B) glassy 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. Chapter 6 Sediments and Sedimentary Rocks, Chapter 7 Metamorphism and Metamorphic Rocks, Chapter 21 Geological History of Western Canada, Chapter 22 The Origin of Earth and the Solar System, Creative Commons Attribution 4.0 International License. Andesite is a fine crystalline intermediate extrusive rock. D) the magma cools causing ions to come closer together, the first ions being Si and O to form Si-O tetrahedra. National Geographic Headquarters 1145 17th Street NW Washington, DC 20036. 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? A single magma may generate several mineralogically different igneous rocks. 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. Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. Match the igneous rock texture and its appropriate description. B) mineral composition A sill is a concordant intrusion that runs parallel to the sedimentary layers in the country rock. A) basaltic, gabbroic Classification of Igneous Rock Series. Another is the native rock is melted and consumed into the rising magma or broken into pieces that settle into the magma, a process known as stoping. These eruptions eject lava violently into the air, which cools into dacite and rhyolite rock. If magma cools slowly, deep within the crust, the resulting rock is called intrusive or plutonic. E. intermediate silica, intermediate iron and magnesium, aphanitic texture Lava eruptions can be fire fountains of liquid rock or thick, slow-moving rivers of molten material. E. granite, According to Bowen's reaction series for cooling magma, which mineral(s) is/are likely to form a phenocryst in porphyritic basalt? The cooling behaviour of intermediate magmas lie somewhere between those of mafic and felsic magmas. These rocks usually have a coarse texture (individual minerals are visible without magnification), because the magma cools slowly underground, allowing crystal growth. False, Applications and Investigations In Earth Science, Dennis G. Tasa, Edward J. Tarbuck, Frederick K. Lutgens, Charles C. Plummer, Diane Carlson, Lisa Hammersley. 4. pillow basalt, __________ composition lava is erupted at ocean ridges, whereas ____________ composition lava is erupted on continents. But most magma remains molten or partly molten beneath Earths surface. 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. What is the most important factor for whether a magma cools slowly or quickly? 2. gabbro These compounds cause the rock to melt at lower temperatures. As a volcanos magma chamber experiences greater pressure, often due to more magma seeping into the chamber, the volcano may undergo an eruption. When it cools to solid rock, this intrusion is often called a pluton. This is a common component of volcanic ash and rocks like obsidian. Because mafic lava is more mobile, it is less common than basalt. Low viscosity means that mafic magma is the most fluid of magma types. B. Andes mountains volcanoes B. magma mixing When porphyritic, it often has either olivine or plagioclase phenocrysts. Mafic MagmaMafic magma has relatively low silica content, roughly 50%, and higher contents in iron and magnesium. Composition refers to a rocks chemical and mineral make-up. What would happen if you replaced the ">=" operator in the test with ">" so that it reads St. Helens. B) granodioritic Composition refers to the rock's specific mineralogy and chemical composition. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. LAVA - magma that reaches the Earth's surface before cooling (most gasses have escaped). C. basalt The most abundant elements are oxygen and silicon, followed by aluminum, iron, calcium, sodium, magnesium, and potassium. User: Alcohol in excess of ___ proof Weegy: Buck is losing his civilized characteristics. Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. In fact, magma has only been discovered three times in its natural habitat deep in Earths crust. C. high silica, low iron and magnesium, phaneritic texture 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) Pressure of the environment - higher P = slower magma cooling. 1. diorite and gabbro A. crystal settling B) Andesite E. pyroxene, Which one of the following rock types is most likely to contain calcium-rich feldspar? K.C. C) considered "plutonic" rocks because they form from lava extruded at the surface; considered "volcanic" rocks because they form from magma beneath the surface. Added 2/10/2022 11:11:08 PM This answer has been confirmed as correct and helpful. When many plutons merge together in an extensive single feature, it is called a batholith. [Hint] What is magma? In comparison, one single wind turbine generates between 1 to 3 megawatts. if((replacementValue > 0) && (replacementValue < limit)). A purely descriptive definition is that a rock is - A naturally occurring aggregate of minerals and other solid material. 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 identifiable by its Dalmatian-like appearance of black hornblende and biotite and white plagioclase feldspar. Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. 3.5 Igneous Rocks Charlene Estrada. In some cases, extrusive lava cools so rapidly it does not develop crystals at all. D) highly viscous, cools quickly, Crystallization of magma occurs when ________. The Journal of Geology 39, 5467 (1931). A magma chamber is a large underground reservoir of molten rock. __________ is characterized by very coarse mineral grains? A. Bowen's reaction process Diorite is a coarse-crystalline intermediate intrusive igneous rock. Laccoliths bulge upwards; a similar downward-bulging intrusion is called a lopolith. Igneous rocks contain information about how they originate. The solid parts, called tephra, settle back to earth and cool into rocks with pyroclastic textures. 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. Introduction to Igneous Rocks. This occurs when calcium-rich early-forming plagioclase crystals become coated with progressively more sodium-rich plagioclase as the magma cools. 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. Lava is molten rock flowing out of fissures or vents at volcanic centres (when cooled, they form rocks such as basalt, rhyolite, or obsidian). A. Si and O are the most abundant elements in the magma. a. Classification of Igneous Rock Series. C. cause rocks to melt at lower temperatures, magnified by an increase in pressure, important at convergent plate boundaries 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). Lava that cools extremely quickly may not form crystals at all, even microscopic ones. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Areas of lower pressure always have a lower melting point than areas of high pressure. America. Lava that cools extremely quickly may not form crystals at all, even microscopic ones. Magma Chamber In areas where temperature, pressure, and structural formation allow, magma can collect in magma chambers. Granite is a good approximation for the continental crust, both in density and composition. in Developments in Precambrian Geology (ed. 5. pumice D) dark colored, less dense and more viscous (sticky); Obsidian is a rock consisting of volcanic glass. 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. Some pumice is so full of vesicles that the density of the rock drops low enough that it will float. It is commonly vesicular and aphanitic. F, During this stage of rsum review, employers use the rsum to guide interview questions: Magma is molten rock below Earths surface. 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). Magma is like seltzer: It contains "Volatile gases" - H2O, CO2, SO2, N2, CH4and other dissolved gases. Classification of Igneous Rock Series. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. C) Lava is the name given to the ejected magma from a passive (fluid) volcano, but it is still called "magma" if it is erupted explosively, like at Mt. 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. C) The glass is formed mostly when magma is formed whereas the phaneritic rocks are formed in a volcano. C) basalt; extrusive rock that formed from cooling of relatively high silica lava Mafic rocks/magmas are ________, whereas felsic rocks/magmas are ________. A pluton is an intrusion of magma that wells up from below the surface. solid rock with a fine texture cooled rock with large crystals molten rock below Earth's surface flowing rock above Earth's surface New answers Rating 3 capslock Magma is molten rock below Earth's surface. 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. Differences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways. This relates to the cooling history of the molten magma from which it came. Diorite is a coarse-crystalline intermediate intrusive igneous rock. Arndt, N. T. Chapter 1 Archean Komatiites. 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). Regardless, when a diapir cools, it forms a mass of intrusive rock called a pluton. In the atmosphere, tephra is more often called volcanic ash. Rock formed from large deposits of tephra fragments is called tuff. The means that the overall composition of the magma near the top of the magma chamber will become more felsic, as it is losing some iron- and magnesium-rich components. Composition refers to the rocks specific mineralogy and chemical composition. B. heat expansion of the ions breaks apart the crystalline solid 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. The rock that results from this is an igneous rock from the Latin word ignis, meaning "fire." C. the introduction of volatiles (e.g., water) T __________ is a volcanic rock that is extremely vesicular and glassy. Rhyolite is commonly pink and will often have glassy quartz phenocrysts. A) The rock is crystalline, but mineral grains are of distinctly different sizes. B. olivine and pyroxene B) considered "plutonic" rocks because they form from magma beneath the surface; considered "volcanic" because they form from lava erupted from a volcano. One theory is the overriding rock gets shouldered aside, displaced by the increased volume of magma. Regardless, when a diapir cools, it forms a mass of intrusive rock called a pluton. The sequence in which minerals crystallize from a magma is known as the Bowen reaction series (Figure 3.3.1 and Figure 3.3.3). A) Each vesicle was filled by a gas bubble when the lava was still mainly liquid. They are formed when magma exploits a weakness between these layers, shouldering them apart and squeezing between them. Dikes are therefore discordant intrusions, not following any layering that was present. cooled rock with large crystals How much is a steak that is 3 pounds at $3.85 per pound. Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. 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. D) granite; intrusive rock that formed from cooling of relatively intermediate silica magma C. assimilation of "foreign" rocks by the magma A) considered "volcanic" rocks because they form from magma beneath the surface; considered "plutonic" because they form from lava erupted from a volcano. D) The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. The crystals that settle might either form an olivine-rich layer near the bottom of the magma chamber, or they might remelt because the lower part is likely to be hotter than the upper part (remember, from Chapter 1, that temperatures increase steadily with depth in Earth because of the geothermal gradient). D) Temperature of the environment - higher T = slower magma cooling. D) The rock contains broken fragments and is volcanic in origin. D. Biotite - amphibole - pyroxene - olivine, According to Bowen's reaction series, which of the following minerals has the highest crystallization temperature? Figure 4.1. Laccoliths bulge upwards; a similar downward-bulging intrusion is called a lopolith. Intermediate MagmaIntermediate magma has higher silica content (roughly 60%) than mafic magma. Why are thin sections of rocks used to study igneous rocks? K.C. A. convergent plate boundaries A. Pyroxene - amphibole - olivine - biotite Compare these with those in the table above to determine whether each of these samples is felsic, intermediate, or mafic. E. All of these. Which of the following can account for variations in a magma/rock composition? When you reach out to him or her, you will need the page title, URL, and the date you accessed the resource. Want to create or adapt OER like this? The individual crystals in phaneritic texture are readily visible to the unaided eye. When volcanoes erupt explosively, vast amounts of lava, rock, ash, and gases are thrown into the atmosphere. Dikes are therefore discordant intrusions, not following any layering that was present. Rocks labeled as granite in laymen applications can be several other rocks, including syenite, tonalite, and monzonite. B. an increase in heat (high temperature) This answer has been confirmed as correct and helpful. The dike is younger than the rocks it cuts across and, as discussed in the chapter on Geologic Time (Chapter 7), may be used to assign actual numeric ages to sedimentary sequences, which are notoriously difficult to age date. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. D. muscovite 2 minutes, Web rsums are posted to the Internet in HTML format. These rocks are rare on the surface, but make up peridotite, the rock of the upper mantle. Thin sections are thin slices of rocks that allow light to pass through them so that rocks may be examined using a microscope. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. The densest magma sinks near the bottom of the chamber. 4. glassy. B) highly fluid, cools slowly It can be found in the right below a or within the . CC BY. why is it helpful to measure the specific gravity of a mineral? The cracks, called fissures or vents, are tell-tale signs of a volcano. 1. aphanitic 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. 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. 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. 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]. They have a mineral composition that is intermediate between granite and basalt. 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) . A) the rock's texture C) highly fluid, cools quickly Rocks labeled as granite in laymen applications can be several other rocks, including syenite, tonalite, and monzonite. 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. The purpose of writing a rsum is to get a job. The gas bubbles become trapped in the solidifying lava to create a vesicular texture, with the holes specifically called vesicles. Slow cooling gives crystals enough time to grow to easily seen sizes (i.e., larger than 1 mm). What is magma? The core is the superheated center, the mantle is the thick, middle layer, and the crust is the top layer on which we live. 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. In this case, water overlying the subducting seafloor would lower the melting temperature of the mantle, generating magma that rises to the surface. This lava cools into basalt, a rock that is heavy and dark in color due to its higher iron and magnesium levels. 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. C) light colored, less dense and more viscous (sticky); The composition of magma depends on the rock it was formed from (by melting), and the conditions of that melting. National Geographic Society is a 501 (c)(3) organization. Decompression MeltingDecompression melting involves the upward movement of Earth's mostly-solid mantle. A. chemical bonds melt Normally, geothermal energy is created by pumping water into hot volcanic bedrock, creating steam that is then harnessed to generate electricity. Soon after that, all of the magma is used up and no further changes takes place. A number of processes that take place within a magma chamber can affect the types of rocks produced in the end. 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). B) granodioritic natural glasses organic material (lignite, coal, or petroleum) fossils. 15-30 seconds 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. The Henry Mountains of Utah are a famous topographic landform formed by this process. An extrusion could include lava and volcanic rock. D) phaneritic, __________ is named for a prominent, volcanic mountain range in western South We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. If magma cools slowly, deep within the crust, the resulting rock is called intrusive or plutonic. If magma cools slowly, deep within the crust, the resulting rock is called intrusive or plutonic. Intrusive or plutonic rocks crystallize from magma beneath the earth's surface. B) The glass is formed mostly when magma cools deep beneath the surface whereas phaneritic rocks cool at the surface. Salt Lake Community College via OpenGeology. The resulting rock is called volcanic glass. 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. Melted rock originates within Earth as magma . A) Intrusive magma is cooler because it is well insulated by the surrounding rock. User: 3/4 16/9 Weegy: 3/4 ? It is found in its namesake, the Andes Mountains as well as the Henry and Abajo mountains of Utah. Magma Escape Routes Magma leaves the confines of the upper mantle and crust in two major ways: as an intrusion or as an extrusion. Mafic magmas have 45% to 55% SiO2, about 25% total of FeO and MgO plus CaO, and about 5% Na2O + K2O. Which of the following describes best the difference between magma and lava? F) Both c. and d. - Usually, there are several mineralsin the aggregate, though some rocks may have only one. b. B) The rock has mineral grains that are glassy. Why? These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. C) solid + melt igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. D) considered "volcanic" rocks because they form from lava extruded at the surface; considered "plutonic" rocks because they form from magma beneath the surface. A) Pressure of the environment - lower P = slower magma cooling. 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The types of rocks that allow light to pass through them so that rocks may be examined using a.. Most abundant elements in the atmosphere rapidly it does not develop crystals at all several other rocks including. Ions to come closer together, the resulting rock is - a occurring... Good approximation for the continental crust, what is magma solid rock with a fine texture Andes mountains volcanoes b. magma mixing when porphyritic, it is a... The altered rhyolite that makes up the rocks specific mineralogy and chemical composition larger than 1 mm ) so of... The most important factor for whether a magma chamber can affect the types of rocks used to igneous! Crust cause magma to form in different ways cooled rock with large crystals How much is a steak is... Of volcanic glass discovered three times in its natural habitat deep in crust. On the surface whereas phaneritic rocks cool at the surface whereas phaneritic rocks are formed a! 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