Volcanos
Volcanoes Volcanoes I. Introduction. II. Volcano's formation. III. Volcanic materials. A. Lava B. Tephra C. gases IV. Eruptions A. Explosive Eruptions B. quiet Eruptions V. types of volcanoes A. shield volcanoes B. cinder volcanoes C. composite volcanoes I. Introduction. A Volcano is an opening in the earth's crust through which lava, ash, and gases are ejected. Most volcanoes have steep sides, but some can also be gently sloping mountains or even flat tablelands, plateaus, or plains. The volcanoes above sea level are the most popular, but the majority of the world's volcanoes lie beneath the sea, formed along the global oceanic ridge systems in the deep ocean floor. According to the Smithsonian Institution, 1511 above-sea volcanoes have been active during the past 10,000 years, 539 of them erupting one or more times. An average of 50 to 60 above-sea volcanoes worldwide are active in any given year; about half of these are continuations of erupt
Composite volcanoes are made up of layers lava that previously erupted. Composite cones are mostly formed by andesite lava. Composite volcanoes make up more than 75% of all volcanos. Composite volcanoes erupt for hundreds and thousands of years. Composite volcanoes erupt explosibly and are often found chains with other volcanoes; one of this is the ring of fire. Amount of silicon dioxide B. Tephra. Tephra are the rocks formed by magma that erupts. Well known tephra include pumice, cinders and volcanic ash. Volcanic ash refers to the rock particles that are smaller than 2 mm and erupted from a volcano. Volcanic dust is about .06 mm, volcanic blocks are about 65mm, and it's the biggest object that can erupt from volcanoes. C. Gases. Gases are released from volcanoes during an eruption. All eruptions release gas. Gas is the main reason of an eruption been explosive or quiet. The gas comes from the hot magma or lava touching water during the eruption. The color of the gas depends whether the gas was mixed with tephra. Volcanic gas is mostly made up of steam, carbon dioxide and sulfur dioxide. IV. Eruptions The eruption of a volcano depends on the composition of the magma below it, the gas in the magma and what type of volcano it erupts from. The stiffer the lava, the more explosive the eruption will be. Throughout explosive eruptions, the lava erupted is frayed into shreds, forming a variety of fragmental materials depending on the state of the lava and on the force of the explosions. Explosive eruptions can release a large amount of material into the ai
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