The mafic magmas are somewhat more viscous than the ultramafic magmas, but they are still fairly fluid. Therefore, rocks are divided into ultramafic, mafic, intermediate, and felsic. Additionally, they contain somewhat more gas than do the ultramafic magmas, but not nearly so much as the felsic magmas. Viscosity determines what the magma will do. Many students confuse between the two adjectives Mafic and Felsic. mafic (silica content) low silica. e) This is a correct statement. Question 33 of 50 0.0/ 2.0 Points Volcanic rocks are the primary formations studied in order to reveal new geological facts. Mafic lava creates basalt while felsic lava produces andesitic and rhyolite rocks. This is an order showing increased silica content. Mafic lava leads to weaker volcanic eruptions. • Mafic rocks are darker in color than Felsic rocks. • Lava made up of Felsic rocks is slow moving and has a higher viscosity than Mafic lava. Quartz, muscovite mica, orthoclase and sodium-rich plagioclase feldspars. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Made up of only 50% silica, the silica content of mafic magma is considered very low. Silica content. Thus, rocks having more than 65% of silica are Felsic while those having 45-55% of silica are classified as Mafic rocks. Felsic minerals are usually light in color and have specific gravities less than 3.0. felsic vs. mafic. Common felsic minerals include quartz, muscovite mica, and the orthoclase feldspars. Silica content! All Felsic rocks contain a high percentage of silica. These are igneous rocks that have a lower density than mafic rocks and are also lighter in color. Within this scheme, rocks are described as felsic, intermediate, mafic, and ultramafic (in order of decreasing silica content). Because oxygen and silicon are by far the two most abundant elements in magma, it is convenient to describe the different magma types in terms of their silica content (SiO2). Felsic lava (silica-rich; example: rhyolite) has high viscosity (think silly putty), and leads to explosive eruptions, where bursting gas bubbles fragmentlava and eject it (and other materials). It depends on the chemical composition, temperature and viscosity of the Felsic and Mafic melt. The higher the amount of silica in the magma, the higher is its viscosity. It is the dominance of these lighter elements in these rocks that makes them lower in density. The term acid rock, although sometimes used as a synonym, in current usage refers to a high silica content (greater than 63% SiO 2 by weight) volcanic rock such as rhyolite. The felsic end is lighter due to the preponderance of the more lightly hued silica. Mafic rocks are low in silica content compared with intermediate and felsic rocks. These are terms that are used by geologists to describe igneous rocks based upon their silica content. granite, right.) Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. On the other hand, Felsic has much higher levels of silica. 5. 2.Mafic lava is predominant in mid-ocean ridges while felsic is primarily located at convergent zones. It was once thought that silicic acid was the dominant form of sili-con in rocks (this is not the case), so the term acidic is some-times also used as a synonym of felsic. Because of the high viscosity, intermediate magma builds up in magma chambers below the surface before exploding violently as lava. This, in turn, would lead to rapid explosive ejection of the gas bubbles. Mafic and felsic are terms to describe, both visually and chemically, the silica content of an igneous rock. The properties of these volcanoes, the characteristics like temperature, ash content, composition of elements in magma, etc., determine the shapes or forms of volcanic formations on solidification. Like felsic magma, however, intermediate magma is very thick and very gooey, and its mean temperature is usually between 1472ᵒ to 1832ᵒ Fahrenheit, making it much hotter than felsic magma. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. The temperatures are around 650°C to 750°C. Silica content. Independent Tetrahedra. Discover the activities, projects, and degrees that will fuel your love of science. The term comes from FEL for feldspar (in this case the potassium-rich variety) and SIC, which indicates the higher percentage of silica. Crystalline and amorphous are two basic sub-types of solids, which may look similar on the outside, but are actually vastly different from the inside. Felsic magma is paler than mafic, and generally results from the melting of crustal material. Well, we're looking for good writers who want to spread the word. This is why silica content has been chosen to classify igneous rocks with higher silica content making a rock Felsic while lower silica content making them Mafic. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks have a much higher proportion of silica (>63%) Mafic rocks have a lower proportion of silica (20-40%) Pretty much all differences in the characteristics of the 2 rock groups are caused by this difference; colour, nature of eruptions, melting point, etc etc. • Mafic rocks are denser and heavier than Felsic rocks. Much higher levels of silica and aluminum, but not as high magnesium or iron levels as found in,. 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