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Back to Subjects - Environmental Science

Volcanoes

Volcanoes Shannon Lindal Volcanoes are one of the most destructive yet fascinating geological land forms in our natural environment. They consist of a fissure in the earth’s crust above which a cone of volcanic material has accumulated. The cone is formed by the deposition of molten or solid matter that flows from the interior of the earth through an indented vent, called a crater, which is found at the top of the cone. In this report I will discuss different states of volcanic activity, different forms of volcanoes and their properties and Some volcanoes are more active than others. Some are even in a state of constant eruption an example of this is Izalco, located in El Salvador, it first erupted in 1770 and has been in a state of eruption ever since. In a belt that circles the Pacific Ocean their are many active and erupting volcanoes. For obvious reasons this area is referred to as the Ring of Fire. The activity of the volcanoes varies , for example, Vesuvius will continue in a state of moderate activity for long or short time periods and will then become stagnant or in-active for months. If an eruption succeeds prolonged dormancy it will usually be fairly violent, as was the eruption of Mount Saint Helens after 123 years of stillness. The potential danger of an active volcano can be seriously threatening to civilization for more reasons than just the initial eruption of molten rock, disasters, such as mud flows, triggered by an eruption are also serious hazards. Composite cones are formed from a combination of eruptions. First the volcano will have an explosive eruption that ejects huge amounts of steam, gas, and ash. This is followed by the ejection of lava. Most composite cones are built of layers of fragment materials and flows of lava, all inclined outward away from the vent. Both Etna, in Sicily, and Vesuvius, near Naples are examples of composite cones. The most common type of volcanic cones are stratovolcanoes. A large stratovolcano will be built with many layers of ash and lava. Mt. Saint Helens, Rainier, and Mt. Fuji are all examples of strata Shield volcanoes are made of thousands of thin lava flows. Because the flow of the lava is generally fast, it is able to travel far from the vent. The resulting volcanic land form has a broad base and gentle slopes. Shield volcanoes are the largest volcanoes. Some shield volcanoes, such as Mauna Loa, are amazingly huge at sea level Mauna Loa is 60 miles wide, is 30,000 feet from base to summit, and has a volume of roughly 40,000 In a composite eruption the lava is highly charged with steam and other gases, like carbon dioxide, hydrogen, carbon monoxide, and sulfur dioxide which continuously escape which escape from the lava’s surface with violent explosions and rise in a turbid cloud. This cloud discharges showers of rain. Large and small particles of lava are shot upward, forming a fountain like formation of drops and fragments, which are categorized as bombs, cinders, or ash depending on their size and shape. Lava rises in the vent and eventually spills out of the crater or squeezes, as a mass, out of a fissure on the side of the cone. This is when the crucial or destructive point of an eruption occurs. The volcano may return to a quiescent state after a final ejection of fragment material. For a period of time following the eruption of lava or fragment materials, the volcano will give off acid gases and vapor. After this, hot springs may form from the volcano. eventually volcanic heat will disappear, and cool water will issue from the volcano and the ground in it’s When a volcano becomes inactive it undergoes a reduction in size through erosion caused by flowing water, glaciers, wind, or waves. The volcano may become totally ruined leaving only a volcanic pipe filled with lava or fragments. The volcanic pipe extends from the earth’s surface to the lava reservoir. Bibliography:

Word Count: 674