Arndt, N. T. Chapter 1 Archean Komatiites. C. assimilation of "foreign" rocks by the magma F. dominant rock formed by the eruption of volcanic mountain ranges such as the Andes in western S. America Intrusive rocks, forming underground with larger, stronger crystals, are more likely to last. The Journal of Geology 39, 5467 (1931). Normally, geothermal energy is created by pumping water into hot volcanic bedrock, creating steam that is then harnessed to generate electricity. Much like hot fudge being poured over cold ice cream, this transfer of heat is able to melt the surrounding rock (the ice cream) into magma. C) rate of cooling G. both olivine and pyroxene, Which two minerals are characteristic of lower crystallization temperatures, and are absent in basalt and gabbro? If the fragments accumulate while still hot, the heat may deform the crystals and weld the mass together, forming a welded tuff. 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 partially molten rock material. D. andesite A significant exception to this is active volcanoes, which are discussed in a later section on volcanism. When lava is extruded onto the surface, or intruded into shallow fissures near the surface and cools, the resulting igneous rock is called extrusive or volcanic. Most magma chambers sit far beneath the surface of the Earth. Match the igneous rock texture and its appropriate description. 3. phaneritic Young, emerging subvolcanic intrusion cutting through older one, Xenolith (solid rock of high melting temperature which has been transported within the magma from deep below) or roof pendant (fragment of the roof of the magma chamber that has detached from the roof and sunk into the melt), Contact metamorphism in the country rock adjacent to the magma chamber (caused by the heat of the magma), Uplift at the surface due to laccolith emplacement in the near sub-ground, Active magma chamber (called pluton when cooled and entirely crystallized; a batholith is a large rock body composed of several plutonic intrusions), Old pegmatite (late-magmatic dyke formed by aggressive and highly mobile residual melts of a magma chamber). E. pyroxene, Which one of the following rock types is most likely to contain calcium-rich feldspar? Lava flows are typically finer grained than intrusive igneous rocks. light colored, less dense and more viscous (sticky) C) Mafic is hard rock, felsic is soft rock. D. consist of very coarse grained crystals of potassium feldspar, muscovite and quartz The __________ of an igneous rock involves the sizes, shapes and arrangements of mineral grains. A. Pyroxene - amphibole - olivine - biotite TRUE. D) The rock contains broken fragments and is volcanic in origin. B. 1996 - 2023 National Geographic Society. Salt Lake Community College via OpenGeology. F, In order to scan rsums, employers will use a scanner which looks like a compact copy machine. At about the point where pyroxene begins to crystallize, plagioclase feldspar also begins to crystallize. Felsic magmas, on the other hand, have much more SiO2 (65% to 75%) and Na2O + K2O (around 10%) and much less FeO and MgO plus CaO (about 5%). D) gabbroic, What composition magma is beneath the Mt. D) the minerals, Match the following rock names with the associated rock names of the same composition, but different texture. A) rate of cooling 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. C) Both of these. [Hint] What is magma? 1. diorite and gabbro A) Intrusive magma is cooler because it is well insulated by the surrounding rock. C) Pressure of the environment - higher P = slower magma cooling. A magma chamber is a large underground reservoir of molten rock. The processes by which a diapir intrudes into the surrounding native or country rock are not well understood and are the subject of ongoing geological inquiry [3]. Rock formed from large deposits of tephra fragments is called tuff. A rock that chiefly consists of pegmatitic texture is known as a pegmatite. The Weegy: A modal verb (also modal, modal auxiliary verb, modal auxiliary) is a type of auxiliary verb that is used to WINDOWPANE is the live-streaming app for sharing your life as it happens, without filters, editing, or anything fake. Legal. B) considered "plutonic" rocks because they form from magma beneath the surface; considered "volcanic" because they form from lava erupted from a volcano. D. muscovite and quartz, According to Bowen's reaction series, which is the proper sequence of ferromagnesian silicate minerals crystallizing from a cooling magma? False, Applications and Investigations In Earth Science, Dennis G. Tasa, Edward J. Tarbuck, Frederick K. Lutgens, Charles C. Plummer, Diane Carlson, Lisa Hammersley. Stage 2 Visible quartz and potassium feldspar grains are the main constituents in a. In 1912, Norman Levi Bowenhe joined the Carnegie Institution in Washington, D.C., where he carried out groundbreaking experimental research into the processes of cooling magmas. These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. The type of volcanic rock with common vesicles is called scoria. Rocks that solidify from lava flows are typically finer grained than those that crystallize intrusively. B) The magma was rich in volatiles (like water) which aided in fast crystallization of large, but few numbers of crystals. This relates to the cooling history of the molten magma from which it came. __________ is a volcanic rock that is extremely vesicular and glassy. All rights reserved. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Extrusive rocks, because of their small crystals and glass, are less durable. Typical felsic rocks are granite and rhyolite (Figure 3.3.5). A. chemical bonds melt In either of these situations, the magma that has moved toward the surface is likely to cool much faster than it did within the magma chamber, and the rest of the rock will have a finer crystalline texture. For information on user permissions, please read our Terms of Service. D) rhyolitic, What type of composition would result in a magma if basaltic and granitic composition magma were mixed completely at a 1 to 3 ratio? How much is a steak that is 3 pounds at $3.85 per pound. The path of rising magma is called a diapir. Composition refers to the rocks specific mineralogy and chemical composition. Note that, unlike Figure 3.2.1, these compositions are expressed in terms of oxides (e.g., Al2O3 rather than just Al). Igneous rocks form when melted rock cools. Magma forms under Earth's surface at about 800 to 1300C in the crust or mantle and erupts on Earth's surface as lava.When magma or lava cools, it solidifies by crystallization in which minerals grow within the magma or lava. Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. E) basalt, Which of the following rocks is likely to have the most quartz within it and why? C) light colored, less dense and more viscous (sticky); D) considered "volcanic" rocks because they form from lava extruded at the surface; considered "plutonic" rocks because they form from magma beneath the surface. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. Note that these 8 elements make up about 99 percent of the Earth's crust. Young, emerging subvolcanic intrusion cutting through older one, Xenolith (solid rock of high melting temperature which has been transported within the magma from deep below) or roof pendant (fragment of the roof of the magma chamber that has detached from the roof and sunk into the melt), Contact metamorphism in the country rock adjacent to the magma chamber (caused by the heat of the magma), Uplift at the surface due to laccolith emplacement in the near sub-ground, Active magma chamber (called pluton when cooled and entirely crystallized; a batholith is a large rock body composed of several plutonic intrusions), Old pegmatite (late-magmatic dyke formed by aggressive and highly mobile residual melts of a magma chamber). Basalt is a fine-grained mafic igneous rock. What is the most important factor for whether a magma cools slowly or quickly? In some cases, extrusive lava cools so rapidly it does not develop crystals at all. 3. extrusive igneous rock A. a decrease in the confining pressure (decompression) Why are thin sections of rocks used to study igneous rocks? Magmas derived from crustal material are dominated by oxygen, silicon, aluminum, sodium, and potassium. C) highly fluid, cools quickly D) Peridotite, Which igneous rock or magma has the lowest silica (SiO2) content? This is a common component of volcanic ash and rocks like obsidian. When you reach out to him or her, you will need the page title, URL, and the date you accessed the resource. As the temperature drops, and providing that there is sodium left in the magma, the plagioclase that forms is a more sodium-rich variety. D) chemical composition of the magma or lava. D) The glass is formed mostly when lava cools in contact with water whereas phaneritic rocks cool deep beneath the surface. This reduction in overlying pressure, or decompression, enables the mantle rock to melt and form magma. A. convergent plate boundaries A) the magma heats up and ions in crystals break their bonds due to expansion and Si and O ion vibration As the liquid rock solidifies, it loses its heat to the surrounding crust. B) Mafic is a magma/rock that is rich in Fe and Mg, whereas felsic refers to that which is rich in feldspar and silica (quartz) B) the first crystals to form when the magma was in the magma chamber An igneous rock with large crystals embedded in a matrix of much finer crystals is indicative of a two-stage cooling process, and the texture is porphyritic (Figure 3.3.7). Legal. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Which of the following can account for variations in a magma/rock composition? If the magma has a low viscosity (i.e., its runny)which is likely if it is maficthe crystals that form early, such as olivine (Figure 3.3.6a), may slowly settle toward the bottom of the magma chamber (Figure 3.3.6b). B) granodioritic Earth Science, Geology, Geography, Physical Geography. D) komatiite Arndt, N. T. Chapter 1 Archean Komatiites. 5. pumice The rate of cooling determines the rock's texture, or size of the mineral's crystals. Physical Geology - 2nd Edition by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. Magma can also extrude into Earths atmosphere as part of a violent volcanic explosion. An igneous rock with large crystals embedded in a matrix of finer crystals is indicative of a two-stage cooling process, and the texture is porphyritic (Figure 3.15). In comparison, one single wind turbine generates between 1 to 3 megawatts. Comments C) andesitic As a magma cools below 1300C, minerals start to crystallize within it. 1. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. This one is an alkali basalt fragment, with brown hornblende and colorless plagioclase. Andesite is a fine crystalline intermediate extrusive rock. = 15 * 3/20 Decompression melting often occurs at divergent boundaries, where tectonic plates separate. That magma body at depth is normally totally encased by solid rock (perhaps with a zone of broken and partly melted rock measuring a few meters thick; depends on the magma and the host rock and how much time has passed), and that solid rock would be the floor, walls, and ceiling to the magma body. A) chemical composition of the magma or lava Nature rarely has sharp boundaries and the classification and naming of rocks often impose what appears to be sharp boundary names onto a continuous spectrum. This non-crystalline material is not classified as minerals but as volcanic glass. These trapped bubbles can cause explosive and destructive eruptions. Figure 4.1.1. molten rock below Earths surface What is magma? LAVA - magma that reaches the Earth's surface before cooling (most gasses have escaped). A purely descriptive definition is that a rock is - A naturally occurring aggregate of minerals and other solid material. If any melting takes place, crystal settling will make the magma at the bottom of the chamber more mafic than it was to begin with (Figure 3.3.6c). Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. E. often contain diamonds, sapphires and rubies, Which one of the following rocks is the primary constituent of the upper layers of the oceanic crust? An active volcano always has a magma chamber beneath the cone. b. The rifting movement causes the buoyant magma below to rise and fill the space of lower pressure. D. plate tectonics, Match the appropriate term associated with the production of magma to its best description. Andesite is a fine crystalline intermediate extrusive rock. 3. diorite 1. Whenever an individual stops drinking, the BAL will ________________. The cracks, called fissures or vents, are tell-tale signs of a volcano. An eruption reduces the pressure inside the magma chamber. To give an example of how large these crystals can get, transparent cleavage sheets of pegmatitic muscovite mica were used as windows during the Middle Ages. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. D. muscovite A. phaneritic texture, relatively low silica content The gas bubbles become trapped in the solidifying lava to create a vesicular texture, with the holes specifically called vesicles. seated magma in the magma chamber ascend s due to buoyancy or any tectonic activity and intrudes into the country rock (host rock) or it may come out at the surface and solidify. A significant exception to this is active volcanoes, which are discussed in a later section on volcanism. It has also been proposed that diapirs are not a real phenomenon, but just a series of dikes that blend into each other. C. Thin sections are thin slices of rocks that block light from passing through them so that rocks may be studied using a magnifying lens. Thin sections are thin slices of rocks that allow light to pass through them so that rocks may be examined using a microscope. Arndt, N. T. Chapter 1 Archean Komatiites. B) granodioritic This process is known as fractional crystallization. A. peridotite Inflammation of the lymph vessels is known as________. 7. obsidian, Which of the following is characteristic of pegmatites? The individual crystals in phaneritic texture are readily visible to the unaided eye. C) basaltic, rhyolitic FALSE. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. Each of these rocks are formed by physical changessuch as melting, cooling, eroding, compacting, or deforming that are part of the rock cycle. The slow cooling process allows crystals to grow large, giving the intrusive igneous rock a coarse-grained or phaneritic texture. Because mafic lava is more mobile, it is less common than basalt. Peacock, M. A. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. 1. andesite D. ions vibrate so much that the vibrating breaks some of the chemical bonds, What process (or processes) can aid in generating magma from solid rock? 1. A single magma may generate several mineralogically different igneous rocks. For example, it is not known what happens to the pre-existing country rock as the diapir intrudes. Composition refers to a rocks chemical and mineral make-up. National Geographic Headquarters 1145 17th Street NW Washington, DC 20036. A __________ is an open cavity in a volcanic rock that was filled by a gas bubble when, Consider the Bowen's reaction series. This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. . Much like intermediate magma, felsic magma may be most commonly found at convergent plate boundaries where transfer of heat and flux melting create large stratovolcanoes. As the temperature drops, and assuming that some silica remains in the magma, the olivine crystals will react (combine) with some of the silica in the magma to form pyroxene. The Rights Holder for media is the person or group credited. What does it mean if a rock has a coarse texture? This relates to the cooling history of the molten magma from which it came. These eight elements . F. lower silica, high iron and magnesium, aphanitic texture Igneous rocks contain information about how they originate. Examples of rhyolite include several lava flows in Yellowstone National Park and the altered rhyolite that makes up the Grand Canyon of the Yellowstone. Diorite is a coarse-crystalline intermediate intrusive igneous rock. C. the introduction of volatiles (e.g., water) Stage 3, Instead of having to know HTML code, most Web sites will have templates that make creating Web rsums easy. This relates to the cooling history of the molten magma from which it came. The __________ of an igneous rock involves the mineral content, and/or refers to the magma from which it solidified. A) granite The solid parts, called tephra, settle back to earth and cool into rocks with pyroclastic textures. This heat makes magma a very fluid and dynamic substance, able to create new landforms and engage physical and chemical transformations in a variety of different environments. Gabbro is a major component of the lower oceanic crust. A) highly viscous, cools slowly For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. Which are definitions of "mafic" and "felsic"? E. intermediate silica, intermediate iron and magnesium, aphanitic texture Plutons can have irregular shapes, but can often be somewhat round. Electronic resumes should be saved in HTML format is FALSE statements about electronic resumes. Mafic magmas have 45% to 55% SiO2, about 25% total of FeO and MgO plus CaO, and about 5% Na2O + K2O. Pyro, meaning fire, refers to the igneous source of the tephra and clastic refers to the rock fragments. C) The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. B. quartz in Developments in Precambrian Geology (ed. Granite: Granite is the intrusive equivalent of rhyolite but has a coarser texture. On page 14 of The Call of the Wild, what's meant by the phrase "The _____ is defined as to lose or give up hope that things will 15. A. Kilauea volcano, Hawaii They are typically more than 100 km2 in area, associated with subduction zones, and mostly felsic in composition. MAGMA - molten material and dissolved gas (in the subsurface). Which mineral would you expect to see as a, Which of the following igneous rocks exhibit aphanitic texture? If you have questions about licensing content on this page, please contact ngimagecollection@natgeo.com for more information and to obtain a license. D) peridotite, Most magmas are dominantly molten rock (a liquid called "melt"). Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates. 1. granite 3.5 Igneous Rocks Charlene Estrada. 20/3 These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. When porphyritic, it often has either olivine or plagioclase phenocrysts. She or he will best know the preferred format. Batholiths and stocks are discordant intrusions that cut across and through surrounding country rock. Basalt and gabbro are the extrusive and intrusive names for mafic igneous rocks, and peridotite is ultramafic, with komatiite as the fine-grained extrusive equivalent. Diorite is a coarse-crystalline intermediate intrusive igneous rock. C. granite Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). Mysterious MagmaMagma is usually studied as lava or igneous rock. Magma that has cooled into a solid is called igneous rock. Felsic MagmaFelsic magma has the highest silica content of all magma types, between 65-70%. A) The magma had an excessively long time to cool, allowing crystals to grow very large. Residual molten material expelled from igneous intrusions may form veins or masses containing very large crystals of minerals like feldspar, quartz, beryl, tourmaline, and mica. Explanation: Advertisement On the figure above, the top row has both plutonic and volcanic igneous rocks arranged in a continuous spectrum from felsic on the left to intermediate, mafic, and ultramafic toward the right. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. Are plutons assembled over. One theory is the overriding rock gets shouldered aside, displaced by the increased volume of magma. Composition refers to the rock's specific mineralogy and chemical composition. 30-45 seconds Dikes are therefore discordant intrusions, not following any layering that was present. B. Olivine - pyroxene - amphibole - biotite Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. D) the rock's density, The most important factor affecting the texture of an igneous rock is ________. When magma intrudes into a weakness like a crack or a fissure and solidifies, the resulting cross-cutting feature is called a dike (sometimes spelled dyke). Batholiths are found in the cores of many mountain ranges, including the granite formations of Yosemite National Park in the Sierra Nevada of California. A magma chamber is a large underground reservoir of molten rock. Magma Escape Routes Magma leaves the confines of the upper mantle and crust in two major ways: as an intrusion or as an extrusion. B) basaltic - very sticky magma makes for very passive (fluid) eruptions An intrusion can form features such as dikes and xenoliths. The resulting rock is called volcanic glass. When it cools to solid rock, this intrusion is often called a pluton. Gabbro is a major component of the lower oceanic crust. Thus, you can often figure out the relative order in which the minerals crystallized from the magma. K.C. Plutons can include dikes and xenoliths. They have textures or mineralogy different than the surrounding material, and so are generally easy to spot. Tephra fragments are named based on sizeash (<2 mm), lapilli (2-64 mm), and bombs or blocks (>64 mm). Its mean temperature ranges from 800o to 1000o Celsius (1472o to 1832o Fahrenheit). E. granite, According to Bowen's reaction series for cooling magma, which mineral(s) is/are likely to form a phenocryst in porphyritic basalt? Over millions of years, many magma chambers simply cool to form a pluton or large igneous intrusion. F) The presence or absence of volatiles (gases) - more gases = slower magma cooling. Book: An Introduction to Geology (Johnson, Affolter, Inkenbrandt, and Mosher), { "5.01:_Classification_of_Igneous_Rocks" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
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