Types of Magma

57b8db992b59cd9940413962be29f6bf

09-11-17-2152

shutterstock_251331703-850x500

Magma is the hot fluid or semifluid material below or within the earth's crust from which lava and other igneous rock is formed by cooling. Magma is a mixture of molten or semi-molten rock, volatiles and solids[1] that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals, dissolved gas and sometimes gas bubbles. Magma often collects in magma chambers that may feed a volcano or solidify underground to form an intrusion. Magma is capable of intruding into adjacent rocks (forming igneous dikes and sills), extrusion onto the surface as lava, and explosive ejection as tephra, or fragmented rock, to form pyroclastic rock. Many people often uses the term "lava" for the red-viscous liquid that a volcano erupts, actually that is wrong, the right term is "magma." Three General Types of Magma

Basaltic Magma is made up of 45 to 55 percent silica. It is high in iron, magnesium and calcium and is low in potassium and sodium. The temperature of basaltic magma is around 1,000 to 1,200 degrees Celsius, based on laboratory measurement and limited field operations. Scientists find it difficult to determine an exact temperature because it is dangerous to get close enough to magma to measure it. Basaltic magma is the most fluid of the three types of magma, though it is still 10,000 to 100,000 times less fluid than water. It also has the lowest amount of gas of the three types. Basalt magma is found at Earth's "hot spots," such as Hawaii. When it cools, basaltic magma becomes basalt rock.

Andesitic Magma is the "middle" magma in terms of heat; fluidity, or speed of flow; and gas content. It is probably 800 to 1,000 degrees Celsius. It is made up of 55 to 65 percent silica with average amounts of iron, magnesium, calcium, potassium and sodium. When cooled, andesitic magma becomes andesite rock. Andesitic magma is somewhat explosive, coming to the crust of the Earth at reverse fault areas. In these spots, two plates in the Earth's crust move against each other in opposite directions, and the top piece moves up toward the surface rather than toward the planet's center. Small- to medium-sized earthquakes also release andesitic magma. An example of andesitic magma is the eruption of Mount St. Helens in Oregon.

Rhyolitic Magma is a type of magma formed by differentiation from basaltic magma in combination with assimilation of siliceous material, orby melting of portions of the earth's sialic layer.

Many rhyolites form from granitic magma that has partially cooled in the subsurface. When these magmas erupt, a rock with two grain sizes can form. The large crystals that formed beneath the surface are called phenocrysts, and the small crystals formed at the surface are called groundmass. Other Types of Magma

Ultramafic Magma - Today, our planet is too cool for ultramafic, or komatiite, magma to form. This is probably a good thing, since ultramafic magma would be the hottest and fastest-flowing of the magmas, running almost as fast as water down a volcano. In the distant past, ultramafic lava could reach as high as 1,600 degrees Celsius. Now lava rarely reaches above 1,200 degrees.

Felsic Magma, including ryolitic and dacite magmas, which are very thick and slow-moving. Felsic magma seems to form when the Earth's crust melts with seawater. It is highly explosive when erupting from volcanoes. Felsic magma is made up of 65 to 75 percent silica. It is low in iron, magnesium and calcium and is high in potassium and sodium. Compared to other types of magma, felsic magma is cool, reaching 650 to 800 degrees Celsius, and is high in volatile, or unstable, gases and melted rocks. Felsic magma forms huge calderas, like the Yellowstone caldera. When cooled, it forms ryolite or granite rock. How Magma Forms in the Earth?

As we have seen the only part of the earth that is liquid is the outer core. But the core is not likely to be the source of magma because it does not have the right chemical composition. The outer core is mostly Iron, but magma are silicate liquids. Thus, magma DO NOT COME FROM THE MOLTEN OUTER CORE OF THE EARTH. Since the rest of the earth is solid, in order for magma to form, some part of the earth must get hot enough to melt the rocks present. We know that temperature increases with depth in the earth along the geothermal gradient. The earth is hot inside due to heat left over from the original accretion process, due to heat released by sinking of materials to form the core, and due to heat released by the decay of radioactive elements in the earth. Under normal conditions, the geothermal gradient is not high enough to melt rocks, and thus with the exception of the outer core, most of the Earth is solid. Thus, magma form only under special circumstances, and thus, volcanoes are only found on the Earth's surface in areas above where these special circumstances occur. (Volcanoes don't just occur anywhere, as we shall soon see). To understand this we must first look at how rocks and mineral melt. To understand this we must first look at how minerals and rocks melt. Gases in Magma At depth in the Earth nearly all magma contain gas dissolved in the liquid, but the gas forms a separate vapor phase when pressure is decreased as magma rises toward the surface of the Earth. This is similar to carbonated beverages which are bottled at high pressure. The high pressure keeps the gas in solution in the liquid, but when pressure is decreased, like when you open the can or bottle, the gas comes out of solution and forms a separate gas phase that you see as bubbles. Gas gives magma their explosive character, because volume of gas expands as pressure is reduced. The composition of the gases in magma are: Mostly H2O (water vapor) & some CO2 (carbon dioxide) Minor amounts of Sulfur, Chlorine, and Fluorine gases The amount of gas in a magma is also related to the chemical composition of the magma. Rhyolitic magma usually have higher gas contents than basaltic magma. References: https://healthyliving.azcentral.com/different-types-of-magma-12406616.html http://study.com/academy/lesson/basaltic-lava-definition-characteristics.html https://www.britannica.com/science/andesitic-magma http://irtg-strategy.de/en/wp4/index.html https://lavamagmainfo.weebly.com/magma--lava.html https://www.emaze.com/@AOQTIQZQ/Andrew%27s-Volcano-video https://en.wikipedia.org/wiki/Magma https://www.google.com.ph/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwiq947But7XAhWLWLwKHahpBOEQFggsMAI&url=http%3A%2F%2Fwww.tulane.edu%2F~sanelson%2Fgeol204%2Fvolcan%26magma.htm&usg=AOvVaw1gnl2D4tte6KVKuDoEA4D4