Volcanoes - geological formations on the surface of the earth's crust or another planet's crust where magma reaches the surface, forming lava, volcanic gases, rocks, volcanic bombs and pyroclastic flows.
Volcanoes are divided according to the degree of volcanic activity on the active, dormant and extinct. An active volcano is considered to be a volcano erupted in historical time period or during the holocene. The concept of "active" is quite inaccurate, since the volcano, which has active fumaroles, some scientists refer to the active, and some refer this volcanoes to be extinct. Sleepers are considered to be inactive volcanoes, where there is still a possibility of eruptions, and extinct volcanoes are that on which eruptions are very unlikely.
However, among volcanologists there is no consensus as to define an active volcano. Period of volcanic activity may last from several months to several million years. Many volcanoes showed volcanic activity tens of thousands of years ago, but currently not considered to be valid.
Astrophysics, in the historical aspect, believe that volcanic activity caused, in turn, the tidal influence of other celestial bodies, may contribute to the emergence of life. In particular, it is volcanoes contributed to the formation of the earth's atmosphere and hydrosphere, throwing a significant amount of carbon dioxide and water vapor. Scientists also say that too active volcanism, such as on Jupiter can make the surface of the planet uninhabitable. At the same time, weak tectonic activity leads to the disappearance of carbon dioxide and sterilizing the planet. These two cases represent potential habitability of planets and boundaries exist alongside the traditional parameters of life zones for systems of low-mass main sequence stars.
There are more than 1,500 potentially active volcanoes all over the world. Many people somehow think that there are up to dozen of active volcanoes. In fact, their number reaches a thousand. This number includes both conventional and underwater volcanoes, the number of which can be much more bigger but they are not easy to find.(Rosi 15)
However, potentially active - does not mean that the volcano erupts at the moment or will erupt in the nearest future. No, it means that a volcano could erupt at any time, and now a volcano is just asleep. But there are 65 active volcanoes, and most of them are in Alaska and in Hawaii.
Scientists suggest that volcanic eruptions affect the climate. For example, they can cause long-term cooling. Volcanic gases are dangerous, the same sulfur dioxide combines with rain water, it forms sulfuric acid. Also, these geological formations emit large amounts of carbon dioxide and dust.
The most large volcanoes are called super-volcanoes. Their eruptions can lead to disastrous consequences: a rain of fire on thousands of miles from the volcano, global climate change because of the falling ash into the atmosphere. Usually such eruptions of volcanoes occur several times in 100,000 years. One is located in Yellowstone National Park, and scientists say that it may be ready for the next eruption.
The largest eruption occurred on the Indonesian island of Sumbawa it was a volcano Tambora. During the eruption killed 100,000 people. It is believed that Indonesia is the largest number of historically active volcanoes - 76.
Though in the world there are thousands of volcanoes, only about 500 of them are active at the moment. And at the moment, about 500 million people live in close proximity to active volcanoes.
Works cited
Rosi, Mauro. Volcanoes. Toronto: Firefly Books, 2003. Print.
