why do volcanos erupt.?
543189
High pressure builds up inside the magma chamber due to gases & the actual heat inside.\n\nComposite volcanoes usually are the worst for explosive eruptions b/c of the amount of trapped gases that build up. They erupt lava that is high in silica which also makes it thick. This combination usually leads to deadly pyroclastic flows.
833629
1.  Being near active volcanos probably means you're also in an area that is subject to earthquakes, for the same reason (plate tectonics).\n\n2.  If they erupt, they can do so explosively, in which case hot ash and smoke can suffocate you and burn you to death.  Or they can erupt slowly, like the ones on Hawaii typically due, in which case the lava can overrun homes, properties, etc.\n\n3. Volcanic ash that settles out of the atmosphere can damage respiratory health.\n\n4.  The lava and hot ash can rapidly melt any snow or ice that may be on the mountain, causing devastating floods and mud flows (lahars).\n\n5.  Volcanic dust can be hazardous to airplanes.\n\n6.  If the eruption is big enough, the ash can cause temporary cooling of the earth's climate by blocking sunlight.
1016696
Volcanoes are the result of the dynamic of Earth.\nEarth's crust is broken in many blocks (tectonic plates) that are in motion respect one another. Mostly of volcanoes are located along boundaries of adjacent plates.\nVolcanic eruptions near tectonic plates' boundaries are driven by the magma that ascend from deeply beneath the crust\n\nScientific predict volcanic eruptions by studying some geophysical and geochemical parameters:\n * increasing of the seismic activity near the volcano\n * changes in the quantity of gases (CO2, SO2, etc) expelled by the volcano\n * observed changes in magnetic or geoelectrical explorations: studying the surface of the volcano with magnetic geoelectrical methods.\n\nYou can read more at links below
54493
Volcanoes are usually situated either at the boundaries between tectonic plates or over geology hotspots. Volcanoes may be either dormant (having no activity) or active (near constant expulsion and occasional eruptions), and change state unpredictably.\n\nSurprisingly, there is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of activity. Given the long lifespan of such volcanoes, they are very active. By our lifespans, however, they are not. Complicating the definition are volcanoes that become restless but do not actually erupt. Are these volcanoes active?
192697
It is directly related only to earthquakes.  When a plate boundary ruptures, an earthquake occurs.\n\nIt is indrectly related to volcanism.  Most volcanoes are located on plate boundaries.
924357
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.
612872
There are three classifications for volcanoes in respect to their activity. Two of those are inactive.\n\nActive volcanoes have erupted recently or are expected to erupt in the near future. They are showing signs that they are active such as releasing gases, uplift of surrounding land, movement of magma, & mini earthquakes.\n\nDormant volcanoes are those that have erupted at least once during recorded human history but have not erupted since that time. They are expected to erupt at some point in time but are not currently showing signs.\n\nExtinct volcanoes are ones that have not erupted in recorded human history but evidence left behind tells us that it had erupted at one time. These volcanoes are considered to be dead and will not erupt again.\n\nSo to answer your question directly, the only volcanoes that are active are the ones that are not extinct or dormant.
998878
Both are held under pressure. The molten rock (lava) is full of gases like a fizzy drink and when the pressure is released the gases escape causing an explosive reaction.  IE. the volcano erupts and the drink fizzes up when the gas is released at normal atmospheric pressure.
871602
The last time I read anything about volcanos on Earth's Moon they were the result of internal melting caused by meteor strikes. Dispite the apparent smallness of the Moon as seen from Earth it is a very large object and has been refered to as Earth's "dead" twin.  \nFor a Volcano to affect the orbit of any object, moon or planet, it would have to be very big.  The largest known volcano in our solor system is Olympus Mons on Mars.  It has apparently erupted with enough violence in the past to eject rock into space. At least that is the theory proposed by those who believe they have found pieses of Martian Ejecta on the South Pole of Earth. That didn't do anything to the orbit of Mars. Moons and planets have so much mass that jogging them from their orbits would take more energy than even a Volcano could muster I think.\n\nAs for how the eruptions would behave with no atmosphere, there would be no wind to blow the ejecta away from the point of origin so the ejected particals would just continue on in thier original trajectory until the gravity of the moon in question was able to pull them back down. I'd guess that this would make the 'cone' of the volcano be fairly even. The gases from the eruption that were not trapped inside the more quickly cooled molten rock would escape into space.\n\nSorry about any mis-spelling. I couldn't get the spell check to work.
245729
the vibrations from the earthquake shkae the earth's plates making the volcano's magma more active and makes it easier for it to break through rock sicne its weakened by the earthwuake, but most times it's the volcano that causes the earthwuake not the other way around
845867
Eruptions have many effects, both good and bad. A major eruption will blow rock, gases and ash into the air. Sometimes melted glacial water mixed with falling debris can cause mudflows in rivers and streams that are capable of sweeping away entire towns. In the short term (the time that the eruption occurs), this can be devastating. Indeed, many living organisms can die, including humans, plants, animals etc., and there can be some economical damage, including destruction of towns or villages, crops, water supplies and food resources. However, in a long period of time, through the force of erosion, volcanic material (particularly ash) will break down. This can form a very rich kind of soil, good for plant growth. Farmers in places near volcanoes can grow an incredible stockpile of good, fresh food because of the good soil.\nLava eruptions are far less dangerous than explosive ones (but lava flows can still pose as a threat). Though a lava flow is very hot and capable of burning anything in its path, it does not move very fast. These lava flows can vary in size, however, and sometimes a flow may destroy some plant life, as well as human settlements. Villages in Hawaii have been burried by lava flows, and there are articles in newspapers that show pictures of houses burning, or abandoned houses half-buried in cooled lava. But, like the explosive eruptions, when lava cools and breaks down over time, it too can form rich soils.\nAsh, an aspect mentioned before, is a volcano's legacy. The ash from a major eruption can travel around the globe in a matter of days. Ash, when seen under a microscope, consists of tiny, sharp particles. These particles can be extremely harmful to the human lungs, or the lungs of any other animal, for that matter. How would you feel if your throat and insides were scratched by miniature, sharp rocks? Ash can also be the opposite of a good soil maker for farmers. If too much ash covers a field, the field is ruined, for the plants will suffocate in the layers of debris. Sometimes, like it was with Mt. St. Helens, ash can pile up on top of roofs of houses, and any roof can cave in from the weight of it (just like snow). \nSo really, volcanoes make up a huge part of Earth in general, and they can have mixed effects on the environment.
91291
The short answer is plate tectonics. Volcanoes can be divided into three major groups, those that are connected to a spreading center, like the mid-ocean ridges, those connected to a subduction zone, like Mt.St. Helens, or much of the Indonesian archipelago, and intraplate volcanism like Yellowstone. \n\nWhere the lithosphere (or crust) overlies an area within the asthenosphere (the layer of the earth under the crust) there are currents rising that cause volcanoes to form. These areas are called spreading centers. At the edges of the oceanic plates the plates often are forced under continental or even other oceanic plates. Where these plates are being forced downward, called subduction, there are volcanoes formed by melting magma rising from the descending plate. Most of the volcanoes around the edges of the Pacific Ocean are of this type, and are the reason it is called the "ring of fire".\n\nThe other group of volcanoes are related to what are called hot spots. These are places under the crust where the asthenosphere is especially hot. Yellowstone, and the Hawaiian Islands are examples of this. The hot spot under Hawaii is stationary, and as the Pacific plate has moved across it, it has produced a long chain of volcanic islands. \n\nYou can explore what makes volcanoes work at the following website sponsored by NASA:\nhttp://www.geology.sdsu.edu/how_volcanoes_work/Home.html
585860
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..
858300
A volcano possesses explosive power plus a flow of volcanic lava that tends to follow i hope that helps. It combines both power and flow but a different kind to that of water.
810078
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.
158817
Several ways. This also depends on the type of eruption. Often earthquakes occur before, or during an eruption causing things to topple. Also, often the size of the volcano itself changes. Lava cools to rock after flowing over the landscape, and kills the organic material it comes into contact with. The gas released during an eruption is also deadly! If it is an eruption like Mt. St. Helens was, the land is covered in ash and decimated by mudslides.
197975
The guide was right. It does break the surface tension. It's the surface tension that delays the eruption time. Otherwise, it would erupt almost exactly the same time everytime.