Volcanoes in Africa
Characteristics of a volcano
|Automatic translation||Updated April 20, 2013|
A volcanodefinition of volcanism, given by an American geologist: "It's all physical and chemical phenomena that accompany the ascent of magma." is composed of three parts: a reservoir of magma in depth, one or more chimneys volcanic communicate with Inside the Earth, and the volcanic mountain which is a Crater, a crater cone, a dome, a lava flow or a deposit product explosion (slicks sanded, etc.).. The Volcanic eruptions give birth to popular beliefs which mixed superstitious terrors and fantastic legends. It is true that some eruptions can be devastating to point to Disappearance of civilizations. A volcano is a relief of the crust terrestrial (submarine or air) formed by the ejection and stacking Material from the rise of magma in the form of lava and tephra The Téphras represent all materials (solids and liquids, caused by gas) emitted by volcanoes, with the exception of lava; they come from different types of explosive eruptions. such as ash. A volcano is powered by one or more shells Magma. This magma derived from partial melting of the mantle. It is through chimneys or ducts that molten rock reaches the surface and the accumulation of these rocks can reach thousands of feet thick forming the mountains and even islands. According the nature of the materials, the type of eruption, their frequency and orogeny The orogeny (from the Greek oros, mountain, and genesis, training) means all the processes leading to the formation of mountain ranges. , volcanoes have various forms, in general they are conical mountains ending in a crater or caldera.
There are about 1 500 active volcanoes land which erupted sixty enter every year.
Image: The red volcanoes, effusive eruptions are relatively quiet, emit fluid lava in the form of castings, the volcanoes of "hot spot".
Image: The gray volcanic eruptions explosive issue pasty lava and ash in the form of pyroclastic flows and volcanic plumes
Erta Ale - Ethiopia
Image: Erta Ale Google map
The chain of Erta ale is among the axial channels in Afar, the largest and most characteristic. The Erta Alé is located in the north of the great rift valley in the Danakil Depression.
Currently there are two craters pits the crater North and South crater. The Erta Alé is one of the few active volcanoes in a lake of molten lava permanent, the heat from the washer reservoir is in equilibrium with the heat dissipated into the atmosphere.
Image: The lake of lava Erta Ale. It is one of three volcanoes in the world, with the Kilauea and Erebus, to contain a permanent lake of lava.
Lengai - Tanzania
Image: Ol Doinyo Lengai Google map
The Ol Doinyo Lengai is a Stratovolcano, i.e. a volcano whose structure is formed from the accumulation of lava, tephra of and / or pyroclastite, conical in shape because of his pasty lava which is hard sells. It is located in Tanzania, in the great rift valley that runs through eastern Africa from North to South. The Ol Doinyo Lengai ( "Mountain of Gods" in Maasai language) is located in northern Tanzania, 70 km from the Kenyan border and 160 km west of Kilimanjaro. This volcano, 370,000 years old, is one of the largest volcanoes in the region and amounts to 2 878 meters, not far from the famous Serengeti Game Reserve. Lengai, the only active volcano in this area, is also the only volcano on the planet to make carbonatites rich lavas sodium carbonate, iron and calcium, while other volcanoes spew lava globe mainly siliceous. The temperature carbonatites lavas exceptional and unique Lengai vary between 500 and 540 ° C, which is a low temperature compared to temperatures of basalts which are about 1 000 to 1 100 ° C.
In their emissions, these carbonatites are black like oil drain, then after a few minutes they become chocolate. A day later, these flows cooled deteriorate in contact with the atmosphere and the surface takes a white as snow. Its eruptions are rare, a dozen since the late 19th century. Since the last explosive eruption of 1966, which dug a crater 500 meters by 350 meters to 100 meters deep, the activity has resulted in the continuous outpouring of small lava flows that filled the crater. In 1999, flows have spread beyond the crater to slide down the slopes of Langa.
Image: The Lengai spits carbonatites rich lavas sodium carbonate, iron and calcium and low in silica.
Nyiragongo - Democratic Republic of Congo
Image: Le Nyiragongo Google map
The Stratovolcano or Niragongo Nyiragongo is one of the most active volcanoes and dangerous Africa.