This lab deals with the aspects and factors that affect magma / lava viscosity. Definition. It is a type of magma that hardens quickly once it reaches the surface. Expansion of gas bubbles is resisted by high viscosity of magma - results in building of pressure; High pressure in gas bubbles causes the bubbles to burst when reaching the low pressure at the Earth's surface. Because of their lower temperature and high silica content granitic magmas tend to be highly viscous (linked domains of silica tetrahedra), whereas basaltic magmas are of low viscosity (much more fluid), and are able to flow (Hawaii). This type of magma has a low gas content and low viscosity, or resistance to flow. ... Hawaii. Do composite volcanoes have high silica? Altiplano-Puna Magma Body Most basaltic magma rises relatively rapidly to Earth's surface and reacts very little with crustal rocks because of it's low viscosity. SEM images show natural-like mixing textures whereas microprobe analyses reveal concomitant basalt melting and mixing producing andesitic melts. Volcanoes and Lahars It usually erupts with thin flows of lava very quietly. The small- to moderate-volume, Quaternary, Siwi pyroclastic sequence was erupted during formation of a 4 km-wide caldera on the eastern margin of Tanna, an island arc volcano in southern Vanuatu. This high-potassium, andesitic eruption followed a period of effusive basaltic andesite volcanism and represents the most felsic magma erupted from the … High-viscosity, silicon-rich andesites are much less fluid than basalt and are erupted at temperatures of around 700–900°C. The formation of the rock when gases in the magma expand to form bubles as lave reaches the surface.The bubbles are then retained as the lava solidifies. rhyolitic volcanoes characterized by their small to moderate size, high magma viscosity, steep flanks and low to moderate volatile content. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Basalt A volcanic rock consisting of less than 53% silica with a low viscosity when in a molten state. Mafic magma also has high mean temperatures, between 1000 o and 2000 o Celsius (1832 o and 3632 o Fahrenheit), which contributes to its lower viscosity. A. Fe and Mg C. K and Na B. Mg and Ca D. Na and Hg 3. volcano, shield, strato type, composite This fragmentation condition is applicable to low-viscosity (crystal-poor) mafic magmas, where fragmentation is most likely to be controlled by inertia. These andesitic melts also have a high water content (~7-10 wt.% water) indicated by the high electrical conductivity measured in the APMB. Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma). Andesitic magma C) low viscosity and flows quickly. Magma (Characteristics, Types, Sources, and 0 plays. Andesitic magma erupts explosively since it tends to have high gas content. The top of a lava flow is made up of a highly vesicular, rubbly material known as scoria. Silicic magmatic compositions and fast cooling rates prevent the formation of crystals even at the microscopic scale. magma In other words, as magma cools, its viscosity increases. Magma Low Viscosity magma. Magma (c) a low silica content and high temperature. However, if the magma is viscous, like rhyolite, its high polymerization will impede the upward mobility of the gas bubbles. in Fe, Mg, Ca, Na, K 3. Chapter 5 Self Teset - Subjecto.com It is viscous and hence traps gas, and explosively erupts due to pressure built by gases. Volcanoes are generally found where tectonic plates are diverging or converging. More broadly, fragmentation is a consequence of increasing stress and/or strain rate during magma ascent ( Dingwell, 1996 , Gonnermann and Manga, 2007 ). Andesitic magmas typically have high viscosity and thick flows, and are explosive. lava domes. Figure 11.9 Lava flows. Types of Magma: Basaltic lava flows easily because of its low viscosity and low gas content. It has the appearance of vesicular lava. As erupted magma blobs that partly congeal before falling to the ground. Andesitic magma has the same composition as andesite and fuels Mount St. Helens in Washington. This fragmentation condition is applicable to low-viscosity (crystal-poor) mafic magmas, where fragmentation is most likely to be controlled by inertia. E.g. Acidic lava , which is very viscous (sticky). Andesitic magma - SiO 2 55-65 wt%, intermediate. Left: A geologist collects a sample from a basaltic lava flow in Hawaii. Because of this flowability, erupted basalt can reach distances greater than 20 km. Magma with a high silica content has a high viscosity and flows quickly, high viscosity and flows slowly, low viscosity and flows quickly, low viscosity and flows slowly 2. What is the viscosity of basaltic magma? Term. ANDESITIC LAVA. Geologists identify the types of magma by their silica content which affects their gas content, temperature, and viscosity. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Andesitic magma erupts explosively since it tends to have high gas content. Magma (from Ancient Greek μάγμα (mágma) 'thick unguent') is the molten or semi-molten natural material from which all igneous rocks are formed. D) low viscosity and flows slowly. Explosive Eruptions. High viscosity and low dissolved gas content. Andesitic magma, which is lower in temperature, has more silica and a lot of dissolved gases and is more likely to explode when it reaches the surface. 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