There are several main types of volcanic structures. Linear volcanoes or volcanoes fracture type have extended feeders associated with a deep split in the bark. Typically, the liquid magma basalt flows from these fissures and spreading to the sides, forming large lava. Along the cracks appear shallow shafts spray broad, flat cones, lava fields. Volcanoes of the central type have a central supply canal or orifice, leading to the surface of the magma chamber. Muzzle ends with the extension, the crater, which is the growth of volcanic structure moves up. Thyroid volcanoes are formed as a result of repeated emissions of liquid lava. This form is characteristic of volcanoes spewing basaltic lava of low viscosity: it follows both from the central crater and from the slopes of the volcano. Lava evenly spread out for miles. The survey of such volcanoes is fairly common. The next type of volcanoes emit from their mouths just are not dense matter, like rocks and ashes: the largest debris accumulated layers around the crater. So, every eruption of the volcano becomes higher. After the eruption, when the activity of the volcano or stops forever or it sleeps for a thousand years, at the volcano and its surroundings remain the processes associated with the cooling of the magma chamber and called post-volcanic. Volcanoes are not only on Earth but also on other planets and their satellites. The highest mountain in the solar system is a Martian volcano Olympus, whose height is estimated to several tens of kilometers. The main areas of volcanic activity is South America, Central America, Java, Melanesia, the Japanese islands, the Kuril Islands, north-western U.S., Alaska, Hawaiian Islands, Aleutian Islands, Iceland, Atlantic Ocean. One of the unsolved problems manifestations of volcanic activity is to determine the source of heat for local melting of the basaltic layer or mantle. So many surveys are done in this area. Some geologists believe that the melting is due to local high concentrations of radioactive elements, but the concentrations appear to be unlikely in nature, while others suggest that the tectonic disturbances in the form of shifts and breaks are accompanied by release of thermal energy. There is another point of view that the upper mantle at high pressures in the solid state and when the pressure drops due to cracking, it melts and the cracks are an outpouring of fluid lava.
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