Mount Nyiragongo eruption in The Democratic Republic of Congo

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Thousands of people fled by a volcanic eruption in the Democratic Republic of the Congo from Mount Nyiragongo outside the city of Goma. Without warning, Nyiragongo Mountain turned the dark sky fiery red on Saturday night and then spewed lava flows into villages that destroyed more than 500 homes in the town of Goma near Goma International Airport, officials and survivors said. 

What is Volcano?

A volcano is a place where gases, ash and / or molten rock material – magma / lava escape to the ground. In the process, molten rock, called magma in the asthenosphere, comes to the surface where it is called lava. 

Causes of volcanism 

• Due to the different levels of radioactivity, there is a large temperature difference between the inner and outer layers of the earth. 
• This temperature difference leads to convection currents in the mantle. 
• Convection currents in the mantle create convergent and divergent boundaries (weak zones). 
• In the case of divergent boundries, the thinning of the upper crust leads to a reduction in the overlay pressure of the rocks, which results in a decrease in the melting point of the rocks and the formation of magma, which rises and erupts as fissured lava volcanoes. For example: Mount Nyiragongo, Mid-Atlantic Mountain Range.

• Subduction of one plate under another with a convergent plate boundary and the resulting melting of the rocks due to the high temperature and the pressure increase along the fissures of rocks. Example: Barren Island (India) .

Types of Volcanoes
Volcanoes are classified according to the type of eruption and the shape developed on the surface.

Shield volcanoes 

• Shield volcanoes are, apart from basalt flows, the largest of all volcanoes on earth. 
• Hawaiian volcanoes are the most famous examples. 
• These volcanoes are mainly made of basalt, a type of lava that is very fluid when it erupts, so these volcanoes are not steep. 

composite volcanoes: 

• These volcanoes are characterized by lava eruptions that are cooler and more viscous than basalt. 
• These volcanoes often lead to explosive eruptions. 
• Large amounts of pyroclastic material and ash reach the ground with lava. 
• This material accumulates near the vents that create layers, making the mountains appear as composite volcanoes 

Caldera: 

• These are the most explosive volcanoes on earth. They’re usually so explosive that when they break out, instead of building a tall structure, they tend to collapse on themselves. The collapsed depressions are called calderas. 

Basalt flood provinces (fissure like volcanoes) 

• These volcanoes shed very liquid lava that flows over long stretches. 
• The Deccan Traps of India, which currently cover most of the Maharashtra Plateau, is a much larger basalt flood province.

Based on eruption frequency: 

Dormant volcano: Volcanoes that show signs of a possible future eruption are said to be dormant. For example: Kilimanjaro in Tanzania, also the highest mountain in Africa, is known as a dormant volcano.
Extinct volcanoes: Volcanoes that did not erupt in historical times but retain the properties of volcanoes are referred to as extinct, for example: Deccan Traps, India.
Active Volcanoes: Volcanoes are considered active when they erupt frequently and are mainly found around the ring of fire.
Example
Mount Nyiragongo 

Nyiragongo (also spelled Niragongo), one of the most active volcanoes in the world, is a large stratovolcano with an altitude of 3470 m (11,385 ft) in the Virunga Mountains, connected to the Albertine Rift near the Kivu Lake on the eastern border of the Democratic Republic of the Congo with Rwanda in the Virunga National Park. It has a caldera 1.2 km in diameter that contains the largest and most active lava lake in the world. Nyiragongo and nearby Nyamuragira are together responsible for 40 percent of Africa’s historic volcanic eruptions

The Albertine Rift is the result of tectonic movements that are gradually separating the Somali plate from the rest of the African continent. It starts at the northern end of Lake Albert to the southern end of Lake Tanganyika

Distribution of volcanoes in the world

• Most of the volcanic activity known to us occurs along the edges of convergent plates and mid-ocean ridges. 
• About 480 volcanoes have been reported as active since the 16th century. 

• Of the 480 reported volcanoes, nearly 400 were discovered in and around the Pacific Ocean and 80 in the mid-world belt over the Mediterranean Sea, the Himalayan Alpine Belt, and in the Atlantic and Indian Oceans.