The gas bubbles become trapped in the solidifying lava to create a vesicular texture, with the holes specifically called vesicles. Dikes are therefore discordant intrusions, not following any layering that was present. All rights reserved. A single magma may generate several mineralogically different igneous rocks. When you reach out to him or her, you will need the page title, URL, and the date you accessed the resource. T If the fragments accumulate while still hot, the heat may deform the crystals and weld the mass together, forming a welded tuff. Many xenoliths are crystals torn from inside the Earth and embedded in magma while the magma was cooling. D. consist of very coarse grained crystals of potassium feldspar, muscovite and quartz B. volume is very large, comparable in size with granitic batholiths A. Kilauea volcano, Hawaii It can be found in the Andes Mountains and in some island arcs (see. Gabbro is a major component of the lower oceanic crust. E. intermediate silica, intermediate iron and magnesium, aphanitic texture Which of the following best describes an aphanitic texture? 1. aphanitic C. biotite and olivine Diorite is a coarse-crystalline intermediate intrusive igneous rock. Norman Levi Bowen, born in Kingston Ontario, studied geology at Queens University and then at MIT in Boston. What is "magmatic differentiation"? 3. rhyolite It has also been proposed that diapirs are not a real phenomenon, but just a series of dikes that blend into each other. Andesitic rocks are often found at continental volcanic arcs, such as the Andes Mountains in South America, after which they are named. There are three different types of . - Usually, there are several mineralsin the aggregate, though some rocks may have only one. This section will focus on the common igneous bodies which are found in many places within the bedrock of Earth. Sills are another type of intrusive structure. B) gabbroic, rhyolitic In some cases, extrusive lava cools so rapidly it does not develop crystals at all. In comparison, one single wind turbine generates between 1 to 3 megawatts. Composition refers to a rocks chemical and mineral make-up. A. Pyroxene - amphibole - olivine - biotite A. high levels are necessary for melting of rocks 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. 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. 6. basalt They are typically more than 100 km2 in area, associated with subduction zones, and mostly felsic in composition. Composition refers to the rock's specific mineralogy and chemical composition. Which of the following describes best the difference between magma and lava? light colored, less dense and more viscous (sticky) Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. The minerals that make up igneous rocks crystallize at a range of different temperatures. Weegy: 15 ? A significant exception to this is active volcanoes, which are discussed in a later section on volcanism. 2. porphyritic This results in a higher gas content and viscosity. B. Si and O are the least abundant elements in the magma. As it cools further, much of the remaining silica goes into calcium-rich plagioclase, and any silica left may be used to convert some of the olivine to pyroxene. Most magma chambers sit far beneath the surface of the Earth. 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. E) None of these. Which mineral would you expect to see as a, Which of the following igneous rocks exhibit aphanitic texture? A) The glass is formed mostly when lava cools in a volcano whereas phaneritic rocks cool at the surface. Much like heat transfer, flux melting also occurs around subduction zones. 20/3 A. crystal settling A) pyroclastic If you have questions about licensing content on this page, please contact ngimagecollection@natgeo.com for more information and to obtain a license. C) gabbroic Want to create or adapt OER like this? 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. 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]. How Magma Forms Earth is divided into three general layers. 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). D. occurs when confining pressure drops significantly, like under the ocean ridges 2. porphyritic andesite Lava flows are typically finer grained than intrusive igneous rocks. 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). This relates to the cooling history of the molten magma from which it came. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. 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). 3. Dikes are therefore discordant intrusions, not following any layering that was present. 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) . 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? Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. 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. 4. porphyritic basalt Texture describes the physical characteristics of the minerals, such as grain size. B. komatiite This magma solidifies in the air to form volcanic rock called tephra. Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. It can be found in the Andes Mountains and in some island arcs (see. True They have a mineral composition that is intermediate between granite and basalt. The dikes may be intruding over millions of years, but since they may be made of similar material, they would be appearing to be formed at the same time. C) Pegmatite Granite: Granite is the intrusive equivalent of rhyolite but has a coarser texture. The dikes may be intruding over millions of years, but since they may be made of similar material, they would be appearing to be formed at the same time. Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. 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 large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. 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. C. Crystal settling may produce different melting conditions for a rock in different plate tectonic scenarios. LAVA - magma that reaches the Earth's surface before cooling (most gasses have escaped). Examples of rhyolite include several lava flows in Yellowstone National Park and the altered rhyolite that makes up the Grand Canyon of the Yellowstone. F) basalt; extrusive rock that formed from cooling of relatively low silica lava, Match the volcano with the appropriate rock formed by its eruption. Igneous rocks are classified based on texture and composition. _________ is the dominant feldspar in basalt. Compare these with those in the table above to determine whether each of these samples is felsic, intermediate, or mafic. 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]. In this case, water overlying the subducting seafloor would lower the melting temperature of the mantle, generating magma that rises to the surface. 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. If no button appears, you cannot download or save the media. dark colored, more dense and less viscous (not sticky) Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. MAGMA - molten material and dissolved gas (in the subsurface). A) granite Please select the best answer from the choices provided She or he will best know the preferred format. Felsic magmas tend to be cooler than mafic magmas when crystallization begins (because they dont have to be as hot to remain liquid), and so they may start out crystallizing pyroxene (not olivine) and plagioclase. B. may be composed of grains of olivine and pyroxene phenocrysts St. Helens. D) dark colored, less dense and more viscous (sticky); It is found in its namesake, the Andes Mountains as well as the Henry and Abajo mountains of Utah. Decompression melting often occurs at divergent boundaries, where tectonic plates separate. They have textures or mineralogy different than the surrounding material, and so are generally easy to spot. Thus, you can often figure out the relative order in which the minerals crystallized from the magma. 4. volatiles, A heated crystalline solid most likely melts when ________. A) andesitic A) the magma heats up and ions in crystals break their bonds due to expansion and Si and O ion vibration The pool of magma in a magma chamber is layered. In 1912, Norman Levi Bowenhe joined the Carnegie Institution in Washington, D.C., where he carried out groundbreaking experimental research into the processes of cooling magmas. 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. B) the rock's likely parent magma composition Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. The word reaction is critical. Laccoliths are blister-like, concordant intrusions of magma that form between sedimentary layers. Pyroclastic texture is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments. 16/9 = Weegy: Whenever an individual stops drinking, the BAL will decrease slowly. A. chemical bonds melt D. Biotite - amphibole - pyroxene - olivine, According to Bowen's reaction series, which of the following minerals has the highest crystallization temperature? Andesite is a fine crystalline intermediate extrusive rock. B) granite; intrusive rock that formed from cooling of relatively high silica magma National Geographic News: New Magma Layer Found Deep in Earth's Mantle? The Hawaiian Islands are a direct result of mafic magma eruptions. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. These tiny crystals can be viewed under a petrographic microscope [1]. 1. diorite and gabbro 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). It is the source of all igneous rock. Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. Peacock, M. A. D) the lava in the crystallizing magma chamber before eruption. Typical felsic rocks are granite and rhyolite (Figure 3.3.5). The process by which the same magma may produce different composition igneous rocks. 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. F. dominant rock formed by the eruption of volcanic mountain ranges such as the Andes in western S. America 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. C) Both of these. 1 minute 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). These volcanic mounds can grow into volcanic islands over millions of years of activity. D) solid + crystal. 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. in Developments in Precambrian Geology (ed. B. Lava that cools extremely quickly may not form crystals at all, even microscopic ones. 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. -is what's meant by the phrase "The domesticated generations fell Weegy: A suffix is added to the end of a word to alter its meaning. Who was Bowen, and what is a reaction series? E) basalt, Which of the following rocks is likely to have the most quartz within it and why? These compounds cause the rock to melt at lower temperatures. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. Earth Science, Geology, Geography, Physical Geography. Magma forms under Earth's surface at about 800 to 1300C in the crust or mantle and erupts on Earth's surface as lava.When magma or lava cools, it solidifies by crystallization in which minerals grow within the magma or lava. National Geographic Headquarters 1145 17th Street NW Washington, DC 20036. An igneous rock is any crystalline or glassy rock that forms from cooling of a magma. An igneous rock with large crystals embedded in a matrix of much finer crystals is indicative of a two-stage cooling process, and the texture is porphyritic (Figure 3.3.7). This answer has been confirmed as correct and helpful. The rate of cooling determines the rock's texture, or size of the mineral's crystals. Parts of a volcano. This occurs when calcium-rich early-forming plagioclase crystals become coated with progressively more sodium-rich plagioclase as the magma cools. Plus, they are, by definition, exposed to the elements of erosion immediately. 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. E. All of these. Which of the following is the likely cause of a vesicular texture (open cavities in a rock)? D. a magnifying glass or microscope is needed to see individual mineral grains An intrusion can form features such as dikes and xenoliths. A sill is a concordant intrusion that runs parallel to the sedimentary layers in the country rock. 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. This hot material rises to an area of lower pressure through the process of convection. 1. B. the upper mantle Granite is a course-crystalline felsic intrusive rock. A. the rock has two or more distinctly different-size populations of mineral grains The __________ of an igneous rock involves the mineral content, and/or refers to the magma from which it solidified. D. all of the above. Examples of rhyolite include several lava flows in Yellowstone National Park and the altered rhyolite that makes up the Grand Canyon of the Yellowstone. B. Olivine - pyroxene - amphibole - biotite Plutons can have irregular shapes, but can often be somewhat round. Introduction to Igneous Rocks. = 15 ? Magma can also extrude into Earths atmosphere as part of a violent volcanic explosion. C) aphanitic Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. There are three main types of rocks: sedimentary, igneous, and metamorphic. C. biotite 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? 6. andesite, Match the rock type with the appropriate description. 1996 - 2023 National Geographic Society. This explains why a cooling magma can have some crystals within it and yet remain predominantly liquid. National Geographic Society is a 501 (c)(3) organization. Chemical data for four rock samples are shown in the following table. B) the rock's composition 4. mafic obsidian. In violent eruptions, the volume of magma shrinks so much that the entire magma chamber collapses and forms a caldera. C) andesitic In the discontinuous branch, olivine is typically the first mineral to form (at just below 1300C). The least-dense magma rises to the top. Rhyolite is commonly pink and will often have glassy quartz phenocrysts. Are plutons assembled over. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. A. Si and O are the most abundant elements in the magma. Log in for more information. D) Temperature of the environment - higher T = slower magma cooling. As a mafic magma starts to cool, some of the silica combines with iron and magnesium to make olivine. Plutons can include dikes and xenoliths. 2. A sill is a concordant intrusion that runs parallel to the sedimentary layers in the country rock. TRUE. D) pressure. The Henry Mountains of Utah are a famous topographic landform formed by this process. 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. This is a common component of volcanic ash and rocks like obsidian. 7. obsidian, Which of the following is characteristic of pegmatites? 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. phaneritic texture, relatively low silica content The cracks, called fissures or vents, are tell-tale signs of a volcano. 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. Gabbro is a major component of the lower oceanic crust. F, In order to scan rsums, employers will use a scanner which looks like a compact copy machine. Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. In the atmosphere, tephra is more often called volcanic ash. Intrusive rocks, forming underground with larger, stronger crystals, are more likely to last. 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. The slow cooling process allows crystals to grow large, giving the intrusive igneous rock a coarse-grained or phaneritic texture. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. B. B) the magma stays the same temperature, causing ions to slow down and form crystals, mostly Si-O tetrahedra As the temperature continues to drop, olivine becomes unstable while pyroxene becomes stable. A magmatic dike is simply a large slab of magmatic material that has intruded into another rock body. For example, it is not known what happens to the pre-existing country rock as the diapir intrudes. 2. rhyolite Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). D) The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. . What does it mean if a rock has a coarse texture? An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________. 1. D) Each vesicle is filled by air and water. Andesite is a fine crystalline intermediate extrusive rock. 2.1 Electrons, Protons, Neutrons, and Atoms, 4.5 Monitoring Volcanoes and Predicting Eruptions, 5.3 The Products of Weathering and Erosion, 6.3 Depositional Environments and Sedimentary Basins, 7.5 Contact Metamorphism and Hydrothermal Processes, 9.1 Understanding Earth Through Seismology, 10.1 Alfred Wegener: The Father of Plate Tectonics, 10.2 Global Geological Models of the Early 20th Century, 10.3 Geological Renaissance of the Mid-20th Century, 10.4 Plate, Plate Motions, and Plate Boundary Processes, 11.5 Forecasting Earthquakes and Minimizing Damage and Casualties, 15.1 Factors That Control Slope Stability, 15.3 Preventing, Delaying, Monitoring, and Mitigating Mass Wasting, 21.2 Western Canada during the Precambrian, 22.2 Forming Planets from the Remnants of Exploding Stars, Appendix 1: List of Geologically Important Elements and the Periodic Table. 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This, dikes are therefore discordant intrusions, not following any layering that was present the upper mantle granite a. Occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like of... This occurs when calcium-rich early-forming plagioclase crystals become coated with progressively more sodium-rich as! Elements of erosion immediately often Figure out the relative order in which minerals crystallize a! In magma while the magma of scoria occurs when calcium-rich early-forming plagioclase crystals become coated with progressively sodium-rich...