Kilauea volcano HAWAII, August 2010
volcanism and VOLCANOES
Given the recent and impressive emissions from Chilean volcanoes in southern tip of South America , which certainly attracted much attention and concern of those who live in this area the world , we consider it appropriate and necessary to raise some explanatory comments about these seizures of nature.
Among the phenomena of internal origin, capable of changing the earth's surface is the volcanic activity . Scientifically, the term volcanic phenomena all those linked with the process of rising magma , ie the igneous fluid matter contained within the crust . The volcanoes, in addition to its opulent beauty and majesty that print, offer much geomorphological interest and great value from an economic standpoint.
The man fears them, intended to predict eruptions, but also a growing recognition that they are a source of fertile soil and wealth.
Indeed, although volcanic eruptions can mean destruction, are also valuable sources of energy , fertile soil, useful materials, elements increasingly heavily exploited.
The volcanoes igneous forms are external. Usually it is a mountain that occasionally throws lava, fire, smoke and fumes, through an opening called crater.
But they can be much more than that. The volcano is primarily a communication, a crack, hole, where igneous materials inside are driven to the surface.
According to the way it performs magma emission, may have several aspects: (1) cone volcanoes, which are central issue, and moreover (2) Volcanoes cracks and mantles, cracks emission.
The cone volcano is the most common. Presents a volcanic cone , which usually has its summit crater, like a funnel that is continued by a fireplace , which occupies almost always the cone axis. As for the fireplace ascieden igneous materials, it is called cone volcano central rate.
The fireplace, to a certain depth, can be divided and communicate with the outside through lateral craters without terminal disappears, or obstruction of it. A clear example of this type is the Etna in Sicily, characterized by the large number of secondary craters as curious.
Some volcanoes have enormous cavities nearly circular, steep walls to the interior, called Caldeiras , name typically given in the Azores Islands . In reality, these cavities are not properly craters in relation to the fireplace, but more profound and extensive depressions whose precise origin is still disputed today. Appear to obey subsidence, as the case of volcanoes and Krakatoa Crater Lake .
cone volcanoes have been formed and are formed by accumulation of eruptive materials around the outlet, issued in successive eruptions.
Notable examples of cones arising in the near future are in Mexican territory , such as Jorullo in 1759, and closer in time the ParicutÃn . The latter just born in 1943 and quieted in 1952. His short life was very useful to science, as was a laboratory, where the man was born and grew learned how a volcanic cone, which initially rose about 50 meters per day.
The appearance and characteristics of cones and craters, certainly depends on the materials present and the forms of volcanic eruption.
cones can be erected with an indentation terminal, as the Nicaraguan Momotombo , or low and high base, with a huge crater such as Hawaii .
can be formed by ash or lava exclusively, or alternating layers of one and other materials in the form of strata, which is a typical example Vesuvius.
The volcanoes or volcanic fissure cracks made their broadcasts by cracks or fissures, which may be minor cones. Are rare, but there are examples, such as Iceland typical (the famous Laki Rift 35 kilometers) in Hawaii the majestic Mauna Loa , and New Zealand the curious Tarawera volcano. In the above cases, it is typical that its many craters act simultaneously.
The mantle volcanoes are also caused by cracks. They differ from above by the extension of cracks, open in times of great dislocations of the crust, and issued by the huge amounts of lava , reaching to cover considerable areas on different continents.
continue with more insights and comments on these topics in future deliveries.
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