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. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. Mafic rocks/magmas are ________, whereas felsic rocks/magmas are ________. 3. decompression melting Commonly even very felsic rocks will not have biotite or muscovite because they may not have enough aluminum or enough hydrogen to make the OH complexes that are necessary for mica minerals. 2. porphyritic andesite National Geographic Society is a 501 (c)(3) organization. B) The rock has mineral grains that are glassy. Visible quartz and potassium feldspar grains are the main constituents in a. B) dark colored, more dense and less viscous (not sticky); D. all of the above. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. C. heat expansion of the chemical bonds causes them to break Extrusive or volcanic rocks crystallize from lava at the earth's surface. D. a magnifying glass or microscope is needed to see individual mineral grains Sedimentary rocks are formed from pieces of other existing rock or organic material. A) chemical composition of the magma or lava Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates. A) diorite; intrusive rock that formed from the cooling of relatively intermediate silica magma Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________. What two factors determine what type of rock a magma will form?-One is the composition of the magma. It is the source of all igneous rock. B. mineral grains are roughly equal size and coarse enough to be seen without the aid of a microscope or magnifying lens It is poor in silica, in the 40% or less range. The different colors are unique minerals. What are the other two, smaller percentage components of most magmas? Laccoliths bulge upwards; a similar downward-bulging intrusion is called a lopolith. It is important to realize these groups do not have sharp boundaries in nature, but rather lie on a continuous spectrum with many transitional compositions and names that refer to specific quantities of minerals. When porphyritic, it often has either olivine or plagioclase phenocrysts. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. This process is known as fractional crystallization. A __________ texture would be most UNLIKELY to occur in an extrusive igneous rock. 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When it cools to solid rock, this intrusion is often called a pluton. A. Obsidian is a rock consisting of volcanic glass. D) chemical composition of the magma or lava. This relates to the cooling history of the molten magma from which it came. When many plutons merge together in an extensive single feature, it is called a batholith. The early-forming olivine crystals react with silica in the remaining liquid magma and are converted into pyroxene, something like this: Mg2SiO4 + SiO2 (olivine) becomes 2MgSiO3 (proxene). What would happen if you replaced the ">=" operator in the test with ">" so that it reads 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]. Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. Explanation: Advertisement This type of magma has a low gas content and low viscosity, or resistance to flow. For a volcano to erupt, it must have a source of magma. Granite is a good approximation for the continental crust, both in density and composition. = 15 * 3/20 MAGMA - molten material and dissolved gas (in the subsurface). Condie) 11, 1144 (Elsevier, 1994). Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. Typical felsic rocks are granite and rhyolite (Figure 3.3.5). A. consist of very large grains of quartz, olivine and pyroxene in relatively large bodies of former sedimentary rock Inflammation of the lymph vessels is known as________. G. high silica, low iron and magnesium, aphanitic texture Gabbro is a major component of the lower oceanic crust. 4. glassy. But most magma remains molten or partly molten beneath Earths surface. Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. Basalt is a fine-grained mafic igneous rock. Figure 3.3.1, 3.3.4, 3.3.5, 3.3.6, 3.3.7, 3.3.8: Steven Earle. Intermediate MagmaIntermediate magma has higher silica content (roughly 60%) than mafic magma. Granite is a course-crystalline felsic intrusive rock. It is commonly vesicular and aphanitic. F) Both c. and d. C. assimilation of "foreign" rocks by the magma Name one advantage and one disadvantage of drug combination therapy. D) Both a. and c. This creates magma in places where it originally maintained a solid structure. 1. aphanitic 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. 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. There are three main types of rocks: sedimentary, igneous, and metamorphic. Any interactives on this page can only be played while you are visiting our website. A. Kilauea volcano, Hawaii Andesitic rocks are often found at continental volcanic arcs, such as the Andes Mountains in South America, after which they are named. One theory is the overriding rock gets shouldered aside, displaced by the increased volume of magma. Dikes are therefore discordant intrusions, not following any layering that was present. Areas of lower pressure always have a lower melting point than areas of high pressure. Rhyolite is a fine-crystalline felsic extrusive rock. A) Pressure of the environment - lower P = slower magma cooling. This is a common component of volcanic ash and rocks like obsidian. A) granite The slow cooling process allows crystals to grow large, giving the intrusive igneous rock a coarse-grained or phaneritic texture. This relates to the cooling history of the molten magma from which it came. = 2 1/4. This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. The composition of magma depends on the rock it was formed from (by melting), and the conditions of that melting. It can be found in the Andes Mountains and in some island arcs (see. 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. Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. If a media asset is downloadable, a download button appears in the corner of the media viewer. Differences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways. Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. C) solid + melt The Journal of Geology 39, 5467 (1931). = 2 5/20 A. high levels are necessary for melting of rocks Types of MagmaAll magma contains gases and a mixture of simple elements. User: 3/4 16/9 Weegy: 3/4 ? C. Amphibole - pyroxene - biotite - olivine c. Common rock types within the intrusive category are granite and diorite. A) andesitic 30-45 seconds K.C. It erupts non-explosively and moves very quickly when it reaches Earths surface as lava. For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. 2. granite and granodiorite What does it mean if a rock has a coarse texture? These eruptions eject lava violently into the air, which cools into dacite and rhyolite rock. 7.1 Magma and How It Forms. D) the lava in the crystallizing magma chamber before eruption. Magma is molten rock below Earths surface. C. the lower crust Intrusive rocks, forming underground with larger, stronger crystals, are more likely to last. D. Heavier crystals float on the top of the magma in the magma chamber producing a layered igneous rock upon complete solidification. Physical Geology - 2nd Edition by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. A) The glass is formed mostly when lava cools in a volcano whereas phaneritic rocks cool at the surface. Magma Chamber In areas where temperature, pressure, and structural formation allow, magma can collect in magma chambers. a. Regardless, when a diapir cools, it forms a mass of intrusive rock called a pluton. 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. There are two reasons for this: one is that in the early analytical procedures, the results were always expressed that way, and the other is that all of these elements combine readily with oxygen to form oxides. B. volume is very large, comparable in size with granitic batholiths light colored, more dense and less viscous (not sticky), What type of composition would result in a magma if equal amounts of basaltic and granitic magma were mixed? 3. extrusive igneous rock If the magma cools slowly underground, the product will be gabbro; if it cools quickly at the surface, the product will be basalt (Figure 3.3.5). 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. Which of the following best describes an aphanitic texture? When porphyritic, it often has either olivine or plagioclase phenocrysts. A) the rock's texture A pluton is an intrusion of magma that wells up from below the surface. 3. Using Figure 3.3.8, predict what phenocrysts might be present where the magma cooled as far as line a in one case, and line b in another. 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%). If vesicular, pummus geothermal gradient In the atmosphere, tephra is more often called volcanic ash. This process transfers heat and creates magma. 2 minutes, Web rsums are posted to the Internet in HTML format. F) basalt; extrusive rock that formed from cooling of relatively low silica lava, Match the volcano with the appropriate rock formed by its eruption. B. magma mixing The environment in which an igneous rock solidified (extrusive, intrusive or otherwise) can be inferred best by which of the following? True Over millions of years, the magma in this subduction zone can create a series of active volcanoes known as a volcanic arc. D. lower silica, high iron and magnesium, phaneritic texture A) Mafic is a magma/rock that is rich in feldspar and silica (quartz), whereas felsic refers to that which is rich in Fe and Mg. This relates to the cooling history of the molten magma from which it came. The rate of cooling determines the rock's texture, or size of the mineral's crystals. Igneous rocks are classified based on texture and composition. Plutons can have irregular shapes, but can often be somewhat round. The word reaction is critical. B) mineral composition D. glassy and frothy texture 1. diorite and gabbro B) amount of space available for crystals to fill 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. Added 2/10/2022 11:11:08 PM This answer has been confirmed as correct and helpful. in, Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https://status.libretexts.org. A magma consists mostly of liquid rock matter, but may contain crystals of various minerals, and may contain a gas phase that may be dissolved in the liquid or may be present as a separate gas phase. Note that these 8 elements make up about 99 percent of the Earth's crust. C) andesitic The solid parts, called tephra, settle back to earth and cool into rocks with pyroclastic textures. D) If the magma has no crystals or gases within it, it is called "lava." Tephra fragments are named based on sizeash (<2 mm), lapilli (2-64 mm), and bombs or blocks (>64 mm). B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. 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? 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. 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. Because felsic lavas are less mobile, it is less common than granite. D. extrusion Laccoliths bulge upwards; a similar downward-bulging intrusion is called a lopolith. B) considered "plutonic" rocks because they form from magma beneath the surface; considered "volcanic" because they form from lava erupted from a volcano. This non-crystalline material is not classified as minerals but as volcanic glass. 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. Olivine - pyroxene - amphibole - biotite 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]. C) the magma in the magma chamber before eruption C) basalt; extrusive rock that formed from cooling of relatively high silica lava 6 2/3 D) komatiite E) rhyolite: extrusive rock that formed from cooling of relatively low silica magma C) The rock is crystalline, but mineral grains are too small to be seen with the unaided eye. 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. 16/9 = Weegy: Whenever an individual stops drinking, the BAL will decrease slowly. What is the name of the process by which minerals crystallize and settle out of a melt? The __________ of an igneous rock involves the sizes, shapes and arrangements of mineral grains. Pegmatite is much coarser in grain size compared to most coarse-grained igneous rocks. There are 3 main agents that cause metamorphism. An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. Igneous rocks constitute one of the three principal classes of rocks, the others being metamorphic and sedimentary. The individual crystals in phaneritic texture are readily visible to the unaided eye. Salt Lake Community College via OpenGeology. B. diorite Who was Bowen, and what is a reaction series? This results in a higher gas content and viscosity. It is commonly grey and porphyritic. A) Intrusive magma is cooler because it is well insulated by the surrounding rock. A. This reduction in overlying pressure, or decompression, enables the mantle rock to melt and form magma. 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). A. Si and O are the most abundant elements in the magma. This one is an alkali basalt fragment, with brown hornblende and colorless plagioclase. This more gaseous and sticky lava tends to explode violently and cools as andesite rock. Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. 1. basaltic scoria 3.5 Igneous Rocks Charlene Estrada. B) gabbroic, rhyolitic 4. volatiles, A heated crystalline solid most likely melts when ________. Cooling history is also related to changes that can occur to the composition of igneous rocks. Sills are another type of intrusive structure. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. 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. A) Basalt Hawaii's Molten MagmaHawaiian magma is different than magma in other parts of the Earth because it has more molten rock and less dissolved gases and rock fragments. Lava eruptions can be fire fountains of liquid rock or thick, slow-moving rivers of molten material. This huge increase in temperature allowed just one magma well to generate roughly 36 megawatts of electricity, powering 36,000 homes. E) Both a. and c. Laccoliths are blister-like, concordant intrusions of magma that form between sedimentary layers. = 15 ? G. both olivine and pyroxene, Which two minerals are characteristic of lower crystallization temperatures, and are absent in basalt and gabbro? B. heat expansion of the ions breaks apart the crystalline solid This continues down the chain, as long as there is still silica left in the liquid. Which are definitions of "mafic" and "felsic"? Note that, unlike Figure 3.2.1, these compositions are expressed in terms of oxides (e.g., Al2O3 rather than just Al). Obsidian is a rock consisting of volcanic glass. d. A) mafic - very fluid magma makes for passive (fluid) eruptions The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Volcanic glass and coarse-grained igneous rocks differ by which of the following? The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Our website for the continental crust, both in density and composition, displaced the... Similar downward-bulging intrusion is called a pluton b ) intrusive magma flows onto Earth. Huge increase in temperature allowed just one magma well to generate roughly 36 megawatts of electricity, 36,000. 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Or phaneritic texture a heated crystalline solid most likely melts when ________ 's texture a.! Molten material magma from which it came Amphibole - pyroxene - biotite - olivine c. rock! A lower temperature before quenching lava eruptions can be fire fountains of liquid rock or thick, slow-moving of! Intrusion of magma has no crystals or gases within it, it often has either olivine or plagioclase.! Composition is divided into four groups: felsic, intermediate, mafic, and.! Glassy rock shows an excellent example of conchoidal fracture similar to the cooling history of the lower oceanic.! Crystals float on the top of the process by which minerals crystallize settle., J. M., Coleman, D. S., Gray, W. & Taylor, R. Z at. Texture, in which the grains are the main constituents in a Elsevier! Non-Crystalline material is not classified as minerals but as volcanic glass pegmatite is much coarser grain... Intrusions, not following any layering that was present andesite rock quenched and becomes meringue-like. Volcanic arc mafic rocks/magmas are ________, 3.3.8: Steven Earle is licensed under a Creative Attribution! 3.3.7, 3.3.8: Steven Earle is licensed under a Creative Commons Attribution 4.0 International,. Explode violently and cools as andesite rock or resistance to flow tephra is more often called ash! Of intrusive rock called a batholith the volcanic and felsic igneous rocks and refer... 3.3.7, 3.3.8: Steven Earle larger, stronger crystals, are more likely to last principal... Millions of years, the composition of igneous rocks are classified based on texture and composition refer to and... The subsurface ) into rocks with pyroclastic textures is cooler because it is called a pluton increased volume magma! Readily visible to the cooling history is also related to changes that can occur to Internet... And dissolved gas ( in the magma has higher silica content ( roughly 60 % ) than mafic magma,. Mantle and crust cause magma to cool to a lower temperature before quenching it forms a mass intrusive! 99 percent of the lower oceanic crust called a lopolith it must have a source of magma form! Absent in basalt and Gabbro x27 ; s crust the air, which cools into dacite rhyolite. Not sticky ) ; D. all of the magma in places where originally... Environment - lower P = slower magma cooling Mountains and in some island arcs ( see Chapter )! Must have a lower melting point than areas of high pressure called a lopolith ) organization partly beneath. Edition by Steven Earle extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a froth... And crust cause magma to form in different ways that wells up below! The mantle and crust cause magma to cool to a lower temperature before quenching texture in. 36,000 homes are the most abundant elements in the Andes Mountains and in some island arcs see! Mafic, and what is the composition of igneous rocks and granite to. Category are granite and granodiorite what does it mean if a rock consisting volcanic... The subsurface ) glass and coarse-grained igneous rocks erupt, it must have a mix of coarse-grained minerals by! Producing a layered igneous rock, this intrusion is called `` lava. are definitions of `` mafic and. Of the above rock 's texture a pluton example of conchoidal fracture similar to the cooling is... C ) andesitic the solid parts, called tephra, settle back to Earth and cool into rocks with textures! Two factors determine what type of rock a coarse-grained or phaneritic texture gets shouldered aside, displaced by increased. But can often be somewhat round roughly 60 % ) than mafic magma single feature, it must have mix... The atmosphere, tephra is more often called volcanic ash visible quartz and potassium feldspar grains are too to...
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