VolcanoesVolcanoes are natural phenomena found on the Earth's surface through which molten rock and gas escape from underground (Tarbuck, 139). These volcanoes are very interesting to observe and study due to their astonishing phenomena and majestic lava eruptions. Volcanoes have been studied since the beginning of humanity and the word "volcano" is thought to derive from Vulcano, a volcanic island in the Aeolian Islands in Italy, whose name in turn derives from Vulcan, the name of a god of fire in Roman mythology. Made up of different types, volcanoes can extrude different forms of magma and can also release more gas. These extruded materials can affect the Earth's structure and atmosphere. There are three types of volcanoes on Earth. The most common type of volcano is a cinder cone. An ash volcano is built from ejected bits of lava that take on the appearance of ash as they begin to harden in flight. (Tarbuck, 152) The structure of this volcano is determined by the shape and slope that the pyroclastic material forms as it hardens. These volcanoes are usually symmetrical in shape, with elongated sides and may have large craters caused by volcanic activity (Tarbuck, 153). Examples of cinder cone volcanoes are Holocene in Utah and Capulin in New Mexico. In addition to the cinder cone volcano, the shield volcano is also another type of volcano common on Earth. The shield volcano is produced by the accumulation of fluid basaltic lava and has the shape of a large, slightly domed structure (Pillai). Younger shields tend to emit fluid lava from a central vent and have sides that vary from 1 to 5 degrees (Pillai). On the other hand, the older shield volcano......center of the map ......cause_and_effect_of_volcanoes_pg2.html?cat=58>.Pillai, Maya. “Volcanic Eruptions: What Causes Volcanoes to Erupt.” Buzzle Web Portal: Intelligent Life on the Web. Network. May 29, 2010. .Sigurdsson, Haraldur. Encyclopedia of volcanoes. San Diego: Academic, 2000. Print.Tarbuck, Edward J., Frederick K. Lutgens, and Dennis Tasa. "Volcanoes and other igneous activities". Introduction to Earth physical geology. 8th ed. Upper Saddle River, NJ: Pearson/Prentice Hall, 2005. 138-71. Print."Volcanic gases and their effects." USGS.com. U.S. Department of the Interior, April 30, 2010. Web. May 29, 2010. .Williams, Howel, Alexander R. Macbirney, and Christine Macbirney. Volcanology. San Francisco, California: Freeman, Cooper &, 1979. Print.