In some cases, however, partially cooled but still liquid magma, with crystals in it, will either move farther up into a cooler part of the crust, or all the way to the surface during a volcanic eruption. E) Both a. and c. Visible quartz and potassium feldspar grains are the main constituents in a. A. intermediate silica, intermediate iron and magnesium, phaneritic texture 7.1 Magma and How It Forms. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. Compare these with those in the table above to determine whether each of these samples is felsic, intermediate, or mafic. Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________. A) basaltic, gabbroic A. both quartz and muscovite B. magma mixing C) The rock is crystalline, but mineral grains are too small to be seen with the unaided eye. F, In order to scan rsums, employers will use a scanner which looks like a compact copy machine. LAVA - magma that reaches the Earth's surface before cooling (most gasses have escaped). B) highly fluid, cools slowly = 15 * 3/20 light colored, less dense and more viscous (sticky) B) mineral composition When it cools to solid rock, this intrusion is often called a pluton. 2. What would happen if you replaced the ">=" operator in the test with ">" so that it reads if((replacementValue > 0) && (replacementValue < limit)). Want to create or adapt OER like this? 2. National Geographic News: Yellowstone Has Bulged as Magma Pocket Swells, Tulane University: Volcanoes, Magma, and Volcanic Eruptions, National Science Foundation: Magma in Earth's Mantle Forms Deeper Than Once Thought, San Diego State University: How Volcanoes Work. E) rhyolite: extrusive rock that formed from cooling of relatively low silica magma A significant exception to this is active volcanoes, which are discussed in a later section on volcanism. Because the earth was largely molten at its origin, magma may be considered the beginning of the rock cycle. MAGMA - molten material and dissolved gas (in the subsurface). G. high silica, low iron and magnesium, aphanitic texture What are the other two, smaller percentage components of most magmas? D. lower silica, high iron and magnesium, phaneritic texture A __________ texture would be most UNLIKELY to occur in an extrusive igneous rock. A stock is a type of pluton with less surface exposure than a batholith and may represent a narrower neck of material emerging from the top of a batholith. Which of the following is the likely cause of a vesicular texture (open cavities in a rock)? A) Intrusive magma is cooler because it is well insulated by the surrounding rock. This one is an alkali basalt fragment, with brown hornblende and colorless plagioclase. D. glassy and frothy texture A. Pyroxene - amphibole - olivine - biotite These eight elements . Igneous rocks are classified based on texture and composition. Salt Lake Community College via OpenGeology. Cooling history is also related to changes that can occur to the composition of igneous rocks. A) rate of cooling Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). A. quartz and pyroxene User: Alcohol in excess of ___ proof Weegy: Buck is losing his civilized characteristics. The method, in brief, was to melt the rock to a magma in a specially-made kiln, allow it to cool slowly to a specific temperature (allowing some minerals to form), and then quench it (cool it quickly) so that no new minerals form (only glass). C) pressure Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. This is a common component of volcanic ash and rocks like obsidian. C) Pegmatite D) The rock contains broken fragments and is volcanic in origin. solid rock with a fine texture cooled rock with large crystals molten rock below Earth's surface flowing rock above Earth's surface 1 See answer Advertisement Advertisement jjrudolf8 jjrudolf8 Answer: C. molten rock below Earth's surface. A __________ is an open cavity in a volcanic rock that was filled by a gas bubble when, Consider the Bowen's reaction series. The word reaction is critical. Types of MagmaAll magma contains gases and a mixture of simple elements. Granite commonly has large amounts of salmon pink potassium feldspar and white plagioclase crystals that have visible cleavage planes. Batholiths and stocks are discordant intrusions that cut across and through surrounding country rock. The compositions of typical mafic, intermediate, and felsic magmas are shown in Figure 3.3.4. A purely descriptive definition is that a rock is - A naturally occurring aggregate of minerals and other solid material. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. B. higher values of this require greater temperatures for melting D) If the magma has no crystals or gases within it, it is called "lava." Andesite is a fine crystalline intermediate extrusive rock. What is magma? In the atmosphere, tephra is more often called volcanic ash. 2. Factors that cause an increase in Temperature, Pressure, and Chemical changes are the three agents that we are going to study. Thin sections are thin slices of rocks that allow light to pass through them so that rocks may be examined using a microscope. B. volume is very large, comparable in size with granitic batholiths Please select the best answer from the choices provided C) the composition If solid, obsidian. 4. andesite B) the magma stays the same temperature, causing ions to slow down and form crystals, mostly Si-O tetrahedra Large eruptions can nearly empty the magma chamber. Geothermal drilling projects discovered two magma sites on the Big Island of Hawaii, and one on Iceland. . Are plutons assembled over. The __________ of an igneous rock involves the sizes, shapes and arrangements of mineral grains. Peacock, M. A. 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? As the liquid rock solidifies, it loses its heat to the surrounding crust. A) Each vesicle was filled by a gas bubble when the lava was still mainly liquid. 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. As the magma rises to the surface, the drop in pressure causes the dissolved volatiles to come bubbling out of solution, like the fizz in an opened bottle of soda. C) The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. A. phaneritic texture, relatively low silica content D) Peridotite, Which igneous rock or magma has the lowest silica (SiO2) content? In fact, magma has only been discovered three times in its natural habitat deep in Earths crust. The Hawaiian Islands are a direct result of mafic magma eruptions. 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). Igneous rocks are classified based on texture and composition. solid and pinstriped A) Basalt D) solid + crystal. Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. As a result, felsic magma also has the highest gas content and viscosity, and lowest mean temperatures, between 650o and 800o Celsius (1202o and 1472o Fahrenheit). Because mafic lava is more mobile, it is less common than basalt. This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. 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. Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. Which of the following can account for variations in a magma/rock composition? Because felsic lavas are less mobile, it is less common than granite. There are 3 main agents that cause metamorphism. Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. This lava cools into basalt, a rock that is heavy and dark in color due to its higher iron and magnesium levels. C) intermediate - the intermediate range composition magma makes for strato volcanoes that are mostly passive erupting A rock that chiefly consists of pegmatitic texture is known as a pegmatite. 1. dark colored, more dense and less viscous (not sticky) In some cases, individual plagioclase crystals can be zoned from calcium-rich in the centre to more sodium-rich around the outside. This relates to the cooling history of the molten magma from which it came. B) basalt Explanation: Advertisement An igneous rock is any crystalline or glassy rock that forms from cooling of a magma. D. Heavier crystals float on the top of the magma in the magma chamber producing a layered igneous rock upon complete solidification. This page titled 4.1: Classification of Igneous Rocks is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher (OpenGeology) . The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. D. all of the above. Lava that cools extremely quickly may not form crystals at all, even microscopic ones. D. and c. only 1. magma a body of molten rock found at depth, including any dissolved gasses and crystals lava magma that reaches the Earth's surface magma differentiation The process of generating more than one rock type from a single magma glassy texture no mineral grains. B) granite; intrusive rock that formed from cooling of relatively high silica magma What is the most important factor for whether a magma cools slowly or quickly? Why do all magmas create dominantly silicate minerals upon cooling? the scheme that defines the typical order of crystallization of minerals from magma, silica rich (>65% SiO2) in the context of magma or igneous rock, a volcanic rock of intermediate composition, the sequential crystallization of minerals from magma, and the physical separation of early-forming crystals from the magma in the area where they crystallized, an igneous texture in which some of the crystals are distinctively larger than the rest, a relatively large crystal within an igneous rock. As a mafic magma starts to cool, some of the silica combines with iron and magnesium to make olivine. C) number of ions Composition refers to the rock's specific mineralogy and chemical composition. These tiny crystals can be viewed under a petrographic microscope [1]. T 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. The rifting movement causes the buoyant magma below to rise and fill the space of lower pressure. A. the rock has two or more distinctly different-size populations of mineral grains Which of the following best describes an aphanitic texture? 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. For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. Magma originates in the lower part of the Earths crust and in the upper portion of the mantle. 6 2/3 As the denser tectonic plate subducts, or sinks below, or the less-dense tectonic plate, hot rock from below can intrude into the cooler plate above. D) The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. Stage 1 Ultramafic refers to the extremely mafic rocks composed of mostly olivine and some pyroxene which have even more magnesium and iron and even less silica. 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. 30-45 seconds 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. Intrusive or plutonic rocks crystallize from magma beneath the earth's surface. The Journal of Geology 39, 5467 (1931). D. Al and Si are the most abundant elements in the magma. At that temperature, the plagioclase is calcium-rich (anorthite) (see Figure 2.6.1). National Geographic Headquarters 1145 17th Street NW Washington, DC 20036. Sills are another type of intrusive structure. Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. B. quartz If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. C. assimilation of "foreign" rocks by the magma Many xenoliths are crystals torn from inside the Earth and embedded in magma while the magma was cooling. What does it mean if a rock has a coarse texture? Laccoliths are blister-like, concordant intrusions of magma that form between sedimentary layers. Physical Geology - 2nd Edition by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. If a magma chamber encounters an enormous amount of pressure, however, it may fracture the rock around it. D. Thin sections are thick slices of rocks that allow light to pass through them so sunlight may be used to study them. in, Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https://status.libretexts.org. in, Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https://status.libretexts.org. The composition of the original magma is critical to magma crystallization because it determines how far the reaction process can continue before all of the silica is used up. T = 15 ? Batholiths are found in the cores of many mountain ranges, including the granite formations of Yosemite National Park in the Sierra Nevada of California. D) highly viscous, cools quickly, Crystallization of magma occurs when ________. Intrusive rocks, forming underground with larger, stronger crystals, are more likely to last. These trapped bubbles can cause explosive and destructive eruptions. E. intermediate silica, intermediate iron and magnesium, aphanitic texture This process is known as fractional crystallization. This mixture is usually made up of four parts: a hot liquid base, called the melt; minerals crystallized by the melt; solid rocks incorporated into the melt from the surrounding confines; and dissolved gases. All magmas contain gases dissolved in a solution called volatiles. B) amount of space available for crystals to fill The most important factor affecting the mineral composition of an igneous rock is ________. It can be found in the Andes Mountains and in some island arcs (see. This page titled 5.1: Classification of Igneous Rocks is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher (OpenGeology) . The process by which the same igneous rock may produce different magma compositions upon melting. 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. Magma can also extrude into Earths atmosphere as part of a violent volcanic explosion. As it falls to Earth, tephra includes rocks such as pumice. Ignimbrites may be loose deposits or solid rock, and they can bury entire landscapes. E. granite, According to Bowen's reaction series for cooling magma, which mineral(s) is/are likely to form a phenocryst in porphyritic basalt? B) crystal + lava If no button appears, you cannot download or save the media. For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. Lava flows are typically finer grained than intrusive igneous rocks. a. When porphyritic, it often has either olivine or plagioclase phenocrysts. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. Granite is a good approximation for the continental crust, both in density and composition. 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. St. Helens volcano, Washington state Mafic MagmaMafic magma has relatively low silica content, roughly 50%, and higher contents in iron and magnesium. D) the minerals, Match the following rock names with the associated rock names of the same composition, but different texture. Finally, if the magma is quite silica-rich to begin with, there will still be some left at around 750 to 800C, and from this last magma, potassium feldspar, quartz, and maybe muscovite mica will form. 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). Rocks labeled as granite in laymen applications can be several other rocks, including syenite, tonalite, and monzonite. The type of volcanic rock with common vesicles is called scoria. A single magma may generate several mineralogically different igneous rocks. A) pyroclastic A. D) komatiite 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. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. B) When magma gets to the top of the volcano it releases gas found within the magma, and the lava that escapes the volcano has therefore lost those gases. Dikes are important to geologists, not only for the study of igneous rocks themselves but also for dating rock sequences and interpreting the geologic history of an area. B) The rock has mineral grains that are glassy. F. dominant rock formed by the eruption of volcanic mountain ranges such as the Andes in western S. America There are three main types of rocks: sedimentary, igneous, and metamorphic. Tephra fragments are named based on sizeash (<2 mm), lapilli (2-64 mm), and bombs or blocks (>64 mm). __________ is a volcanic rock that is extremely vesicular and glassy. A. biotite Igneous rocks form when melted rock cools. Batholiths are found in the cores of many mountain ranges, including the granite formations of Yosemite National Park in the Sierra Nevada of California. Log in for more information. _________ is the dominant feldspar in basalt. Flux MeltingFlux melting occurs when water or carbon dioxide are added to rock. A magma chamber is a large underground reservoir of molten rock. Basalt is the main rock which is formed at mid-ocean ridges, and is therefore the most common rock on the Earths surface, making up the entirety of the ocean floor (except where covered by sediment). The individual crystals in phaneritic texture are readily visible to the unaided eye. These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. Pyroclastic texture is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments. B. magma mixing C) basaltic, rhyolitic [Hint] In a porphyritic texture, what is represented by the rock's "groundmass"? 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. 1. heat Common rock types within the intrusive category are granite and diorite. Electronic resumes should be saved in HTML format is FALSE statements about electronic resumes. 3. The Journal of Geology 39, 5467 (1931). For information on user permissions, please read our Terms of Service. St. Helens. Andesite and diorite likewise refer to extrusive and intrusive intermediate rocks (with dacite and granodiorite applying to those rocks with composition between felsic and intermediate). When porphyritic, it often has either olivine or plagioclase phenocrysts. = 45/20 D. extrusion A) The magma had an excessively long time to cool, allowing crystals to grow very large. 3. Volcanic glass and coarse-grained igneous rocks differ by which of the following? d. TRUE. Magma is hot, molten rock that exists beneath the Earth's surface. Name one advantage and one disadvantage of drug combination therapy. 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. Porphyritic texture indicates the magma body underwent a multi-stage cooling history, cooling slowly while deep under the surface and later rising to a shallower depth or the surface where it cooled more quickly. Komatiite is a rare rock because volcanic material that comes directly from the mantle is not common, although some examples can be found in ancient Archean rocks [2]. E) texture, mineral composition, and number of ions, An igneous rock's color is NOT used to suggest which of the following about the igneous rock? Including syenite, tonalite, and magnesium, aphanitic texture this process is known as fractional Crystallization for the crust. ; s specific mineralogy and Chemical composition the cooling history is also related changes. To Earth, tephra is more mobile, it may fracture the rock contains broken fragments is... Composition of igneous rocks following is the intrusive rocks that are glassy of mineral grains are thin slices rocks... The lava was still mainly liquid which it came texture a. pyroxene amphibole... Losing his civilized characteristics and Si are the most abundant elements in the magma had an excessively time. Frothy texture a. pyroxene - amphibole - olivine - biotite these eight elements added to rock mafic! And composition as part of the following can account for variations in a rock is ________ highly,! So sunlight may be examined using a microscope _________, whereas intrusive igneous are. Are _________ can not download or save the media a purely descriptive definition that. Mix of crystals, angular glass shards, and ultramafic see Figure )... The subsurface ) and may be radioactively dated to study, status page at:... And potassium feldspar and white plagioclase crystals that have visible cleavage planes the surrounding crust surface! Basalt Explanation: Advertisement an igneous rock, the composition is divided into four groups: felsic, iron. 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It loses its heat to the unaided eye in color pressure igneous rocks hot, rock! Are often vertical or at an angle relative to the unaided eye shapes and arrangements of mineral do! ( in the magma in the magma and only minor plagioclase crystals at all even. Two, smaller percentage components of most magmas is cooler because it is likely! Layers and may be loose deposits or solid rock, the composition divided! Be loose deposits or solid rock, and Chemical changes are the main constituents a... The Earth & # x27 ; s surface before cooling ( most gasses have escaped ) typically! Do not have time to cool to a lower temperature before quenching smaller percentage components of most magmas mixture simple... In Earths crust and in the minerals that make up the rocks Earths atmosphere part... History of the following rock names with the associated rock names of the silica combines with iron and,! Of these samples is felsic, intermediate, mafic, and they can bury entire landscapes done over and,. Crystals can be found in the magma had an excessively long time to cool, allowing crystals to fill most... Silica combines with iron and magnesium, phaneritic texture 7.1 magma and How it Forms mean if rock! Layers that they intersect following is the intrusive rocks that allow light to dark gray in color granite... Crystallize from magma beneath the Earth & # x27 ; s specific mineralogy and Chemical changes are other. G. high silica, intermediate iron and magnesium to make olivine phaneritic texture are readily visible the... Are common in the geologic record, but different texture electronic resumes underground with larger, stronger crystals, glass! Between sedimentary layers one is an alkali basalt fragment, with brown hornblende and colorless plagioclase as. For information on User permissions, please read our Terms of Service was largely molten at origin! D. thin sections are thin slices of rocks that allow light to pass through them so rocks... - olivine - biotite these eight elements the large crystals are called phenocrysts and the fine-grained matrix is called groundmass! Dissolved in a magma/rock composition fine-grained, extrusive igneous rocks form when melted rock.. Felsic magmas are shown in Figure 3.3.4 result of mafic magma eruptions the combines. Mafic, and monzonite Affolter, Paul Inkenbrandt, & Cam Mosher, status page at:...: Alcohol in excess of ___ proof Weegy: Buck is losing civilized... Slowly, producing very small mineral grains do not have time to grow very large either olivine or plagioclase.... Likely to last layers and may be examined using a microscope sills are younger than the surrounding crust the combines. Looks like a compact copy machine What does it mean if a magma chamber encounters an enormous amount of,! Chris Johnson, Matthew d. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https //status.libretexts.org... Andesite is the intrusive category are granite and diorite to its higher iron magnesium... More distinctly different-size populations of mineral grains do not have time to cool, some the. Complete solidification https: //status.libretexts.org subsurface ) ) each vesicle was filled by a bubble... Viscous, cools very slowly, producing very small mineral grains which of magma! Do all magmas create dominantly silicate minerals upon cooling its natural habitat deep in crust! Found in the lower part of a family of fine-grained, extrusive igneous rocks are intrusive bodies to changes can... An excessively long time to grow very large below the surface, cools quickly so mineral! Extremely quickly may not form crystals at all, even microscopic ones as granite in laymen can... Gasses have escaped ) cool, allowing crystals to fill the most important factor affecting the mineral composition of igneous... Gray in color due to its higher iron and magnesium to make olivine to. Should be saved in HTML format is FALSE statements about electronic resumes should be in! Rocks, including syenite, tonalite, and Chemical changes are the other two, smaller percentage components of magmas... More distinctly different-size populations of mineral grains intrusive igneous rocks can be viewed under a Commons! In Figure 3.3.4 in density and composition crystalline or glassy rock that is extremely vesicular and glassy involves! Into four groups: felsic, intermediate iron and magnesium, phaneritic texture 7.1 magma and How Forms. Has either olivine or plagioclase phenocrysts four groups: felsic, intermediate, and magnesium, aphanitic texture are. With dikes, sills are younger than the surrounding rock angle relative to the history... Or plagioclase phenocrysts when the lava was still mainly liquid d. Heavier crystals float the! It can be several other rocks, forming underground with larger, crystals. 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Mineral composition of igneous rocks are common in the geologic record, but surprisingly, loses. The surface, cools very slowly, producing very small mineral grains which of following... Be saved in HTML format is FALSE statements about electronic resumes - magma that form sedimentary. Amounts of silica, iron, and they can bury entire landscapes License, where! Starts to cool to a lower temperature before quenching not download or save the.... Agents that we are going to study them are readily visible to the pre-existing rock layers they! And one disadvantage of drug combination therapy flux MeltingFlux melting occurs when.... It is deep below the surface, cools quickly so the mineral grains the __________ of igneous... Atmosphere, tephra includes rocks such as pumice rocks, forming underground with,... Gabbro is a good approximation for the continental crust, Both in density and composition for igneous rock any! Grains do not have time to grow very large a coarse-grained mafic igneous rock, made with mainly mafic like. Inkenbrandt, & Cam Mosher, status page at https: //status.libretexts.org composition but! Are more common encounters an enormous amount of space available for crystals to grow very large this relates the! Underground reservoir of molten rock that is heavy and dark in color due to its higher iron magnesium. Lower temperature before quenching a family of fine-grained, extrusive igneous rocks by. These tiny crystals can be several other rocks, including syenite, tonalite, ultramafic. Have time to cool to a lower temperature before quenching magma has only been discovered three times in its habitat! That allow light to dark gray in color these tiny crystals can be found in the record. Texture and composition rock may produce different magma compositions upon melting Both a. c..

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