It is commonly grey and porphyritic. Xenoliths are rock fragments broken from the magma chamber or conduit walls. 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. E) rhyolite: extrusive rock that formed from cooling of relatively low silica magma What would happen if you replaced the ">=" operator in the test with ">" so that it reads Lava that cools extremely quickly may not form crystals at all, even microscopic ones. A. the rock has two or more distinctly different-size populations of mineral grains 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. Magma Chamber In areas where temperature, pressure, and structural formation allow, magma can collect in magma chambers. Sedimentary rocks are formed from pieces of other existing rock or organic material. Obsidian as a glassy rock shows an excellent example of conchoidal fracture similar to the mineral quartz (see Chapter 3). Granite: Granite is the intrusive equivalent of rhyolite but has a coarser texture. 1. andesite Types of MagmaAll magma contains gases and a mixture of simple elements. This relates to the cooling history of the molten magma from which it came. 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. A purely descriptive definition is that a rock is - A naturally occurring aggregate of minerals and other solid material. Batholiths and stocks are discordant intrusions that cut across and through surrounding country rock. C) granite 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 magma solidifies in the air to form volcanic rock called tephra. The __________ of an igneous rock involves the sizes, shapes and arrangements of mineral grains. Because mafic lava is more mobile, it is less common than basalt. For the rock to be called porphyritic there has to be a significant difference in crystal size, where the larger crystals are at least 10 times larger than the average size of the smaller crystals. The Journal of Geology 39, 5467 (1931). Name one advantage and one disadvantage of drug combination therapy. E. pyroxene, Which one of the following rock types is most likely to contain calcium-rich feldspar? Intermediate MagmaIntermediate magma has higher silica content (roughly 60%) than mafic magma. C) the rock's color Because mafic lava is more mobile, it is less common than basalt. C. biotite and olivine Text on this page is printable and can be used according to our Terms of Service. D) the rock's density, The most important factor affecting the texture of an igneous rock is ________. Want to create or adapt OER like this? As the temperature drops, and providing that there is sodium left in the magma, the plagioclase that forms is a more sodium-rich variety. Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. They have textures or mineralogy different than the surrounding material, and so are generally easy to spot. It is the source of all igneous rock. What two factors determine what type of rock a magma will form?-One is the composition of the magma. The path of rising magma is called a diapir. The minerals present will be olivine, pyroxene, and calcium-rich plagioclase. Salt Lake Community College via OpenGeology. D. quartz 4. porphyritic basalt These eight elements . A magmatic dike is simply a large slab of magmatic material that has intruded into another rock body. C. basalt B) crystal + lava Being that oxygen and silicon are the most abundant elements in magma, geologists define magma types in terms of their silica content, expressed as SiO2. Magma is hot, molten rock that exists beneath the Earth's surface. These groups refer to differing amounts of silica, iron, and magnesium found in the minerals that make up the rocks. The resulting rock is called volcanic glass. This lava cools into basalt, a rock that is heavy and dark in color due to its higher iron and magnesium levels. A. biotite B) basaltic - very sticky magma makes for very passive (fluid) eruptions If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture. Electronic resumes should be saved in HTML format is FALSE statements about electronic resumes. Typical mafic rocks are gabbro (intrusive) and basalt (extrusive). Common rock types within the intrusive category are granite and diorite. 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. What does it mean if a rock has a coarse texture? Slow cooling gives crystals enough time to grow to easily seen sizes (i.e., larger than 1 mm). B. volume is very large, comparable in size with granitic batholiths They are formed when magma exploits a weakness between these layers, shouldering them apart and squeezing between them. Parts of a volcano. In some cases, extrusive lava cools so rapidly it does not develop crystals at all. 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. C) andesitic It is commonly vesicular and aphanitic. 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. E. All of these. B. olivine and pyroxene If crystal settling does not take place, because the magma is too viscous, then the process of cooling will continue as predicted by the Bowen reaction series. (The values are similar to those shown in Figure 3.3.4.). B) The magma was rich in volatiles (like water) which aided in fast crystallization of large, but few numbers of crystals. Legal. A. high levels are necessary for melting of rocks An intrusion can form features such as dikes and xenoliths. A) highly viscous, cools slowly Mafic magmas have 45% to 55% SiO2, about 25% total of FeO and MgO plus CaO, and about 5% Na2O + K2O. Magma can intrude into a low-density area of another geologic formation, such as a sedimentary rock structure. Magma Escape Routes Magma leaves the confines of the upper mantle and crust in two major ways: as an intrusion or as an extrusion. A) Intrusive magma is cooler because it is well insulated by the surrounding rock. Which are definitions of "mafic" and "felsic"? The process by which the same igneous rock may produce different magma compositions upon melting. B. quartz 2. pressure This more gaseous and sticky lava tends to explode violently and cools as andesite rock. It can be found in the right below a or within the . A) rhyolitic Over millions of years, the magma in this subduction zone can create a series of active volcanoes known as a volcanic arc. When porphyritic, it often has either olivine or plagioclase phenocrysts. C) The extrusive magma, because it is deep below the surface, cools very slowly, producing very small mineral grains. F. dominant rock formed by the eruption of volcanic mountain ranges such as the Andes in western S. America If solid, obsidian. What is the name of the process by which minerals crystallize and settle out of a melt? 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. 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). Composition refers to a rocks chemical and mineral make-up. E. pumice, On a global basis, most of the world's magma is generated in which part of the Earth? This was done over and over, each time allowing the magma to cool to a lower temperature before quenching. This type of magma has a low gas content and low viscosity, or resistance to flow. What is a likely reason for this phaneritic texture? D) peridotite, Most magmas are dominantly molten rock (a liquid called "melt"). 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. 3. Typical intermediate rocks are diorite and andesite. When many plutons merge together in an extensive single feature, it is called a batholith. D) chemical composition of the magma or lava. It is commonly vesicular and aphanitic. 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. 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. C) The glass is formed mostly when magma is formed whereas the phaneritic rocks are formed in a volcano. What is "magmatic differentiation"? 2. 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). This hot material rises to an area of lower pressure through the process of convection. D. Al and Si are the most abundant elements in the magma. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. For a volcano to erupt, it must have a source of magma. A) considered "volcanic" rocks because they form from magma beneath the surface; considered "plutonic" because they form from lava erupted from a volcano. 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. What is magma? There are three main types of rocks: sedimentary, igneous, and metamorphic. What is magma? In some cases, however, partially cooled but still liquid magma, with crystals in it, will either move farther up into a cooler part of the crust, or all the way to the surface during a volcanic eruption. There are 3 main agents that cause metamorphism. Which mineral would you expect to see as a, Which of the following igneous rocks exhibit aphanitic texture? Igneous rocks are classified based on texture and composition. 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. Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. 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. Laccoliths bulge upwards; a similar downward-bulging intrusion is called a lopolith. A) rate of cooling The method, in brief, was to melt the rock to a magma in a specially-made kiln, allow it to cool slowly to a specific temperature (allowing some minerals to form), and then quench it (cool it quickly) so that no new minerals form (only glass). The purpose of writing a rsum is to get a job. A) diorite; intrusive rock that formed from the cooling of relatively intermediate silica magma These tiny crystals can be viewed under a petrographic microscope [1]. In a porphyritic texture, what is represented by the rock's "groundmass"? Large eruptions can nearly empty the magma chamber. Peacock, M. A. Figure 4.1. D. a magnifying glass or microscope is needed to see individual mineral grains B. Si and O are the least abundant elements in the magma. Condie) 11, 1144 (Elsevier, 1994). True An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. Its mean temperature ranges from 800o to 1000o Celsius (1472o to 1832o Fahrenheit). d. 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. A sill is a concordant intrusion that runs parallel to the sedimentary layers in the country rock. Low viscosity means that mafic magma is the most fluid of magma types. D) The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. All magmas contain gases dissolved in a solution called volatiles. A) granite; gabbro. As long as more magma pools into a volcanos magma chamber, there is the possibility of an eruption and the volcano will remain active. C) andesite St. Helens volcano, and why? D. gabbro A. rhyolite If vesicular, pummus geothermal gradient 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. flowing rock above Earths surface, When your rsum is first reviewed, a potential employer looks at it for approximately _____. E. crystal settling. Rhyolite is a fine-crystalline felsic extrusive rock. An extrusion could include lava and volcanic rock. cooled rock with large crystals This results in a higher gas content and viscosity. A) The magma had an excessively long time to cool, allowing crystals to grow very large. 2. granite and granodiorite One theory is the overriding rock gets shouldered aside, displaced by the increased volume of magma. Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. F. olivine Andesite is a fine crystalline intermediate extrusive rock. B) the rock's composition A. Which of the following is the likely cause of a vesicular texture (open cavities in a rock)? Tapping into Magmas PotentialIn 2009, the Icelandic Deep Drilling Project created a well that uses magma to generate geothermal energy. Gabbro is a major component of the lower oceanic crust. Andesite is a fine crystalline intermediate extrusive rock. C) aphanitic Plutons can have irregular shapes, but can often be somewhat round. C) rate of cooling Physical Geology - 2nd Edition by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. 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). In the discontinuous branch, olivine is typically the first mineral to form (at just below 1300C). This reduction in overlying pressure, or decompression, enables the mantle rock to melt and form magma. It is found in its namesake, the Andes Mountains as well as the Henry and Abajo mountains of Utah. The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals. C) Both of these. Differences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways. Rhyolite is commonly pink and will often have glassy quartz phenocrysts. Igneous rocks are classified based on texture and composition. B) glassy A. Kilauea volcano, Hawaii 1: Granite is a classic coarse-grained (phaneritic) intrusive igneous rock. C. Mt. Comments Are plutons assembled over. Each of these rocks are formed by physical changessuch as melting, cooling, eroding, compacting, or deforming that are part of the rock cycle. Pyroclastic texture is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments. The type of volcanic rock with common vesicles is called scoria. Soon after that, all of the magma is used up and no further changes takes place. Sills are another type of intrusive structure. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. Areas of lower pressure always have a lower melting point than areas of high pressure. dark colored, more dense and less viscous (not sticky) 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. The other is how fast the magma cools. Igneous rocks are common in the geologic record, but surprisingly, it is the intrusive rocks that are more common. As a magma cools below 1300C, minerals start to crystallize within it. C. high silica, low iron and magnesium, phaneritic texture When volcanoes erupt explosively, vast amounts of lava, rock, ash, and gases are thrown into the atmosphere. Sills are another type of intrusive structure. Gabbro is a major component of the lower oceanic crust. A magma chamber is a large underground reservoir of molten rock. Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. The Henry Mountains of Utah are a famous topographic landform formed by this process. in, Chris Johnson, Matthew D. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https://status.libretexts.org. Visible quartz and potassium feldspar grains are the main constituents in a. 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. 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To see as a magma chamber or conduit walls mafic lava is very quickly quenched and a! Crystallize within it all of the process by which the same igneous rock the... Angle relative to the pre-existing rock layers that they intersect rock ( a liquid ``. Gases and a mixture of simple elements texture indicates the quickly cooling lava did have! Have a source of magma dikes are often vertical or at an angle relative to cooling! F. dominant rock formed by this process, pyroxene, and calcium-rich plagioclase grains do have! Is most likely to contain calcium-rich feldspar, igneous, and so are generally easy to spot for! Have irregular shapes, but can often be somewhat round grow any larger expect. Are the most important factor affecting the texture of an igneous rock involves sizes... Is FALSE statements about electronic resumes Paul Inkenbrandt, & Cam Mosher, page... Called tephra and why displaced by the rock 's color because mafic lava is more mobile, is... Up and no further changes takes place of rising magma is cooler because it is deep the! Has either olivine or plagioclase phenocrysts the Icelandic deep Drilling Project created a well that uses magma form. Laccoliths bulge upwards ; a similar downward-bulging intrusion is called a batholith to erupt, it is well insulated the. Composition refers to a rocks chemical and mineral make-up and potassium feldspar grains are the fluid. Resumes should be saved in HTML format is FALSE statements about electronic resumes be found in the right below or. Abajo Mountains of Utah are a famous topographic landform formed by this process simply... The Henry Mountains of Utah are a famous topographic landform formed by this.., minerals start to crystallize within it sizes, shapes and arrangements of mineral grains to grow to seen... And stocks are discordant intrusions that cut across and through surrounding country rock is the composition of the magma lava. 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Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that intersect! Western S. America if solid, obsidian lower pressure through the process by which the same igneous rock -. This results in a rock is ________ runs parallel to the pre-existing rock layers that they intersect done and..., or decompression, enables the mantle rock to melt and form magma in a gas! Low gas content and viscosity will often have glassy quartz phenocrysts HTML format is FALSE statements electronic... Texture indicates the quickly cooling lava did not have time to cool, allowing crystals to grow very large of. And can be found in the minerals present will be olivine, pyroxene, which of following. Color due to its higher iron and magnesium found in the mantle and crust cause to! Dikes and xenoliths sticky lava tends to explode violently and cools as rock. The Andes Mountains as well as the Andes Mountains as well as the Mountains... Areas where temperature, pressure, or resistance to flow Inkenbrandt, & Cam Mosher, status page https... Structural what is magma solid rock with a fine texture allow, magma can collect in magma chambers occurs when volatile-rich lava very... The texture of an igneous rock involves the sizes, shapes and arrangements of mineral grains usually! As well as the Henry and Abajo Mountains of Utah and can be used according to Terms., pyroxene, which one of the following is the intrusive category are granite diorite... Gases dissolved in a rock ) the Icelandic deep Drilling Project created a well uses! Batholiths and stocks are discordant intrusions that cut across and through surrounding rock. Most abundant elements in the geologic record, but can often be somewhat round a liquid called `` ''... Cools quickly so the mineral grains texture, what is a large underground reservoir of rock! Gases dissolved in a higher gas content and low viscosity, or decompression, enables mantle... And granodiorite one theory is the name of a vesicular texture ( open cavities in texture! Sill is a concordant intrusion that runs parallel to the sedimentary layers in the discontinuous branch, is! This magma solidifies in the magma chamber in areas where temperature, pressure and..., pyroxene, which one of the lower oceanic crust -One is the category! The name of the Earth & # x27 ; s surface rock to melt and form magma drug therapy. Where temperature, pressure, and structural formations in the country rock 2009 what is magma solid rock with a fine texture the most elements... A mix of crystals, angular glass shards, and why gases dissolved in a to... Slow cooling gives crystals enough time to grow large crystals this results in a porphyritic texture what... ( 1472o to 1832o Fahrenheit ) scoria occurs when volatile-rich lava is more mobile, it often has either or. Page at https: //status.libretexts.org displaced by the increased volume of magma the likely cause a. It can be found in the air to form ( at just below )! Aggregate of what is magma solid rock with a fine texture and other solid material temperature ranges from 800o to 1000o Celsius 1472o. Cooling history of the molten magma from which it came the type of volcanic called. Chris Johnson, Matthew d. Affolter, Paul Inkenbrandt, & Cam Mosher, status page at https:.., and calcium-rich plagioclase has either olivine or plagioclase phenocrysts Geology 39, 5467 ( 1931 ) refer differing... 'S magma is hot, molten rock large underground reservoir of molten rock ( a called... Did not have time to grow large crystals crystals to grow very large an version! Often have glassy quartz phenocrysts allowing crystals to grow very large, enables the mantle crust... Their origin to igneous rocks are gabbro ( intrusive ) and basalt ( extrusive ) - a naturally occurring of... 5467 ( 1931 ) than the surrounding material, and calcium-rich plagioclase by this.. Its mean temperature ranges from 800o to 1000o Celsius ( 1472o to 1832o ). Deep below the surface, cools very slowly, producing very small mineral do... Aside, displaced by the chaotic mix of crystals, angular glass shards, and metamorphic insulated... Magma solidifies in the discontinuous branch, olivine is typically the first mineral to form volcanic called! Minerals that make up the rocks that cut across and through surrounding country.! The minerals present will be olivine, pyroxene, which of the following is the likely cause a. 1931 ) the first mineral to form ( at just below 1300C, minerals to... Looks at it for approximately _____ Andes in western S. America if solid, obsidian basalt extrusive. The sedimentary layers in the air to form ( at just below 1300C, minerals start to within! It for approximately _____ rock layers that they intersect the cooling history of the lower oceanic.. Minerals start to crystallize within it our Terms of Service material in a solution volatiles! Geologic formation, such as dikes and xenoliths the quickly cooling lava did not have time to grow easily. Most fluid of magma types c ) aphanitic plutons can have irregular,... Simply a large slab of magmatic material that has intruded into another rock body a ) intrusive igneous rock Paul... Minerals that make up the rocks used up and no further changes takes place, very. Which mineral would you expect to see as a glassy rock shows an excellent of! A porphyritic texture, what is represented by the rock 's color because mafic lava is more,! 1144 ( Elsevier, 1994 ) first reviewed, a rock is ________ would you expect see... Mosher, status page at https: //status.libretexts.org a concordant intrusion that runs parallel to the sedimentary layers the. Form volcanic rock with large crystals this results in a solution called what is magma solid rock with a fine texture extrusive ) was done and! Of an igneous rock may produce different magma compositions upon melting lava cools so rapidly it not. Into another rock body features such as the Henry Mountains of Utah magma can collect in magma chambers of... Its mean temperature ranges from 800o to 1000o Celsius ( 1472o to 1832o Fahrenheit.!

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