Volcanoes in Africa
Characteristics of a volcano
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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.
The eruption fate of the volcanic chimney typically located at the top, but there are openings that appear on the flanks of the volcano like Mount Etna.
Volcanoes are classified into two types:
- the "red volcanoes' with effusive eruptions relatively quiet, emit lava fluids in the form of slides, the volcanoes of" hot spot "volcanoes and submarine ocean ridges,
- the" gray volcanoes "to explosive eruptions, emitting pasty lava and ash in the form of fiery clouds (or pyroclastic flows) and volcanic plumes.
There are about 1 500 active volcanoes land which erupted sixty enter every year.
The word "volcano" comes from Vulcano, one of the Aeolian islands named in honor of Vulcan, the Roman god of fire. Its equivalent in the Greek pantheon is Hephaestus.
For the Romans, Vulcan is one of three son of Jupiter and Juno. Vulcan reigned supreme in the bowels burning volcanoes.
That is why it was taken for the patron saint of blacksmiths as the caption said it had installed its forges into the depths of the crater Vulcano.
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
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Erta Ale - Ethiopia
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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.
Erta Ale means smoking mountain in Afar.
It measures, from north to south, over 95 km long and 42 km wide. It is located along the axis of the northern part of the Danakil Depression, descending to - 120 m below sea level, Ethiopia, near the Red Sea. It includes six buildings volcanic Erta Ale, Gada Ale, Alu-Dala Filla, Boral Ale, Hayli GUB, Alé ring.
This desert area with no vegetation is the area of lava.
The Afar depression, called Dancalie or Danakil in the north, is an area at the intersection of three boundaries of lithospheric plates, is the meeting place of three rifts, the Ethiopian rift continental rifts and two ocean the Red Sea and Gulf of Aden.
The active volcano, Erta Alé is only 613 meters heart of the volcanic chain of Erta Ale. It is a shield volcano, 600 m high slopes very low, supported by a base of 30 km in diameter.
His summit with the morphology change depending on volcanic activity, has a caldera collapse (1 600 x 700 m) as that found on the summit of Mauna Loa or Kilauea in Hawaii. Its elliptical caldera is stretched by a north-north-west to south-south-east. Within this caldera crater is called Pit (pit crater), with steep walls, which, depending on the activity, one or more lakes of molten lava.
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.
The southern crater has a diameter of 140 meters and a depth of 90 m filled by a lake of lava, whose depth varies.
Sometimes, as was the case in February and April 1972, the lake of lava rising pit crater and beyond: lava flows expand then on the floor of the caldera. This active volcano is little known and difficult to access. The first ascent by a European date of 1873.
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
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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.
The steep and arduous ascent of the volcano Oldonyo Lengai takes 5 to 7 hours of walking in a remote area in the heart of the Rift Valley in Tanzania.
Image: The Lengai spits carbonatites rich lavas sodium carbonate, iron and calcium and low in silica.
Nyiragongo - Democratic Republic of Congo
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The Stratovolcano or Niragongo Nyiragongo is one of the most active volcanoes and dangerous Africa.
The Nyiragongo is located in the great Rift Valley, east of the Democratic Republic of Congo near the Rwandan border. The closest cities are the Congolese town of Goma and the Rwandan town of Gisenyi.
The Nyiragongo threatening rises to 3 425 meters and its crater measuring 1.2 kilometers in diameter.
On 17 May 2002, a new lava lake formed in the crater, still active in 2008. It is constantly stirred and kept liquid by the daily rise of gas bubbles of sulfur dioxide.
In 2002 the river of lava had reached the city, cutting into two before joining the Lake Kivu.
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