Xenoliths are rock fragments broken from the magma chamber or conduit walls. A) texture Granite is a course-crystalline felsic intrusive rock. As with dikes, sills are younger than the surrounding layers and may be radioactively dated to study the age of sedimentary strata. Andesitic rocks are often found at continental volcanic arcs, such as the Andes Mountains in South America, after which they are named. 4. pillow basalt, __________ composition lava is erupted at ocean ridges, whereas ____________ composition lava is erupted on continents. C. basalt light colored, less dense and more viscous (sticky) If no button appears, you cannot download or save the media. 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. Decompression MeltingDecompression melting involves the upward movement of Earth's mostly-solid mantle. D. andesite 20/3 Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Its mean temperature ranges from 800o to 1000o Celsius (1472o to 1832o Fahrenheit). Because mafic lava is more mobile, it is less common than basalt. D. plate tectonics, Match the appropriate term associated with the production of magma to its best description. Mafic rocks/magmas are ________, whereas felsic rocks/magmas are ________. A) the magma heats up and ions in crystals break their bonds due to expansion and Si and O ion vibration Note that, unlike Figure 3.2.1, these compositions are expressed in terms of oxides (e.g., Al2O3 rather than just Al). Differences in temperature, pressure, and structural formations in the mantle and crust cause magma to form in different ways. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Texture describes the physical characteristics of the minerals, such as grain size. The rock then cools into new crust. 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. = 15 * 3/20 C) gabbroic For example, it is not known what happens to the pre-existing country rock as the diapir intrudes. C) Pegmatite It is poor in silica, in the 40% or less range. A. peridotite Igneous rocks are classified based on texture and composition. Whenever an individual stops drinking, the BAL will ________________. Are plutons assembled over. Granite is a good approximation for the continental crust, both in density and composition. Match the igneous rock texture and its appropriate description. A) diorite; intrusive rock that formed from the cooling of relatively intermediate silica magma In the discontinuous branch, olivine is typically the first mineral to form (at just below 1300C). C. aphanitic or glassy texture Because mafic lava is more mobile, it is less common than basalt. Stage 2 Which mineral would you expect to see as a, Which of the following igneous rocks exhibit aphanitic texture? Intermediate MagmaIntermediate magma has higher silica content (roughly 60%) than mafic magma. Granite: Granite is the intrusive equivalent of rhyolite but has a coarser texture. What is a likely reason for this phaneritic texture? [Hint] Typical intermediate rocks are diorite and andesite. This magma solidifies in the air to form volcanic rock called tephra. 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. C) rate of cooling Andesite is a fine crystalline intermediate extrusive rock. This section will focus on the common igneous bodies which are found in many places within the bedrock of Earth. Granite commonly has large amounts of salmon pink potassium feldspar and white plagioclase crystals that have visible cleavage planes. Arndt, N. T. Chapter 1 Archean Komatiites. 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 . Gases, ash, and light-colored rock are emitted first, from the least-dense, top layer of the magma chamber. Weegy: 15 ? Rocks that solidify from lava flows are typically finer grained than those that crystallize intrusively. C) The extrusive magma cools quickly so the mineral grains do not have time to grow. = 15 ? b. 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. This results in a higher gas content and viscosity. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. Pegmatite is much coarser in grain size compared to most coarse-grained igneous rocks. 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. Rhyolite is a fine-crystalline felsic extrusive rock. When it cools to solid rock, this intrusion is often called a pluton. 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. 6. andesite, Match the rock type with the appropriate description. A) considered "volcanic" rocks because they form from magma beneath the surface; considered "plutonic" because they form from lava erupted from a volcano. The minerals that make up igneous rocks crystallize at a range of different temperatures. Mafic magmas have 45% to 55% SiO2, about 25% total of FeO and MgO plus CaO, and about 5% Na2O + K2O. The Bowen reaction series is one of the results of his work, and even a century later, it is an important basis for our understanding of igneous rocks. Arndt, N. T. Chapter 1 Archean Komatiites. D. ions vibrate so much that the vibrating breaks some of the chemical bonds, What process (or processes) can aid in generating magma from solid rock? The Rights Holder for media is the person or group credited. It is commonly vesicular and aphanitic. Diorite is a coarse-crystalline intermediate intrusive igneous rock. 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). 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. 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). The black colors are likely two or three different minerals. In fact, magma has only been discovered three times in its natural habitat deep in Earths crust. cooled rock with large crystals Which are definitions of "mafic" and "felsic"? B) the first crystals to form when the magma was in the magma chamber Because felsic lavas are less mobile, it is less common than granite. A) granite Introduction to Igneous Rocks. These trapped bubbles can cause explosive and destructive eruptions. Mysterious MagmaMagma is usually studied as lava or igneous rock. 1: Granite is a classic coarse-grained (phaneritic) intrusive igneous rock. Learn how BCcampus supports open education and how you can access Pressbooks. The least-dense magma rises to the top. 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. The type of volcanic rock with common vesicles is called scoria. These differences in chemical composition are directly related to differences in gas content, temperature, and viscosity. D) solid + crystal. A) Mafic is a magma/rock that is rich in feldspar and silica (quartz), whereas felsic refers to that which is rich in Fe and Mg. This huge increase in temperature allowed just one magma well to generate roughly 36 megawatts of electricity, powering 36,000 homes. B. basalt Because of this, dikes are often vertical or at an angle relative to the pre-existing rock layers that they intersect. These tiny crystals can be viewed under a petrographic microscope [1]. Pyro, meaning fire, refers to the igneous source of the tephra and clastic refers to the rock fragments. solid rock with a fine texture 3.5 Igneous Rocks Charlene Estrada. A) the rock's texture 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. 1 minute molten rock below Earths surface These rocks are rare on the surface, but make up peridotite, the rock of the upper mantle. Volcanic glass and coarse-grained igneous rocks differ by which of the following? The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix. Classification of Igneous Rock Series. 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. 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). 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. Lava cools to form volcanic rock as well as volcanic glass. d. B. The process by which the same igneous rock may produce different magma compositions upon melting. Texture describes the physical characteristics of the minerals, such as grain size. If vesicular, pummus geothermal gradient It can be found in the Andes Mountains and in some island arcs (see. Figure 3.3.1, 3.3.4, 3.3.5, 3.3.6, 3.3.7, 3.3.8: Steven Earle. C) the magma in the magma chamber before eruption A) the lava after it erupted from a crystallizing magma chamber solid and pinstriped A) the rock's texture Dark, dense volcanic rock from the lower part of the magma chamber may be released later. . D) The extrusive magma cools quickly so the mineral grains do not have time to grow any larger. Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. D) rhyolitic, What type of composition would result in a magma if basaltic and granitic composition magma were mixed completely at a 1 to 3 ratio? As the temperature continues to drop, olivine becomes unstable while pyroxene becomes stable. When porphyritic, it often has either olivine or plagioclase phenocrysts. C) basalt; extrusive rock that formed from cooling of relatively high silica lava An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. Thick, viscous felsic magma can trap gas bubbles in a volcanos magma chamber. It has also been proposed that diapirs are not a real phenomenon, but just a series of dikes that blend into each other. In either of these situations, the magma that has moved toward the surface is likely to cool much faster than it did within the magma chamber, and the rest of the rock will have a finer crystalline texture. Komatiite is a rare rock because volcanic material that comes directly from the mantle is not common, although some examples can be found in ancient Archean rocks [2]. A. rhyolite In a porphyritic texture, what is represented by the rock's "groundmass"? 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. Rhyolite is commonly pink and will often have glassy quartz phenocrysts. An extrusion could include lava and volcanic rock. Transfer of heat often happens at convergent boundaries, where tectonic plates are crashing together. B) gabbroic, rhyolitic A) highly viscous, cools slowly Note that these 8 elements make up about 99 percent of the Earth's crust. D) peridotite, Most magmas are dominantly molten rock (a liquid called "melt"). Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. If the fragments accumulate while still hot, the heat may deform the crystals and weld the mass together, forming a welded tuff. Which of the following best describes an aphanitic texture? 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. quartz and pyroxene If a magma chamber encounters an enormous amount of pressure, however, it may fracture the rock around it. F) Both c. and d. Please select the best answer from the choices provided C) Pressure of the environment - higher P = slower magma cooling. Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. They have a mineral composition that is intermediate between granite and basalt. B. heat expansion of the ions breaks apart the crystalline solid A xenolith is a piece of rock trapped in another type of rock. D) pressure. Laccoliths are blister-like, concordant intrusions of magma that form between sedimentary layers. As it falls to Earth, tephra includes rocks such as pumice. Comments Areas of lower pressure always have a lower melting point than areas of high pressure. C. Mt. D) Both a. and c. America. Extrusive igneous rocks are _________, whereas intrusive igneous rocks are _________. At that temperature, the plagioclase is calcium-rich (anorthite) (see Figure 2.6.1). Coarse-grained textures generally indicate magmas that slowly cooled deep underground. E. phaneritic texture, relatively high silica content The solid parts, called tephra, settle back to earth and cool into rocks with pyroclastic textures. Magma is like seltzer: It contains "Volatile gases" - H2O, CO2, SO2, N2, CH4and other dissolved gases. 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). D) texture and mineral composition B. the upper mantle 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. Each of these rocks are formed by physical changessuch as melting, cooling, eroding, compacting, or deforming that are part of the rock cycle. What does it mean if a rock has a coarse texture? B) Each vesicle was filled by a crystal when the lava was mostly solid, and the crystals fell out later. [Hint] Mafic describes a kind of igneous rock or even magma that is relatively high in magnesium and iron content; hence the word 'mafic' which is a combination of the words magnesium and ferric . The solid parts, called tephra, settle back to earth and cool into rocks with pyroclastic textures. F. olivine D) the rock's density, The most important factor affecting the texture of an igneous rock is ________. As long as more magma pools into a volcanos magma chamber, there is the possibility of an eruption and the volcano will remain active. B) basalt Sedimentary rocks are formed from pieces of other existing rock or organic material. 15-30 seconds 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? D) granite; intrusive rock that formed from cooling of relatively intermediate silica magma A) rhyolitic Magma can intrude into a low-density area of another geologic formation, such as a sedimentary rock structure. A sill is a concordant intrusion that runs parallel to the sedimentary layers in the country rock. The Henry Mountains of Utah are a famous topographic landform formed by this process. = 45/20 Magma that has cooled into a solid is called igneous rock. Pyroclastic texture is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments. Gabbro is a coarse-grained mafic igneous rock, made with mainly mafic minerals like pyroxene and only minor plagioclase. B) the rock's composition 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. D) komatiite F. lower silica, high iron and magnesium, aphanitic texture D. Thin sections are thick slices of rocks that allow light to pass through them so sunlight may be used to study them. Igneous rocks contain information about how they originate. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. B) Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. User: 3/4 16/9 Weegy: 3/4 ? 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. This texture, which indicates a very slow crystallization, is called pegmatitic. An igneous rock with large crystals embedded in a matrix of finer crystals is indicative of a two-stage cooling process, and the texture is porphyritic (Figure 3.15).