Which magma is more viscous quizlet? Because mafic lava is low viscosity, when it erupts from a volcano it flows downslope away from the vent, gradually cooling and crystallizing. Volcanoes are one of the most fascinating phenomena that grace Earths surface; they are the windows into the nether region, a brief glimpse into the underlying processes governing our world. Most of the igneous rocks can be classified as Mafic or Felsic. Source: Physical Properties of Magma It is of importance that the magma viscosities can be calculated. Mafic lava forms basalt and is associated with the lava flows seen on the Hawaiian Islands and similar shield volcanoes. Where tectonic plates come together, volcanoes often have thicker, viscous magma with high gas content. Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. Exercise 3.3 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. The higher the amount of silica in the magma the higher is its viscosity. Low viscosity means that mafic magma is the most fluid of magma types. The mafic magma is rich in magnesium and iron which causes its dark color. What are Mafic and Felsic Rocks? Consequently, a main finding from the compilation of data on mafic melts is that their viscosity converge to a value of 20-30 mPa s by 13 GPa for all melts compositions documented in Figure 3 at the exception of the MgSiO3#1 for which a slight albeit discernable viscosity increase is observed above 7 GPa. 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. These are generally of three main types which include igneous rocks, sedimentary rocks, and metamorphic rocks. On the basis of the texture of the rocks, different names of mafic rocks can be there. Mafic magma has less silica content and more iron and magnesium in it. Experimental results of mineral growth in magmas. Mafic rocks are denser and heavier than Felsic rocks. The higher the amount of silica in the magma, the higher is its viscosity. Working mostly with basaltic magmas, he determined the order of crystallization of minerals as the temperature drops. This is because of the fact that minerals that make up these igneous rocks contain iron and magnesium. Viscosity describes a fluid's resistance to flow, or how thick or sticky the fluid is. Typical intermediate rocks are diorite and andesite (Figure 3.13). the importance and affect of magma viscosity (how thick it is) in magma movement and shape of whatever structure is formed. This type of magma has a high gas and silica content. A. The rock will have some relatively large crystals (phenocrysts) of the minerals that crystallized early, and the rest will be very fine grained or even glassy. . GAS: In a volcano with low silica content gas escapes easily from the surface of the lava. Mafic magma is not viscous and will flow easily to the surface. Felsic magmas can erupt at temperatures as low as 650 to 750 C. This process is known as fractional crystallization. If that magma is then involved in a volcanic eruption, the rest of the liquid will cool quickly to form a porphyritic texture. Since felsics tend to cap steam and other gases, explosive eruptions are more likely. The name is derived from the Andes Mountains, as it is a commonly found rock among the mountain chains stratovolcanoes. The amount of silica influences the magma's viscosity in such a way that if the silica content is low the magma would have low viscosity whereas a high content of silica would make the magma more thick and sticky. Viscosity generally increases as the temperature decreases. This topic will be helpful to understand one of the types of igneous rocks which are formed from magma and which we usually study in Geography, Geography, Earth Sciences, Physical Geography, etc. Explosive eruptions happen along the edges of continents and produce tremendous amounts of material ejected into the air. Felsic magmas, on the other hand, have much more SiO2 (65% to 75%) and Na2O + K2O (around 10%) and much less FeO and MgO plus CaO (about 5%). What is the relationship between the silica content of magma and the explosiveness of a volcanic eruption? A number of processes that take place within a magma chamber can affect the types of rocks produced in the end. Another characteristic feature of Mafic rocks is that they are dark in color and have a high density. Difference Between Mafic and Felsic: Conclusion. Among these factors, magma viscosity should be one of the most important, because the viscosity determines whether a dike (magma-filled crack) can be propagated with a high enough ascent velocity to overcome solidification [e.g., Rubin, 1995]. The higher the amount of silica in the magma the higher is its viscosity. Mafic is a term used to describe the densest lava flows. Which magma is more viscous quizlet? Mafic magma is not viscous and will flow easily to the surface. What is the viscosity of magma? Mafic is a kind of igneous rock which are rich in magnesium and iron. Required fields are marked *. Hawaiians worshiped volcano gods; Pliny the Younger reverently documented the destruction of Pompeii. The anomalous viscosity decrease appears to be a universal behavior for magmas up to 13 GPa, while the P dependence of viscosity beyond this remains to be measured. As the temperature drops, and assuming that some silica remains in the magma, the olivine crystals react (combine) with some of the silica in the magma (see Box 3.1) to form pyroxene. The composition of the original magma is critical to magma crystallization because it determines how far the reaction process can continue before all of the silica is used up. Thus, it is clear that these igneous rocks are rich in magnesium and iron. The magma slows down. What do You Mean by Mafic Rocks? Mafic rocks are darker in color than Felsic rocks. Magma viscosity varies, with temperature, water content, and composition, between about 102 Pa s and about 1011 Pa s. What happens when the lava that flows during volcanic eruption has less silica content? Additionally, they contain somewhat more gas than do the ultramafic magmas, but not nearly so much as the felsic magmas. Because the mafic rocks are enriched in Fe and Mg, they tend to be darker colored than the felsic rock types. Water and other volatiles can more easily and gradually escape from mafic lava. What is mafic magma? Intermediate-composition magmas will crystallize to produce the rock andesite. Science. Earth Sciences. Magmas that have a high silica content will therefore exhibit greater degrees of polymerization, and have higher viscosities, than those with low-silica contents. These are terms that are used by geologists to describe igneous rocks based upon their silica content. The volcanic eruptions consist of mafic lava are less explosively violent as compared to felsic volcanic eruptions. Terms of Use and Privacy Policy: Legal. How does the viscosity of magma change as magma cools? For all compositions, viscosity decreases with P, rapidly below 5 GPa and slowly above. If rock formation is done below the surface of the Earth is known as intrusive igneous whereas if it occurs above the surface of the Earth, it is known as Extrusive rocks. Poorer in aluminum and silica than . At that temperature, the plagioclase is calcium-rich (anorthite) (see Figure 2.15). The viscosity of magma increases with: high % silica and cooler temperatures. 3. Question: Question 16 (1 point) Viscosity is function of temperature and composition, so which . About the Author: Admin Answer. Lava contained within the Earths crust is known as magma; rock that has been liquefied due to the intense pressure and heat within the mantle. Felsic magma or lava is higher in viscosity than mafic magma/lava. Olivine, pyroxene, amphibole, and biotite are common rock-forming minerals of mafic. About & Disclaimer | Terms | Privacy | Contact, What is the Difference between Lava and Magma. The Earth, by weight, mostly consists of mafic or ultramafic rocks, but silicic rocks are considered to be more abundant on the surface of the Earth. Intermediate Magma . - Collins Dictionary. Mafic magmas are low in silica and contain more dark, magnesium and iron-rich mafic minerals, such as olivine and pyroxene. Answer and Explanation: The two main factors that affect how viscous lava is are the mineral content of the lava and its temperature. The higher the amount of silica in the magma, the higher is its viscosity. Differences in a magmas viscosity will determine the shape a volcano takes. When we divide the igneous rocks on the basis of silica content, mafic rocks stand at 3rd rank in terms of it i.e 45 to 55% silica content and they are dark colour rocks in which most common mafic minerals are Olivine, pyroxene, amphibole, and biotite. Mafic lava before cooling has a low viscosity in comparison with felsic lava due to the lower silica content in mafic magma. The Earth, by weight, mostly consists of mafic or ultramafic rocks, but silicic rocks are considered to be more abundant on the surface of the Earth. Mafic magma also has high mean temperatures, between 1000o and 2000o Celsius (1832o and 3632o Fahrenheit), which contributes to its lower viscosity. Mafic magmas produce effusive eruptions. The compositions of typical mafic, intermediate, and felsic magmas are shown in Figure 3.12. Chapter 6 Sediments and Sedimentary Rocks, Chapter 7 Metamorphism and Metamorphic Rocks, Chapter 21 Geological History of Western Canada, http://en.wikipedia.org/wiki/File:NormanLBowen_1909.jpg, Next: 3.4 Classification of Igneous Rocks, Creative Commons Attribution 4.0 International License. Mafic magma often has a relatively low gas content and so usually erupts in a non-explosive or mildly explosive. When viscosity is low, flow rate (velocity) is high. In the discontinuous branch, olivine is typically the first mineral to form (at just below 1300C). Rocks are said to be the hard matter which forms after the solidification of the magma and because of various other geographical phenomena. ( Geology ). The common type of mafic rocks is basalt, pyroxene, biotite, etc. These differences cause lower viscosity (more "runny") and darker color than felsic magma. Answer. Mafic is an acronym made up of Ma that stands for Magnesium and Fic that stand for iron or ferric, the Latin name of iron. The type of lava emitted in an eruption can reveal intimate details of the inner workings of not only the volcano, but also the underlying geological processes governing Earths surface. These terms are also used while talking about the characteristics of lava. It commonly occurs at divergent plate boundaries, hot spots, and convergent plate boundaries. Viscosity of Magmas Viscosity is the resistance to flow (opposite of fluidity). The results were studied under the microscope and by chemical analysis. On this basis, igneous rocks can be divided into four major types i.e felsic, intermediate, mafic, and ultramafic ( written as per the silica content in decreasing order). It is the dominance of these lighter elements in these rocks that makes them lower in density. The examples of the former rock are gabbro, basalt, etc and of the latter are rhyolite, granite, etc. Physical Geology by Steven Earle is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted. We can think of things like syrup or in this case honey.More. 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. 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. This type of rock contain 45 to 55 % silica content and 4 mafic igneous rocks minerals are pyroxene, amphibole, olivine, and mica. At about the point where pyroxene begins to crystallize, plagioclase feldspar also begins to crystallize. As silica content increases, viscosity increases. Mafic rocks are rich in iron and magnesium, whereas Felsic rocks are rich in silica and aluminum. Intrusive and Extrusive. Describes magma that contains lower amounts of silica and is generally less viscous and less gas-rich than silicic magma. This occurs when calcium-rich early-forming plagioclase crystals become coated with progressively more sodium-rich plagioclase as the magma cools. The silica content of the magma determines how thick the magma is, how easily it flows and how easily dissolved gases within the magma can escape; therefore the silica content determines the characteristic of the volcanic eruption and the shape and size of the resulting volcanic cone. The liquid does not move much. Felsic magma is viscous and does not flow easily. Viscosity is a measure of a liquid's resistance to flow. The most common examples of rocks classified as Mafic are gabbro, dolerite, and basalt. Mafic Magma (Balsatic) Mafic magma, on the other hand, has a low viscosity and mafic eruptions tend to be less violent due to the ability of water and other volatiles to escape more easily. . It is the silica content that controls the viscosity of the magma, and hence the nature of the volcanism that is seen. What happens to the viscosity of magma when the temperature increases? @media (max-width: 1171px) { .sidead300 { margin-left: -20px; } } Mafic magma tends to have _____ viscosity, while felsic magma tends to have _____ viscosity. How is felsic magma formed? Tends to erupt effusively, as lava flows. If the magma has a low viscosity (i.e., it's runny) which is likely if it is mafic the crystals that form early, such as olivine (Figure 3.14a), may slowly settle toward . If we talk about Igneous rocks, these are formed after the solidification of magma and can be of two types i.e. 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 3.14c). (The values are similar to those shown in Figure 3.12.). This topic is useful to study whenever we talk about igneous rocks and their types. Describe magma with a high viscosity. Low viscosity means that mafic magma is the most fluid of magma types. The term roughly corresponds to the older basic rock class. Felsic magmas are higher in silica and have lighter colored minerals such as quartz and orthoclase feldspar. In turn, felsic magma is associated with the volatile stratovolcano characterized by Plinian eruptions (mushroom cloud) followed by a deadly pyroclastic flow of hot ash, gas, and lava. The magnitude of the viscosity decrease is larger for pyroxene melts than for fayalite melt and larger for the Ca end-member within pyroxene melts. Felsic is a term that is made up of the names of Feldspar and silica. How does the silica content affect the behavior of magma? What is the process of minerals crystallizing and evolving mafic compositions into intermediate felsic compositions? Felsic magmas are higher in silica and contain lighter colored minerals such as quartz and orthoclase feldspar. Silica is the most abundant material found in igneous rocks. "It is Relating to or denoting a group of dark-coloured, mainly ferromagnesian minerals such as pyroxene and olivine and often contrasted with felsic. Magma with a high viscosity is cooler in temperature, has a high amount of silica, and is Granitic/Andesitic. Although there are many exceptions to this trend, mafic magmas typically have 1% to 3% volatiles, intermediate magmas have 3% to 4% volatiles, and felsic magmas have 4% to 7% volatiles. High-silica (basalt) magma has a much lower viscosity. Just as different solids such as ice or chocolate have different melting points, so do different rock types. Of the common silicate minerals, olivine normally crystallizes first, at between 1200 and 1300C. "Mafic describes rocks containing more dark-coloured substances and iron than other rocks." Because of the depth, it is hotter and contains more high density materials, such as iron and magnesium. Mafic magma is a close kin to basaltic magma, having a silica content of roughly 50 percent and temperatures of 1,832 to a blistering 3,632 degrees Fahrenheit. Describe magma with a high viscosity. [image from Wikipedia: http://en.wikipedia.org/wiki/File:NormanLBowen_1909.jpg]. Mafic magma will cool and crystallize to produce the volcanic rock basalt , whereas felsic magma will crystallize to produce dacite and rhyolite. As a mafic magma starts to cool, some of the silica combines with iron and magnesium to make olivine. What is the difference between mafic and felsic? Mafic magma has a low content of silica because of which before cooling, mafic lava has a low viscosity. For an introductory college-level earth sciences class: a review of the impacts of magma viscosity on how crystals form underground and how, above ground, la. Mafic magma has a low content of silica because of which before cooling, thus, mafic lava has a low viscosity. 1. 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. Common examples of mafic rocks are basalt, CBSE Previous Year Question Paper for Class 10, CBSE Previous Year Question Paper for Class 12. The common type of mafic rocks is basalt. Felsic magma can evolve from mafic magma. Igneous rock may also be transformed into metamorphic rock, and metamorphic rock exposed at Earth's surface may be eroded to produce sediment. Most of these rocks are gray though Mafic rocks are also found in brown, green, and even black colors. Using the diagram shown here, predict what phenocrysts might be present where the magma cooled as far as line a in one case, and line b in another. Eruptions of mafic magma are quick and lack the explosiveness of higher silica types. How does temperature and silica content affect the viscosity of magma? A magma with high silica (>60%) will be quite viscous and so the eruption will be violent. The amount of gases dissolved in the magma determines the explosiveness of eruptions. Felsic magma has more silica and alumina content, which makes magma more viscous. It is not just silica and aluminum, but these rocks are also rich in oxygen, potassium, and sodium. In cases where cooling happens relatively quickly, individual plagioclase crystals can be zoned from calcium-rich in the centre to more sodium-rich around the outside. Earth Sciences questions and answers. The early-forming olivine crystals react with silica in the remaining liquid magma and are converted into pyroxene, something like this: olivine pyroxene, This continues down the chain, as long as there is still silica left in the liquid. Mafic and felsic rocks are both an important type of igneous rocks which are being classified on the basis of silica content present in them. In a third mechanism, cooling and partial crystallization of mafic magma when . [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Or "( Geology ) of or pertaining to igneous rocks that are rich in dark-coloured minerals and that contain magnesium and iron and a comparatively low level of silica." What will increase the flow of magma? Some of the standard definitions are given below: "In Geology, of or relating to rocks rich in dark, ferromagnesian minerals." Humankind has been diligently documenting and studying volcanoes for millennia in an attempts to understand volcanoes. It turns into basalt when it cools. What is mafic magma? Question2. Mafic rocks are darker in color than Felsic rocks. Non-explosive eruptions produce lavas, such as a'a, pahoehoe, and pillow lavas. Your email address will not be published. Heating reduces viscosity (warm syrup flows more easily than cold.) Most felsic magma will stay deeper in the crust and will cool to form igneous intrusive rocks such as granite and granodiorite. At the moment, magma fragmentation mechanisms and efficiency in low viscosity, mafic systems are poorly quantified, although the role of magma vesicularity (in terms of bubble size distribution 22 . How does silica affect viscosity? And yes, it is true that felsic magma is more viscous than mafic magma yet less dense. Difference Between Coronavirus and Cold Symptoms, Difference Between Coronavirus and Influenza, Difference Between Coronavirus and Covid 19, What is the Difference Between Vibrational Relaxation and Internal Conversion, Difference Between Transfer Paper for Light Shirts and Dark Shirts, Difference Between Doberman and Doberman Pinscher, Difference Between Glioma and Glioblastoma, Difference Between Reversible and Irreversible Cell Injury, What is the Difference Between Upper and Lower Gastrointestinal Bleeding, What is the Difference Between Pockels Effect and Kerr Effect, What is the Difference Between GLUT2 and GLUT4, What is the Difference Between Monoprotic and Diprotic Acid, What is the Difference Between Hermetic and Non-hermetic Packaging. Mafic magmas are low in silica and have darker magnesium and iron-rich mafic minerals, such as olivine and pyroxene. Tends to erupt effusively, as lava flows. If the magma cools slowly underground, the product will be gabbro; if it cools quickly at the surface, the product will be basalt (Figure 3.13). How does viscosity affect the movement of magma? These low temperature lava flows have a high viscosity, which clogs the inner workings of volcanoes trapping and compounding gases. Felsic magma is viscous and does not flow easily. The style of a volcanic eruption depends on magma viscosity. Its temperature is between 1472 to 1832 Fahrenheit resulting in a higher viscosity than mafic magma. The thicker magma is, the higher the viscosity. Viscosity is determined by its composition and temperature: Felsic lava is more viscous than mafic lava. Common examples of mafic rocks are basalt, gabbro, diabase, etc. Question 16 (1 point) Viscosity is function of temperature and composition, so which magma would have the highest viscosity (least likely to flow)? 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. Three physical situations can be identified: (a) where the mafic magma remains less viscous than the silicic magma; (b) where the mafic magma becomes . As the temperature continues to drop, olivine becomes unstable while pyroxene becomes stable. 2017 Actforlibraries.org | All rights reserved Faster fluids have low viscosity. A short violent relatively small explosion of viscous magma.
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