1. diorite and gabbro The Journal of Geology 39, 5467 (1931). 3. decompression melting C) gabbroic If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. b. A) mafic - very fluid magma makes for passive (fluid) eruptions These rocks are rare on the surface, but make up peridotite, the rock of the upper mantle. When porphyritic, it often has either olivine or plagioclase phenocrysts. __________ is characterized by very coarse mineral grains? Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). When many plutons merge together in an extensive single feature, it is called a batholith. E) Both a. and c. Igneous rocks form when melted rock cools. As the liquid rock solidifies, it loses its heat to the surrounding crust. D) komatiite It can be found in the right below a or within the . E. intermediate silica, intermediate iron and magnesium, aphanitic texture C. potassium feldspar in Developments in Precambrian Geology (ed. This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. 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) . Regardless, when a diapir cools, it forms a mass of intrusive rock called a pluton. Why? They are typically more than 100 km2 in area, associated with subduction zones, and mostly felsic in composition. 6. basalt E. pumice, On a global basis, most of the world's magma is generated in which part of the Earth? 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). An eruption reduces the pressure inside the magma chamber. why is it helpful to measure the specific gravity of a mineral? This type of magma has a low gas content and low viscosity, or resistance to flow. B) the rock's likely parent magma composition Rhyolite is commonly pink and will often have glassy quartz phenocrysts. Which of the following can account for variations in a magma/rock composition? America. D) the minerals, Match the following rock names with the associated rock names of the same composition, but different texture. D. Biotite - amphibole - pyroxene - olivine, According to Bowen's reaction series, which of the following minerals has the highest crystallization temperature? Thick, viscous felsic magma can trap gas bubbles in a volcanos magma chamber. B) amount of space available for crystals to fill Normally, geothermal energy is created by pumping water into hot volcanic bedrock, creating steam that is then harnessed to generate electricity. If a media asset is downloadable, a download button appears in the corner of the media viewer. The black colors are likely two or three different minerals. B. variable silica, iron and magnesium content, glassy texture This continues down the chain, as long as there is still silica left in the liquid. 6 2/3 B. This one is an alkali basalt fragment, with brown hornblende and colorless plagioclase. Batholiths and stocks are discordant intrusions that cut across and through surrounding country rock. Andesite is a fine crystalline intermediate extrusive rock. Condie) 11, 1144 (Elsevier, 1994). For igneous rock, the composition is divided into four groups: felsic, intermediate, mafic, and ultramafic. The other is how fast the magma cools. C. Al and Si are the least abundant elements in the magma. 1. aphanitic Extrusive or volcanic rocks crystallize from lava at the earth's surface. The __________ of an igneous rock involves the sizes, shapes and arrangements of mineral grains. Plus, they are, by definition, exposed to the elements of erosion immediately. Stage 1 The core is the superheated center, the mantle is the thick, middle layer, and the crust is the top layer on which we live. Haydn's opus 33 string quartets were first performed for B) the rock's composition 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. Salt Lake Community College via OpenGeology. Diorite is a coarse-crystalline intermediate intrusive igneous rock. 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. 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. Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. E. phaneritic texture, relatively high silica content 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. Granite is a good approximation for the continental crust, both in density and composition. K.C. 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. biotite and olivine Dikes are therefore discordant intrusions, not following any layering that was present. Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. In a porphyritic volcanic rock, which mineral grains are the last to crystallize? C) highly fluid, cools quickly It is poor in silica, in the 40% or less range. C) The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. It has also been proposed that diapirs are not a real phenomenon, but just a series of dikes that blend into each other. A. C) Mafic is hard rock, felsic is soft rock. B) granodioritic One of the most spectacular types of pyroclastic deposit is an ignimbrite, which is the deposit of a ground-hugging pumiceous pyroclastic density current (a rapidly flowing hot suspension of pyroclasts in gas). A) andesitic A __________ texture would be most UNLIKELY to occur in an extrusive igneous rock. Diorite is identifiable by its Dalmatian-like appearance of black hornblende and biotite and white plagioclase feldspar. B) the magma stays the same temperature, causing ions to slow down and form crystals, mostly Si-O tetrahedra B. the upper mantle Composition refers to a rocks chemical and mineral make-up. The gas bubbles become trapped in the solidifying lava to create a vesicular texture, with the holes specifically called vesicles. 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. D) The rock contains broken fragments and is volcanic in origin. E. pyroxene, Which one of the following rock types is most likely to contain calcium-rich feldspar? 3. extrusive igneous rock Match the rock name with the best description. Lava cools to form volcanic rock as well as volcanic glass. Please select the best answer from the choices provided C. the introduction of volatiles (e.g., water) Dikes are therefore discordant intrusions, not following any layering that was present. Match the igneous rock texture and its appropriate description. = 2 1/4. B. may be composed of grains of olivine and pyroxene phenocrysts Learn how BCcampus supports open education and how you can access Pressbooks. C) aphanitic 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. A) The glass is formed mostly when lava cools in a volcano whereas phaneritic rocks cool at the surface. Igneous rocks are defined as types of rocks that are formed when molten rock (rock liquefied by intense heat and pressure) cools to a solid state. It is commonly vesicular and aphanitic. It erupts non-explosively and moves very quickly when it reaches Earths surface as lava. Composition refers to the rock's specific mineralogy and chemical composition. C. basalt Gabbro is a major component of the lower oceanic crust. To avoid these complications, the following figure presents a simplified version of igneous rock nomenclature focusing on the four main groups, which is adequate for an introductory student. When lava is extruded onto the surface, or intruded into shallow fissures near the surface and cools, the resulting igneous rock is called extrusive or volcanic. In comparison, one single wind turbine generates between 1 to 3 megawatts. Intrusive rocks, forming underground with larger, stronger crystals, are more likely to last. Note that these 8 elements make up about 99 percent of the Earth's crust. = 45/20 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. F, In order to scan rsums, employers will use a scanner which looks like a compact copy machine. D) granite; intrusive rock that formed from cooling of relatively intermediate silica magma Low viscosity means that mafic magma is the most fluid of magma types. If magma cools slowly, deep within the crust, the resulting rock is called intrusive or plutonic. Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. Condie) 11, 1144 (Elsevier, 1994). As it falls to Earth, tephra includes rocks such as pumice. Magmas derived from crustal material are dominated by oxygen, silicon, aluminum, sodium, and potassium. Arndt, N. T. Chapter 1 Archean Komatiites. 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. 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. A) the rock's texture Mysterious MagmaMagma is usually studied as lava or igneous rock. 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. The Henry Mountains of Utah are a famous topographic landform formed by this process. 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. As a mafic magma starts to cool, some of the silica combines with iron and magnesium to make olivine. The compositions of typical mafic, intermediate, and felsic magmas are shown in Figure 3.3.4. 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. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. 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. This answer has been confirmed as correct and helpful. What are the other two, smaller percentage components of most magmas? 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. For a volcano to erupt, it must have a source of magma. A. quartz and pyroxene B) glassy B) Temperature of the environment - lower T = slower magma cooling. D. and c. only Plutons can include dikes and xenoliths. 15-30 seconds __________ is a volcanic rock that is extremely vesicular and glassy. Classification of Igneous Rock Series. Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. C. granite An extrusion could include lava and volcanic rock. In violent eruptions, the volume of magma shrinks so much that the entire magma chamber collapses and forms a caldera. A rock that chiefly consists of pegmatitic texture is known as a pegmatite. If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture. A significant exception to this is active volcanoes, which are discussed in a later section on volcanism. Are plutons assembled over. Extrusive rocks, because of their small crystals and glass, are less durable. An active volcano always has a magma chamber beneath the cone. This texture, which indicates a very slow crystallization, is called pegmatitic. Chemical data for four rock samples are shown in the following table. A. Bowen's reaction process Batholiths are found in the cores of many mountain ranges, including the granite formations of Yosemite National Park in the Sierra Nevada of California. Stage 3, Instead of having to know HTML code, most Web sites will have templates that make creating Web rsums easy. This texture, which indicates a very slow crystallization, is called pegmatitic. 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]. True D) peridotite, Most magmas are dominantly molten rock (a liquid called "melt"). Over millions of years, many magma chambers simply cool to form a pluton or large igneous intrusion. This is a common component of volcanic ash and rocks like obsidian. 2. porphyritic andesite Pyro, meaning fire, refers to the igneous source of the tephra and clastic refers to the rock fragments. To avoid these complications, the following figure presents a simplified version of igneous rock nomenclature focusing on the four main groups, which is adequate for an introductory student. Why do all magmas create dominantly silicate minerals upon cooling? There are 3 main agents that cause metamorphism. C. assimilation The layers of magma may be documented by the type of eruption material the volcano emits. The least-dense magma rises to the top. 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. An igneous rock is any crystalline or glassy rock that forms from cooling of a magma.. 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.. Magma can cool to form an igneous rock either on the surface of the Earth . Figure 3.3.1, 3.3.4, 3.3.5, 3.3.6, 3.3.7, 3.3.8: Steven Earle. Peacock, M. A. Gabbro is a major component of the lower oceanic crust. Factors that cause an increase in Temperature, Pressure, and Chemical changes are the three agents that we are going to study. 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. Want to create or adapt OER like this? D) phaneritic, __________ is named for a prominent, volcanic mountain range in western South D) dark colored, less dense and more viscous (sticky); The rifting movement causes the buoyant magma below to rise and fill the space of lower pressure. 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. A) andesite T Composition refers to the rocks specific mineralogy and chemical composition. 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. Magma is a molten and semi- molten rock mixture found under the surface of the Earth. In order to scan resumes, employers will use a scanner which looks like a compact copy machine. B) Mafic is a magma/rock that is rich in Fe and Mg, whereas felsic refers to that which is rich in feldspar and silica (quartz) 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. B) The rock has mineral grains that are glassy. E) None of these. 2. The Hawaiian Islands are a direct result of mafic magma eruptions. Because mafic lava is more mobile, it is less common than basalt. C. the lower crust B. Olivine - pyroxene - amphibole - biotite These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. User: She worked really hard on the project. flowing rock above Earths surface, When your rsum is first reviewed, a potential employer looks at it for approximately _____. 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). Glazner, A. F., Bartley, J. M., Coleman, D. S., Gray, W. & Taylor, R. Z. 1996 - 2023 National Geographic Society. 20/3 A) Intrusive magma is cooler because it is well insulated by the surrounding rock. 1. The most important factor affecting the mineral composition of an igneous rock is ________. A. the rock has two or more distinctly different-size populations of mineral grains Rocks labeled as granite in laymen applications can be several other rocks, including syenite, tonalite, and monzonite. Because felsic lavas are less mobile, it is less common than granite. Magma that has cooled into a solid is called igneous rock. 1. C) granite d. B) considered "plutonic" rocks because they form from magma beneath the surface; considered "volcanic" because they form from lava erupted from a volcano. D. Heavier crystals float on the top of the magma in the magma chamber producing a layered igneous rock upon complete solidification. Granite is a course-crystalline felsic intrusive rock. A) rate of cooling 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. When volcanoes erupt explosively, vast amounts of lava, rock, ash, and gases are thrown into the atmosphere. Explanation: Advertisement 4. mafic obsidian. The minerals present will be olivine, pyroxene, and calcium-rich plagioclase. As cooling continues, the various reactions on the discontinuous branch will proceed because silica is abundant, the plagioclase will become increasingly sodium-rich, and eventually potassium feldspar and quartz will form. Book: An Introduction to Geology (Johnson, Affolter, Inkenbrandt, and Mosher), { "5.01:_Classification_of_Igneous_Rocks" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
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