what creates a volcanoes?
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A volcano is a geological landform usually generated by the eruption through a planet's surface of magma, molten rock welling up from the planet's interior. Other forms of volcano include ice volcanoes (particularly on some moons of Jupiter, Saturn and Neptune) and mud volcanoes. On Earth, volcanoes tend to occur near the boundaries of crustal plates. Important exceptions exist in hotspot volcanoes, which occur at locations far from plate boundaries; hotspot volcanoes are also found elsewhere in the solar system, especially on its rocky planets and moons.\n \nSmoking Bromo and Semeru (background) volcanoes on Java in Indonesia.\n\nMud volcanoes are formations often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano.\n\nThe name "volcano" is thought to derive from Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn originates from Vulcan, the name of a god of fire in Roman mythology. The study of volcanoes is called volcanology (sometimes spelled vulcanology).\nContents [hide]\n1 Volcano classification \n1.1 Erupted material\n1.2 Shape \n1.2.1 Shield volcanoes\n1.2.2 Cinder cones\n1.2.3 Stratovolcanoes\n1.2.4 Supervolcanoes\n1.2.5 Submarine volcanoes\n1.3 Subglacial volcanoes\n1.4 Classifying volcanic activity\n2 Notable volcanoes \n2.1 Volcanoes on Earth\n2.2 Volcanoes elsewhere in the solar system\n3 Volcanology \n3.1 Volcano formation \n3.1.1 Tectonic environments of volcanoes \n3.1.1.1 Constructive plate margins\n3.1.1.2 Destructive plate margins\n3.1.1.3 Hotspots\n4 Predicting volcanic eruptions \n4.1 Seismicity\n4.2 Gas emissions\n4.3 Ground deformation\n4.4 Iceberg tremors\n4.5 Hydrology\n4.6 Remote Sensing \n4.6.1 Local Predictions\n4.6.2 Early Warning for Lahars\n4.7 Predicting future eruptions of Mt. Etna\n4.8 Monitoring of Sakurajima, Japan\n5 Effects of volcanoes\n6 Past beliefs\n7 See also \n7.1 Lists\n7.2 Types\n7.3 Specific locations\n7.4 Volcano-related phenomena\n7.5 General topics\n7.6 People\n8 References\n9 Further reading\n10 External links\n\n[edit]\n\nVolcano classification\n[edit]\n\nErupted material\n\nOne way of classifying volcanoes is by the type of material erupted (ejecta), since this affects the shape of the volcano. If the erupted magma contains a high percentage (>65%) of silica, the lava is called felsic. Felsic lavas tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome. This type of volcano has a tendency to explode when erupting, because the viscous lava traps volatiles (gases), which cannot escape easily. Mount Pelée on the island of Martinique is another example. Pyroclastic flows (ignimbrite) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit.\n\nIf, on the other hand, the magma contains a relatively low percentage of silica, the lava is called mafic or basaltic and will be fluid as it erupts, capable of flowing for long distances. Mafic refers to the chemical composition of the lava—it contains higher percentages of magnesium (Mg) and iron (Fe), and correspondingly lower percentages of silica. Due to its low viscosity, v
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Curiously, I could not find a comprehensive listing.  This site might be helpful, however, or at least give you a start.\n\nhttp://dir.yahoo.com/Science/Earth_Sciences/Geology_and_Geophysics/Volcanology/Volcanoes
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You need to include:\n1. A world map of volcanoes. \n2. Statistics about volcanoes (average number of people died from them, how frequently they erupt and destroy things).\n3. Glossy color pictures of volcanoes.\n4. A scientific basis, such as \n.....a question "why do volcanoes occur?"\n.....specific hypotheses as explanations of natural phenomena (a short guess about why volcanoes erupt before the kid does any research, such as "I thought volcanoes erupted because it was like a big pimple. I wasn't sure, so I decided to research this topic.")\n.....research about why (check the Internet, encyclopedia or library)\n.....a conclusion "volcanoes happen because ..."\n.....and "my hypothesis was wrong. I found that volcanoes are not like pimples. They are more like open arteries, because once they erupt they keep spewing until they go dry."\n5. All the good volcano projects have videos of live volcanoes (use an LCD monitor).
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there is a hot core in the center of the earth, this escapes from fissures in the earths crust,finding its way up and out of the earth surface through fractures in the platelets. on these platelets the lava flows and when cooled becomes rock hard. when this happens in a volcano type of environment the pressure builds up over time, and the result is the "Blowing of the top/side" of the volcano, causing molten lava to flow, often causing damage to human, and plant life, that is around the base of the volcano..
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Basically one of three ways. These are extrusion, intrusion, and accretion. \n\nExtrusion is the process of volcanism. Volcanoes erupt molten rock that may have originated as subducted oceanic crust or deeper rock. This magma adds huge volumes of rock to the crust as it erupts and cools into solid rock. \n\nIntrusion is a similar process, but no eruption takes place. Large bodies of molten rock float upward over long time periods through the crust. When these cool and harden they are called plutons or batholiths (depending on size-batholiths are larger). These form large parts of the crust.\n\nAccretion is the other method. In some instances plate tectonics can force oceanic plates up and over continental plates. These often form what are called ophiolites where we can examine oceanic crust on dry land. Large parts of continents or islands are often forced against continental plates. This can force sediments and oceanic crust upward creating what are called 'accretionary terrane'. Much of California is an accretionary terrane, built of islands in a fore arc subduction zone that were forced up against a paleocoastline that once was near the eastern border of present day California. \n\nHere two other explanations similar to my own that illustrate these processes:\nhttp://www.physicalgeography.net/fundamentals/10j.html\nhttp://earth.leeds.ac.uk/assyntgeology/extra_info/ehistory.htm
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A destructive plate boundry causes one plate to be subducked below another, (sucked under basically) this causes it to melt and then rise to the surface where it forms the Mount Pelee volcano\n\nHope that helps
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In a phrase, volcanic rock.\n\nEach volcano erupts constructively and destructively, and some of those constructive eruptions build the sides of the volcano.  The type of magma determines the color and shape.
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volcanoes are built when tectonic plates push together, the way mountains are formed. except volcanoes have magma inside of them. the gas and magma inside are under extreme pressure, and this pressure pushes its way through small cracks in the rock, eventually escaping in an eruption of gas that brings lava with it. a lot of people have been killed by eruptions, but i cant tell you how many. the lava takes weeks or months to cool down unless it hit the water, which will cool it in a matter of days.
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Not exactly pressure.  Tectonic plates under the Earth's crust are constantly in motion.  When they collide, mountains are formed.  These mountains become volcanoes when the tectonic plates hit each other and then move further apart, therefore creating a direct channel to the molten core of the earth.  When the molten material builds up it shoots up the hole of a volcano.
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Several things happen when a volcano is about to erupt, some of the most obvious are: \n\n1.The number and size of earthquakes increase in and around the volcano. \n\n2.The ground deforms or "bulges" at the eruption site. \n\n3.A lot more gas comes out of the volcano.
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Mt. St. Helens was formed from the subduction of the Juan de Fuca Plate underneath the North American Plate.  Subsequent eruptions, producing basalt and andesitic lava flows, have either reshaped or built up the volcano over time.
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volcanic crater - a bowl-shaped opening at the top of a volcano, its that opening from which lava, gases, and ejecta ..\n\nfrom the wikipedia : Perhaps the most conspicuous part of a volcano is the crater, a basin of a roughly circular form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of vast depth. Very large features of this sort are termed calderas. Some volcanoes consist of a crater alone, with scarcely any mountain at all; but in the majority of cases the crater is situated on top of a mountain (the volcano), which can tower to an enormous height. Volcanoes that terminate in a principal crater are usually of a conical form.\n\nOn Earth, volcanic explosion craters are often formed when magma rises through water-saturated rocks and causes a phreatic, or steam explosion. Volcanic explosion craters from phreatic eruption often occur on plains away from other obvious volcanoes. Other volcanic eruptions can cause mild explosions, often in a series of events. Some volcanic craters form by collapse with little or no explosive activity. Volcanic craters are typically seen either on the summits or on the flanks of volcanoes. Volcanic craters have also been identified on the Moon, Mars, Venus, and Io.
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4. D\nThe most explosive volcanoes are those containing a lot of silica.  The shape of the silca molecule is a bit like a pyramid which means that cannot move past each other very easily.  This makes them very viscous and so it takes much more energy to get it to move and the energy comes out in a single event.\n\n12. B\nIt's the difference between min and max.
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Mt. St. Helens is a subduction volcano.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the oceanic plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!
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Shield volcanoes are composed of basaltic, low viscosity lavas. which have low height/area aspect ratio (think about Hawaii).\nComposite volcanoes have a high height/are aspect ratio and are formed formed by andesitic to dacitic lavas, and pyroclasts. They are also called strato-volcanoes.\nThe domes, are dome shaped eruptions, lavas or volcanoes formed by dacitic to rhyolitic lavas, with some pyroclasts in the rims. They can also form cake like shapes or even very impressive protruding spine-shaped extrusion of very viscous magma.
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It depends on the volcano.\n\nIf magma - molten rock - is erupted it forms new formations when it cools. On the big island of Hawaii, the volcanic eruptions have added a lot of new land to the island.\n\nIf it is a pyroclastic flow - fast, hot gasses and volcanic debris -  like the one that destroyed Pompeii or Mt. St. Helens, there may not be any new land created and the existing land will be radically altered.\n\nIn general, when a land based volcano erupts, the lava and stone and ash build up around the eruption site into a cone shape.\n\nUndersea volcanos spweing lava also build up, but not in a cone shape. Once the hot rock hits water it starts to cool into large pillow-shaped forms.
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I was taught in school that it is due to radioactive decay of elements in the core.  That is pure bullcrap.  If it were true, every time a volcano exploded, there would be radioactive toxins spread out across the world.  Others say gravity pushing on the substances create heat and liquification of earth.  This may be somewhat true.  If you put a piece of solid ice in a chamber and put extreme pressure on it, it turns to liquid.  There must be some other source of internal heat generation though.  I have never found a satisfactory answer to date.  I really don't think anyone knows, just like gravity is still a big mystery.