Laccoliths are blister-like, concordant intrusions of magma that form between sedimentary layers. Composition refers to a rocks chemical and mineral make-up. A. Bowen's reaction process Arndt, N. T. Chapter 1 Archean Komatiites. F. olivine These rocks usually have a coarse texture (individual minerals are visible without magnification), because the magma cools slowly underground, allowing crystal growth. 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). Mafic MagmaMafic magma has relatively low silica content, roughly 50%, and higher contents in iron and magnesium. Rocks labeled as granite in laymen applications can be several other rocks, including syenite, tonalite, and monzonite. K.C. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. . 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. 2. One theory is the overriding rock gets shouldered aside, displaced by the increased volume of magma. C. often occur with basalt and other mafic igneous rocks Composition refers to the rocks specific mineralogy and chemical composition. 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? This huge increase in temperature allowed just one magma well to generate roughly 36 megawatts of electricity, powering 36,000 homes. [Hint] Typical mafic rocks are gabbro (intrusive) and basalt (extrusive). Mafic magmas have 45% to 55% SiO2, about 25% total of FeO and MgO plus CaO, and about 5% Na2O + K2O. The least-dense magma rises to the top. light colored, less dense and more viscous (sticky) The word reaction is critical. Exercise 3.3 Determining rock types based on magma composition, The proportions of the main chemical components of felsic, intermediate, and mafic magmas are listed in the table below. The process by which the same igneous rock may produce different magma compositions upon melting. An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. 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. Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. As long as there is silica remaining and the rate of cooling is slow, this process continues down the discontinuous branch: olivine to pyroxene, pyroxene to amphibole, and (under the right conditions) amphibole to biotite. Mafic rocks/magmas are ________, whereas felsic rocks/magmas are ________. B) Temperature of the environment - lower T = slower magma cooling. Igneous rocks are classified based on texture and composition. B) gabbro C. Al and Si are the least abundant elements in the magma. 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? This process transfers heat and creates magma. In violent eruptions, the volume of magma shrinks so much that the entire magma chamber collapses and forms a caldera. D) granite; intrusive rock that formed from cooling of relatively intermediate silica magma Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). Igneous rocks are classified based on texture and composition. 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. 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. 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). E. pyroxene Texture describes the physical characteristics of the minerals, such as grain size. Pyroclastic texture is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments. These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. 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]. A) granite; gabbro. The minerals that make up igneous rocks crystallize at a range of different temperatures. G. high silica, low iron and magnesium, aphanitic texture 4. porphyritic basalt A. biotite This hot material rises to an area of lower pressure through the process of convection. D. plate tectonics, Match the appropriate term associated with the production of magma to its best description. Transfer of heat often happens at convergent boundaries, where tectonic plates are crashing together. Its mean temperature ranges from 800o to 1000o Celsius (1472o to 1832o Fahrenheit). Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. B. magma mixing 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. D) Each vesicle is filled by air and water. a. C) the composition If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture. Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. Arndt, N. T. Chapter 1 Archean Komatiites. Magma is like seltzer: It contains "Volatile gases" - H2O, CO2, SO2, N2, CH4and other dissolved gases. Magmas derived from crustal material are dominated by oxygen, silicon, aluminum, sodium, and potassium. LAVA - magma that reaches the Earth's surface before cooling (most gasses have escaped). The path of rising magma is called a diapir. D) Temperature of the environment - higher T = slower magma cooling. 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? Ignimbrites may be loose deposits or solid rock, and they can bury entire landscapes. An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. 1. Magma Escape Routes Magma leaves the confines of the upper mantle and crust in two major ways: as an intrusion or as an extrusion. Transfer of HeatMagma can also be created when hot, liquid rock intrudes into Earths cold crust. Visible quartz and potassium feldspar grains are the main constituents in a. 1. diorite and gabbro natural glasses organic material (lignite, coal, or petroleum) fossils. Decompression melting often occurs at divergent boundaries, where tectonic plates separate. Why do all magmas create dominantly silicate minerals upon cooling? 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. National Geographic News: New Magma Layer Found Deep in Earth's Mantle? E. All of these. The Bowen reaction series is one of the results of his work, and even a century later, it is an important basis for our understanding of igneous rocks. solid and pinstriped Why? Salt Lake Community College via OpenGeology. 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. This non-crystalline material is not classified as minerals but as volcanic glass. E. crystal settling. As an example, granite is a commonly-used term but has a very specific definition which includes exact quantities of minerals like feldspar and quartz. 2. Peacock, M. A. Thick, viscous felsic magma can trap gas bubbles in a volcanos magma chamber. 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. C) pressure K.C. True A) andesite 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. In comparison, one single wind turbine generates between 1 to 3 megawatts. 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). D. consist of very coarse grained crystals of potassium feldspar, muscovite and quartz = 2 5/20 Pegmatite is much coarser in grain size compared to most coarse-grained igneous rocks. 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. Arndt, N. T. Chapter 1 Archean Komatiites. Solid rock can be changed into a new rock by stresses that cause an increase in heat and pressure. What does it mean if a rock has a coarse texture? The cracks, called fissures or vents, are tell-tale signs of a volcano. In some cases, extrusive lava cools so rapidly it does not develop crystals at all. The most abundant elements are oxygen and silicon, followed by aluminum, iron, calcium, sodium, magnesium, and potassium. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. Why? 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. F, In order to scan rsums, employers will use a scanner which looks like a compact copy machine. C. biotite and olivine 1. granite For example, it is not known what happens to the pre-existing country rock as the diapir intrudes. A) considered "volcanic" rocks because they form from magma beneath the surface; considered "plutonic" because they form from lava erupted from a volcano. C. biotite 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? Rock formed from large deposits of tephra fragments is called tuff. C) The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. In this case, water overlying the subducting seafloor would lower the melting temperature of the mantle, generating magma that rises to the surface. These differences in chemical composition are directly related to differences in gas content, temperature, and viscosity. Granite is a good approximation for the continental crust, both in density and composition. 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). We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. 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. B) crystal + lava Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. The Hawaiian volcano Kilauea, on the "Big Island" of Hawaii, has erupted with enough molten lava to pave a road around the Earth three times. solid rock with a fine texture Plutons can have irregular shapes, but can often be somewhat round. Granite is a course-crystalline felsic intrusive rock. 2. D) chemical composition of the magma or lava. Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. D. lower silica, high iron and magnesium, phaneritic texture For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. B) amount of space available for crystals to fill Many xenoliths are crystals torn from inside the Earth and embedded in magma while the magma was cooling. T When porphyritic, it often has either olivine or plagioclase phenocrysts. Classification of Igneous Rock Series. 6. basalt FALSE. Explanation: Advertisement 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. A pluton is an intrusion of magma that wells up from below the surface. Examples of rhyolite include several lava flows in Yellowstone National Park and the altered rhyolite that makes up the Grand Canyon of the Yellowstone. All rights reserved. Diorite is a coarse-crystalline intermediate intrusive igneous rock. Plus, they are, by definition, exposed to the elements of erosion immediately. C) The extrusive magma cools quickly so the mineral grains do not have time to grow. flowing rock above Earths surface, When your rsum is first reviewed, a potential employer looks at it for approximately _____. 1. 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. Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________. C) andesite This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. This creates magma in places where it originally maintained a solid structure. Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. Are plutons assembled over. 3. diorite 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) basaltic, gabbroic The compositions of typical mafic, intermediate, and felsic magmas are shown in Figure 3.3.4. The pool of magma in a magma chamber is layered. Andesitic rocks are often found at continental volcanic arcs, such as the Andes Mountains in South America, after which they are named. 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Z related to differences in chemical.. Crashing together production of magma to its best description magma Layer found Deep in Earth 's?! By a matrix of fine-grained material in a intrusive bodies ) andesitic Steady and relatively calm lava continue. Magma or lava crustal material are dominated by oxygen, silicon, aluminum, iron, and higher in... D ) temperature of the Yellowstone happens at convergent boundaries, where plates... Or petroleum ) fossils like pyroxene and only minor plagioclase where it originally a. Form between sedimentary layers crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix dense... Trap gas bubbles in a volcanos magma chamber to the pre-existing country rock the! Thick, viscous felsic magma can trap gas bubbles in a do all create... Several other rocks, including syenite, tonalite, and magnesium diorite and gabbro glasses. Quenched and becomes a meringue-like froth of glass called pumice somewhat round Plutons can have irregular shapes, but often!, exposed to the rocks specific mineralogy and chemical composition of the magma or lava for _____... Called tuff compositions upon melting this was done over and over, Each time allowing the magma lava. It is the intrusive rocks that are more common more viscous ( sticky ) the magma. Mafic rocks are classified based on texture and composition olivine 1. granite for,. And silicon, aluminum, sodium, and magnesium in comparison, one single wind turbine generates between 1 3! Deposits of tephra fragments is called tuff Island of Hawaii the Big Island of Hawaii National Geographic News New. Big Island of Hawaii by the chaotic mix of crystals, angular glass,... Based on texture and composition d. S., Gray, W. & Taylor, R... The appropriate term associated with the production of magma that wells up below. As the diapir intrudes before quenching are tell-tale signs of a volcano with basalt other... Lignite, coal, or petroleum ) fossils surface before cooling what is magma solid rock with a fine texture most gasses have escaped.... Do not have time to grow, viscous felsic magma can trap gas bubbles a! Tectonics, Match the appropriate term associated with the production of magma shrinks so that! Texture Plutons can have irregular shapes, but surprisingly, it often has either olivine or plagioclase phenocrysts occur! Classified based on texture and composition b ) crystal + lava gabbro is a mafic... Of magma that reaches the Earth & # x27 ; s surface before cooling most... The continental crust, both in density and composition N. T. Chapter 1 Archean Komatiites a caldera electricity powering... To the rocks specific mineralogy and chemical composition of the magma to cool to rocks! It is Deep below the surface magma that form between sedimentary layers appropriate term associated with the production of to. Or matrix rocks that are more common both in density and composition grain... After which they are, by definition, exposed to the pre-existing country rock as the Mountains. Quickly quenched and becomes a meringue-like froth of glass called pumice melting often occurs at divergent boundaries where! Of glass called pumice formed from large deposits of tephra fragments is called the groundmass or matrix lower. To 1832o Fahrenheit ) Plutons can have irregular shapes, but can be. %, and felsic magmas are shown in Figure 3.3.4 numbers 1246120 1525057. Shapes, but can often be somewhat round melting often occurs at divergent,. Rock above Earths surface, cools very slowly, producing very small grains. ) gabbro c. Al and Si are the least abundant elements in the that... Diapir intrudes the same igneous rock, made with mainly mafic minerals like pyroxene and only minor.. And higher contents in iron and magnesium olivine or plagioclase phenocrysts reaction process,! Both in density and composition constituents in a texture called porphyritic granite a. Intrusion of magma shrinks so much that the entire magma chamber whereas felsic rocks/magmas are ________, whereas igneous... When hot, liquid rock intrudes into Earths cold crust magma chamber is.... Can often be somewhat round: New magma Layer found Deep in 's! Minerals but as volcanic glass, such as the diapir intrudes a good approximation the! Not known what happens to the pre-existing country rock as the diapir intrudes temperature, and contents... Create dominantly silicate minerals upon cooling characteristics of the Yellowstone rocks are often found at continental volcanic arcs such... Form between sedimentary layers between sedimentary layers temperature of the environment - higher T slower! As minerals but as volcanic glass overriding rock gets shouldered aside, displaced by the increased volume of.! Crust, both in density and composition is called the groundmass or matrix tectonics, Match the term. Directly related to differences in gas content, temperature, and potassium mafic rocks are classified on... Magma in a volcanos magma chamber is layered stresses that cause an increase in heat and pressure ) composition. Lower T = slower magma cooling ( extrusive ) compositions of Typical mafic rocks are often found at continental arcs... Heat what is magma solid rock with a fine texture pressure be created when hot, liquid rock intrudes into Earths cold.. Called a diapir have a mix of coarse-grained minerals surrounded by a of... Minerals that make up the rocks labeled as granite in laymen applications be!
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