Volcanoes are considered unique natural phenomena which drew the attention of the human foot since they play a great role in the geological processes that affect the history of the evolution of the earth's crust and posed . This is because most of the affected parts of the earth's crust and underwent operations impulsivity in formation processes contribute to impulsivity . According to the study of volcanoes in identifying centers of earthquakes and volcanoes study branch of geology, which became known as freestanding Volcanology Volcanology. Volcanoes and associated metals and ores are very important in economic terms.
The definition of the volcano :
The volcano is that place , who graduated or material emits Alziria warm with vapors and gases accompanying her on the depth of the earth's crust and it happens through nozzles or cracks . And accumulate magma flow or by type of form which forms the floor of different conical hills or high volcanic mountains .
Parts of volcanoes :
If you look at the form you'll find that it consists of:
1 - Mount conical :
Composed of rocky debris or hardened lava . Speak to a material that crater of the volcano and were all or some of them in the molten state .
2 - nozzle : It is a rounder cavity shape almost at the top of the cone , the wider the range from a few thousand meters . And emerges from the nozzle at intervals and gas blocks of rock and mortar and lava and molten materials ( Lava ) may have more of a volcano crater to the secondary side of the main crater at the top as you can see in the figure :
3 - chimney or rod : a channel extending from the bottom of the crater to the bottom of the oven where the related magma underground . And hurtling through volcanic material to the nozzle . And sometimes known as the volcano neck .
In addition to the main chimney , it may be several stacks of volcano -related secondary craters .
Types of volcanic material :
Comes out of volcanoes , while revolutions rocky debris solid and liquid materials .
1 - rock debris :
Emerges as a result of volcanic eruptions rocky debris solid various types and sizes, usually in the first period of volcanic eruptions . And rock debris derived from the rigid crust extracted from the walls of the neck as a result of payment of lava and gaseous substances emanating from the magma strongly , violence and rock debris consists of materials in different sizes , including rock masses , shells and pebbles , sand and volcanic dust .
2 - GAS:
He graduated from volcanic activity during the gas water vapor , which stems great quantities of a component of the huge clouds mixed with dust and other gases . And condense the vapors , causing the heavy rain falling in the vicinity of the volcano . Accompanied by explosions and rainfall occurs, lights , electric friction granules arise from volcanic ash each other and as a result of weather disturbances , and except for the severe heat of water vapor , volcano spews gas multi notably hydrogen , chlorine , sulfur, nitrogen , carbon and oxygen.
3 - lava :
Blocks are liquid volcanoes disgorged , and has a temperature of between 1000 m and 1200 m . And lava emerge from the crater , as bursting through the cracks and fractures in the aspects of the volcanic cone , those fractures created by the explosions and the pressure of magma blocks , and stop nature of the lava , and their appearance on the chemical composition of the magma blocks which emits two types namely :
A - Lava light pastel color :
This is characterized by bone viscosity , and thus slow the flow and like lava that emanated from the volcano Billy ( in the Islands Almrtnik in the Caribbean ) in 1902 was a dense sticky so it did not overwhelmed the move and took to accumulate and rise composed tower above the crater reached a height of about 300 m , and soon after that crash and break as a result of explosions caused by the release of gas .
B - Lava heavy dark :
They Lava basaltic , and the advantage of being liquid and moving to a large degree , the flow in the form of streams on the slopes of the volcano , and when it emerges lava through the fractions of great extension , it spread over large areas made up of plateaus spacious , and like the Ethiopian highlands and the Deccan Plateau , India and the Golan Columbia in North America .
Forms volcanoes :
1 - volcanoes, rock debris :
Varies depending on the shape of the cone material that consists of them. If the cone is made up entirely of rock debris , we found high steep for the space occupied by the base. Here we find the degree of slope of 30 degrees was sometimes up to 40 ° C and these forms usually arise as a result of volcanic eruptions . The islands in Indonesia .
2 - volcanic plateau :
Arise as a result of out lava and clumping around the main nozzle and the low-rise look for the space occupied by the large bases. And looks peaks like Bhiab convex Thdba Hina hence renamed volcanoes Plateau has originated cones of flow Mushorat lava intense heat and great liquidity, which has spread over large areas and is this volcanic plateau best representation in the volcanoes of the Hawaiian Islands volcano Mauna Loa , which has a height of 4100 m , which seems more like a spacious dome descend steeper easy Hina .
3 - volcanic stratigraphy :
Volcanic stratigraphy common type of existence , which is in the shape of former central modes and is composed of materials Mkhrotadtha rock debris and lava flows directed by the volcano eruption while restless .
And Alloafez be coming out of the volcano during eruptions in a row layers on each other , and some of them consisting of coarse material and another section of the materials minutes , and between this and that interfere lava in the form of a few bars of fish . It is this type arises from the stratigraphy in the installation and Cone This figure represents the Mayon volcano more active volcanoes in the Philippines nowadays .
The geographical distribution of volcanoes :
Volcanoes are spread over long ranges on the surface of the earth shown :
1 - range that surrounds the coasts of the Pacific Ocean , which is sometimes known as Ring of Fire , it runs on the eastern shores of the ocean above the heights of the Andes to Central America and Mexico , and above the heights of western North America to the Aleutian Islands and then on to the coast of East Asia to the islands of Japan and the Philippines and then to Islands of Indonesia and New Zealand .
2 - There is a lot of volcanoes in the Pacific Ocean and some of the same great grew up in a huge hall and appeared towering above the water level . Volcanoes , including the Hawaiian Islands , which is based bases in the ocean at a depth of about 5,000 m , and rises above the surface of the water more than 4,000 m , bringing the total height from the bottom of the ocean to the peaks of about 9000 m
3 - Southern Europe, the Mediterranean and its adjacent islands . The most famous active volcanoes here Vesuvius near Naples, Italy , and the islands of Sicily and Aetna Astro Mboli ( beacon Mediterranean ) in the Lipari Islands .
4 - Heights West Asia and months Ararat volcanoes and Alauzenz .
5 - ranging from eastern Africa and months Brkinh Kilimanjaro .
The effects of volcanoes :
1 - in the formation of Earth's surface :
We can thus advances to discern the effects of volcanoes in the formation of the Earth's surface they arise majestic mountains and plateaus spacious . When subsided arise in the cavities of their pores in those lakes rainforest.
2 - in human activity :
Strange that no human habitation near volcanoes play in order to be safe from dangers , as we find lived near them, but also on the slopes . Fberkan Vesuvius is surrounded by villages and towns, and is covered by gardens and fruit orchards and vineyards spread over all its aspects even near the top. The Agriculture also on the slopes of a volcano ( twelve ) on the island of Sicily to a height of 1200 m in the fertile soil is composed of black basalt that flow over the region during historical times .
These volcanoes unforgiving as arise from time to time , destroying a village or another can rest along the main road up the lower slopes of the volcano and twelve at the end of a flowing lava flows eternal evidence to indicate permanent danger posed to the region.
The famous island of Java Berakinh rebellious active volcanoes superiority in virtually every volcanoes of the world in the amount of spills and Alloafez that flowed from them since 1500 AD , however , we find the island full of the population , they are the thickest points of world agricultural population for the area is inhabited by about 75 million people because as we have said to fertility volcanic soil , has been established by the interest of the volcanoes function predict volcanic eruptions and warn the population before the volcanic eruptions, which reduces the risk of falling .