions cooled the global climateinducing a volcanic winterdepending on Viscosity depends on primarily on the composition of the magma, and temperature. A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft).Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.However, rarer intermediate composition and mafic pegmatites are known. Once melting begins, the process changes to an igneous process rather than a metamorphic process. Six locations were sampled directly during the crewed Apollo program landings from 1969 to 1972, which returned 380.96 kilograms (839.9 lb) of lunar rock and lunar soil to Earth. Mafic refers to silicate crystals, magmas, and rocks with a high proportion of heavier elements. The name "mafic magma" comes from the combination of the letters MA and FIC, which stand for magnesium and iron in Latin. The behavior of lava flows is mostly determined by the lava's viscosity. The temperatures of molten lava range from about 700 to 1,200 C (1,300 to 2,200 F). Temperature: Viscosity: Gas Content: Basaltic: Basalt: 45-55 SiO 2 %, high in Fe, Mg, Ca, low in K, Na: Intermediate magma has higher silica content (roughly 60%) than mafic magma but lower than felsic magma. Mafic magmas have high melting temperatures and low viscosity. The magma causes a type of metamorphism called contact metamorphism (to be discussed later). Olivines are an important rock-forming mineral group. The term lava is also used for the solidified rock formed by the cooling of a molten lava flow. Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.. Anorthosites are of enormous geologic interest, because it is still not fully understood how they the characteristics like temperature, ash content, composition of elements in magma, etc., determine the shapes or forms of volcanic formations on solidification. Mafic and Felsic Both are made-up terms used to indicate the chemical composition of silicate minerals, magmas, and igneous rocks. Igneous rocks are formed from the solidification of magma, which is a hot (600 to 1,300 C, or 1,100 to 2,400 F) molten or The rock will have some relatively large crystals (phenocrysts) of the minerals that crystallized early, and the rest will be very fine grained or even glassy. They are typified by their high ferromagnesian content, and generally erupt at temperatures of 1,100 to 1,200 C (2,010 to 2,190 F). Mafic or basaltic magmas have a silica content of 52% to 45%. Picrite basalt or picrobasalt is a variety of high-magnesium olivine basalt that is very rich in the mineral olivine.It is dark with yellow-green olivine phenocrysts (20-50%) and black to dark brown pyroxene, mostly augite.. METAMORPHIC ROCKS form when a sedimentary or igneous rock is exposed to high pressure, high temperature, or both, deep below the surface of the Earth. Other volcanic eruptions are also listed. In general more siliceous magmas form by low degrees of partial melting. While the temperature of common silicate lava ranges from about 800 C (1,470 F) for felsic lavas to 1,200 C (2,190 F) for mafic lavas, its viscosity ranges over seven orders of magnitude, from 10 11 cP (10 8 Pas) for felsic lavas to 10 4 cP (10 Pas) for mafic lavas. This timeline of volcanism on Earth includes a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic explosivity index (VEI) or equivalent sulfur dioxide emission during the Quaternary period (from 2.58 Mya to the present). Basaltic (or mafic) magma predominates in nonexplosive volcanic eruptions. As a magma cools below 1300C, minerals start to crystallize within it. The temperature and pressure in continental-continental convergence are so intense that it can create volcanoes. Fractional crystallization is the removal and segregation from a melt of mineral precipitates; except in special cases, removal of the crystals changes the composition of the magma. It formed the eastern Snake River Plain through a succession of caldera-forming eruptions.The resulting calderas include the Island Park Caldera, Henry's Fork Composition also determines what minerals are present in igneous rocks. The material can be very fluid, flowing almost like syrup, or it can be extremely stiff, scarcely flowing at all. Mafic rocks contain minerals that are high in magnesium and/or iron such as olivine, pyroxene, amphibole, magnetite, as well as plagioclase feldspar. The individual rock fragments are known as pyroclasts.Pyroclastic rocks are a type of volcaniclastic deposit, which are deposits made predominantly of volcanic particles. Magnesium-rich olivines are abundant in low-silica mafic and ultramafic igneous rocks and are believed to be the most abundant constituent of the Earths upper mantle. Temperature of Magmas Temperature of magmas is difficult to measure (due to the danger involved), but laboratory measurement and limited field observation indicate that the eruption temperature of various magmas is as follows: Basaltic magma - 1000 to 1200 o C; Andesitic magma - 800 to 1000 o C; Rhyolitic magma - 650 to 800 o C. In essence, fractional crystallization is the removal of early formed crystals from an originally homogeneous magma (for example, by gravity settling) so that these crystals are Pyroclastic rocks (derived from the Greek: , meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. Anorthosite (/ n r s a t /) is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90100%), with a minimal mafic component (010%). The Earth's mantle is The more mafic nature of the crust meant that higher amounts of water molecules could be stored the altered parts of the crust. The Yellowstone hotspot is a volcanic hotspot in the United States responsible for large scale volcanism in Idaho, Montana, Nevada, Oregon, and Wyoming, formed as the North American tectonic plate moved over it. Magma comes mainly from two places where it is formed, (1) in the asthenosphere and (2) in the base of the crust above subducting lithosphere at a convergent plate boundary. Inner core is the very center of the Earth. Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic.Igneous rock is formed through the cooling and solidification of magma or lava.. Igneous rocks constitute one of the three principal classes of rocks, the others being metamorphic and sedimentary. The upper limit of metamorphism occurs at the pressure and temperature of wet partial melting of the rock in question. Outer core is a liquid layer below the mantle. True | False 9. And, like felsic magma, it is thick and jelly-like. Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). Melting of crustal sources yields more siliceous magmas. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.Typically, the melting is caused by There are three major types of magma. It is a high-temperature magma (1,200 C [about 2,200 F]) characterized by flowing lava, and it is made up of about 4555 percent silica (SiO 2) by weight.In contrast, the temperature of rhyolitic (or felsic) magma is much lower (750850 C [about 1,4001,560 F]), Silicic ones have lower temperatures and high viscosity. Geological studies of the Moon are based on a combination of Earth-based telescope observations, measurements from orbiting spacecraft, lunar samples, and geophysical data. Upper aesthenosphere: magma; Lower aesthenosphere; Lower mantle; The Earth's core is made of solid iron and nickel, and is at about 50006000 C. Learn more about the Mafic vs. Felsic geological classification through this ScienceStruck article. Pressure and composition are the most important parameters. Exercise 3.4 Porphyritic Minerals. which is about the temperature of the photosphere of the Sun. Basalt (UK: / b s l t,-l t /; US: / b s l t, b e s l t /) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.More than 90% of all volcanic rock on Earth is basalt. lava, magma (molten rock) emerging as a liquid onto Earths surface. If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture. Volatiles in a magma with a low viscosity, generally mafic with a lower silica content, tend to vent and can give rise to a lava fountain. Igneous rocks. The amount of melt produced depends only on the temperature of the mantle as it rises. [citation needed] Higher SiO 2 (silica) content magmas have higher viscosity than lower SiO 2 content magmas results in mafic/basaltic magmas. igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. Olivine also occurs in high-temperature metamorphic rocks, lunar basalts, and There are three main factors that affect the dispersion of volatiles in magma: confining pressure, composition of magma, temperature of magma. In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth.Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld This results in higher gas content and viscosity. 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