Volcanoes of Colombia

The Andes cordillera is the highest mountain chain in the world (7100 km long), it is located along the western coast of South America through Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina.
Its average altitude is 4000 meters and its highest peak is Aconcagua, located in Argentina, which rises to 6962 meters. Many summits are volcanoes Volcano: volcanism definition given by an American geologist: "This is all the physico-chemical phenomena that accompany the ascent of magmas."  created by the passage (subduction) of the Pacific plate under the South American plate.
The main mountains Colombies are: Pic Cristóbal Colón (5775 m), Simón Bolívar Peak (5775 m), Ritacuba Blanco (5410 m), Nevado del Huila (5365 m), Nevado del Ruiz (5321 m) , Nevado de Quindio (5215 m), Nevado del Tolima (5200 m), Galeras (4276 m).
There are about 1500 active volcanoes on Earth including sixty erupt every year. Volcanoes can be at the origin massive climate disasters, causing a sudden cooling of the Earth's average temperature.
A volcano is composed of three parts: a reservoir of magma at depth, one or more volcanic vents which communicate with the interior of the Earth, and the volcanic mountain which is either a crater, a crater cone or dome or a lava flow or a product deposit of explosion (ground pumice, etc.)..
Volcanic eruptions give birth to popular beliefs mingled superstitious terrors and fantastic legends. It is true that some eruptions can be catastrophic to the point of disappearing civilizations.
The main active volcanoes are: Cerro Machin volcano (2750 m), the volcano Nevado del Ruiz (5320 m), the volcano Nevado del Huila (5365 meters) and the Galeras volcano (4275 m).

Cerro Machin volcano is located 150 km southwest of Bogota, 17 km west of Ibague, 30 km east of the city of Armenia on the eastern slopes of the Cordillera Central. Cerro Machin is in a warm temperate region with an mean temperature of 20°C, annual rainfall of 1150 mm, the average relative humidity is 85%, the dry and rainy seasons usually alternate during year.
Cerro Machin has the lowest altitude volcanoes in Colombia (2750 m). Although it has not been an eruption since the year 1180, it is an active volcano.
The center of the crater 2.4 km in diameter, is occupied by several domes with fumarole activity and hot springs. In this explosive volcano crater, there is a beautiful crescent-shaped pond. In the center ring of the volcano there are three domes which reached the highest altitude of 2750 m, the highest point of the volcano. The entire surface is covered by small tributaries of the Magdalena, the most important river of Colombia. It flows in a wide valley between the Cordillera Central and Eastern Colombian Andes, to the north across the country. Cerro Machin volcano is located on the southwestern margin of the volcanic complex called Machin on the eastern side of the Cordillera Central are found the Cerro Bravo.

Cerro Machin currently asleep, could wake up in a huge explosion as in the past.
The domes are actually plugs volcanic vents which are drawn in the ancient explosions, pyroclastic ash that tephras The tephra represent all materials (solids and liquids, driven by gases) emitted by volcanoes, except lava, they come from different types of explosive eruptions., such as pyroclastic ash and pumice, pyroclastic flows and boulders and mudslides called lahars.
Mudflows or lahars, are usually devastating power, they descend the mountains and devour everything in their path, trees, bridges, cars, buildings, etc.
Volcanic activity Machin volcano has increased since 1998, small earthquakes and fumaroles are becoming more numerous.
Geologists are attentive to radon gas emissions and possible deformations domes that obstruct the crater.
How long these plugs retain the magma reservoir situated below?

NB: A lahar is a mudflow of volcanic origin. It is mainly composed of water, volcanic ash and tephra.

The Nevado del Ruiz covered by glaciers, is a volcano of the Andes, with its 5300 meters, it is one of the highest in Colombia. It is also the second most active volcano Galeras after.
Glaciers around the crater Arenas.
The Nevado del Ruiz was formed by a subduction volcanism and had frequent plinian eruptions during the Holocene, i.e. from the last 10 000 years. But it was in 1985 was the site of one of the most deadly explosions in Colombia. It has almost completely destroyed the city of Armero. Since the monitoring of this volcano is constant, hundreds of thousands of people living in the surrounding valleys. After 69 years of rest, the Nevado del Ruiz erupted 11 September 1985 until 13 July 1991.
The lahar engulfed part of the town of Armero in the night of 13 to 14 November 1985, killing in their sleep, nearly 20,000 of the 29,000 inhabitants of the city. It was a nightmare scenario for pyroclastic flows from the crater prevailed glaciers melted snow and four enormous lahars streaming down the sides of the mountain at 60 km/h.
Lahars down in the beds of the six rivers of the volcano and covered the town of Armero.
The world remembers the video images of Omayra Sánchez small, 13 years old, dying in a viscous mud.

The mud made ​​it almost impossible advance rescue without the risk of getting bogged down and it took rescuers two hours to respond that left no chance to seriously injured victims.
Images of disfigured bodies and houses completely destroyed, were horrible.
In the twentieth century, only the eruption of Mount Pelee was more deadly with 29,000 deaths.
A gigantic eruption of Nevado del Ruiz could reach Bogotá. This is why the Colombian government has established a careful monitoring of this stratovolcano The stratovolcano is a volcanic mountain that is formed by the accumulation over the eruptions of lava and ash levels. The stratovolcano is an explosive volcanism volcano, which is characterized by very steep slopes, and the presence of a dome at the top, made of lava very viscous and filled with gas. Etna, Sicily, Kilimanjaro, Tanzania, and Merapi, on the island of Java in Indonesia are examples of stratovolcanoes. .
On 4 January 1986, 15,000 people were evacuated after a moderate but no explosive phase is triggered lahar. The evacuation is renewed in March 1989 and since seismic activity and SO2 emission rates are low to moderate.

NB: A Plinian eruption is a type of volcanic eruption, lava emission viscous, which occurs on gray volcanoes. This lava mouth and the volcanic vent internal pressure increases in the volcano to cause huge explosions that can destroy the volcano itself and give birth to a caldera.

The Nevado del Huila is a moderately active volcanic complex consists of several stratovolcanoes and domes. It is located in Colombia in the department of Huila, in the central Andes.
This is the highest volcano Colombian Andes (between 5364 and 5750 meters) and therefore as the highest volcanoes in Colombia it is covered by an ice cap.
This volcano is built in an ancient caldera ten miles in diameter where several volcanic domes emerge, Pico Norte, Cresta Pico, Pico Central and Pico Sur.
Volcanism of the Nevado del Huila has produced six volcanic cones whose age decreases from south to north. This is actually a huge sprawling mountain sixteen miles long and seven miles wide.
His training took place over two distinct periods, so there Huila Huila current and former mainly effusive.

Traces latest activity are on the Pico Sur, in the form of domes. The only activity is the sound of his snoring permanently. It should however be wary of sleeping giants.

Image The Nevado del Huila volcano is a huge complex of moderately active Colombian Andes.

The Galeras volcano is a stratovolcano in the Andes in the Colombian department of Nariño, about 9 km from the capital San Juan de Pasto. The Indians gave him the name "Urcunina" i.e. Mountain of Fire, then the Spanish conquerors called it "Galeras" for its resemblance to the galleys or sailing ships sailing in the Mediterranean.
The Galeras volcano is best known as a volcanic complex (CVG), it has a conical shape and the western part of the edifice is destroyed.
Its summit stands at 4276 meters altitude. It erupts frequently, since its eruption history of December 7, 1580. It is currently the most active volcano in Colombia, followed by the Nevado del Ruiz.
The Galeras volcano has been active for at least a million years, spewing mainly andesite.
Large eruptions built the ancient caldera wall, part of which is now collapsed. Inside the caldera there is a small cone-shaped horseshoe. Its dangerous activity concerned the 450,000 residents of San Juan de Pasto.

NB: Andesite is a volcanic igneous rock, gray. It is characteristic of subduction zone volcanism.