Mount Nyamulagira Volcanic Eruption of January 2010


Introduction

Last erupting in 2006, Mount Nyamulagira is located in the Virunga National Park, north of Goma in Democratic Republic of Congo among the Virunga Mountains (figure 1). Standing 3,058 meters high, it is one of Africa’s most active volcanoes, erupting more than 42 times since 1885 and considered as a twin to Mount Nyaragongo, which lies about 12 kilometers southeast. Nyamulagira is a large, low silica containing, basaltic shield volcano. A shield volcano erupts fluid lava flows that can travel over long distances, creating broad, gentle slopes of about 10° to 20° near the summit. Near the base, the slope decreases to about 3°. With a summit caldera of approximately 2 km wide and a depth of 100 m, a lava lake is contained within the caldera during some eruptions. Shield volcanoes usually can hold a large volume of magma. The volcano has a volume of 500 km3, which is enough to cover 1500 km2 of the east African Rift. The East African Rift is the largest continental rift zone that is experiencing crustal extension. Two small towns, Goma and Sake are located about 20 km south of the volcano with about 800000 residents and refugees. Goma lies in a region that has been damaged by the years of fighting between the Democratic Republic of Congo government forces and rebellious armed groups.

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Figure 1:Mount Nyamulagira seen from above (Source #5)


Background

Mount Nyamulagira has eruptions inside the summit caldera, and is capable of producing fissures and cinder cones. Its eruption style is effusive, meaning lava flows as opposed to explosive eruptions. Basalt is a type of volcanic rock, which means the magma reaches the surface. It consists of magma with about 45%-55% of silica. This decreases the viscosity of the magma, making volcanic gas easy to escape and its eruption style fairly peaceful. Once basalt magma is cooled, it appears black to dark gray (figure 2). It can be composed of about 0.1% to 1.0% of water vapor, magnesium, iron, and is usually calcium-rich.

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Figure 2: Basalt volcanic rock (Source #2)

Recent Eruption
At 3:45 am on January 2, 2010, Mount Nyamulagira erupted and continued to spew ash and lava for two weeks. The lava flowed south, threatening the town of Sake, a major source of Goma’s fresh food. Local authorities were worried that the lava would flow into Lake Kivu, causing carbon dioxide and methane gas to be released quickly into air. This mixture of gas is flammable and can kill more than 1700 people as it did in 1986 at Lake Nyos.
Fortunately, the lava did not flow into the lake, but the continuous days of volcanic ash has endangered the health of locals. The local health center is treating more people suffering the effects of eating poisoned vegetation, causing cholera, diarrhea, and other diseases. The eruption has also been a problem for the livestock, such as cattle, because the grass is covered by black sand, pumice, and ash and the contaminated drinking water was also considered as another threat. Also within the Virgunga National Park, about 48 rare chimpanzees which lived near the volcano. The park is known as the oldest park in Africa, and home to 200 of world's last 750 mountain gorillas. Fortunately, the gorillas were located on the far eastern part of the park, and had no direct threat from this volcanic eruption.

Eventually, thousands of people fled to Rwanda, but returned the next week after the eruption has slowed. Those that returned feared becoming refugees in Rwanda, where officials refused to give the evacuees even a glass of water without charging them. They returned to a town without electricity, food, or clean water with their sleeping mats, suitcases, and clothing bundles. Crowds of people were breaking into shops looting the homes, taking what little was left when the town was evacuated.
Red Cross workers have estimated the death toll at 47 people as of January 21, 2010.



How the International Community helped the monitoring of the eruption
Since the 2002 volcanic eruption of Nyiragongo which destroyed Goma, the international community funded a volcanic observatory to monitor seismic and volcanic activity in the area so that people can evacuate safely. The scientists measure and survey fractures and the composition of gases using atmospheric sensors twice a month. These are the signals that magma gives when it rises to the surface, which give warnings of new eruptions. Other precursors used to forecast a volcanic eruption are seismic activity, surface temperature measurements, and tilt meters or remote sensing. A tilt meters measures the subtle swelling of a volcano by responding to the local acceleration of gravity.

Scientists, the United Nations, and local authorities have been using space images from the European Space Agency’s Envisat, seismic, and helicopter data to monitor the eruption hourly. Volcanologists need continuous data over long periods to evaluate the level of risk and increase their knowledge of volcanoes. For some areas or the Democratic Republic of Congo, using satellite is the only way to providing this information because the area is inaccessible or infested with violent rebel groups. The United Nations peacekeeping mission in Africa is using its aviation force. Also known as MONUC, they have sent their helicopters to the Volcanic Observatory of Goma and the National Institute for the Conservatory Nature to help monitor volcanic activity.

The satellite images provide valuable information to the Goma volcano Observatory, such as details about the lava flow, flow size, direction, and speed. From the satellite images, Dr. Nicolas d’Oreye of GORISK is able to confirm that the volcano is not showing any signs of abnormal activity. Dr. d’Oreye is also a senior scientist at the Geophysics and Astrophysics Department of the National Museum of Natural History in Luxembourg. Usually, lava flows from Nyamulagira are not threatening unless lava flows south of the volcano, which was what it was doing. Comparing satellite radar images, the old lava will appear bright white and new lava will appear black in after images if there has been lava flow (figure 3).


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Figure 3: Satellite radar images from Envisat from before and after the Nyamulagira eruption (Source #3)

Using “SAR interferometry” or InSAR, evaluating the differences between two radar signals taken over the volcano can show ground deformation due to the eruption. Colored rings represent ground movement. Putting the images together provides a detailed picture of the area and helps determine if there are any signs of volcanic activity.

Although several precautions are made to predict volcanic eruptions, the surrounding towns are heavily populated. The population of Goma has nearly doubled from 2002 to 2004, which would make it difficult to evacuate in the event of a threatening volcanic eruption.

Sources:
  1. "CVO Website - Africa Volcanoes and Volcanics." USGS Cascades Volcano Observatory (CVO). Web. 10 Feb. 2010. <http://vulcan.wr.usgs.gov/Volcanoes/Africa/description_africa_volcanics.html>.
  2. Basalt. Photograph. Austin. Bureau of Economic Geology. The University of Texas at Austin. Web. 17 Feb. 2010. <http://www.beg.utexas.edu/mainweb/publications/graphics/basalt.htm>.
  3. "ESA - Observing the Earth - Congo receives help from space after volcano eruption." ESA Communications Portal. Web. 10 Feb. 2010. <http://www.esa.int/esaEO/SEM3UUKOP4G_index_0.html>.
  4. "Nyamuragira volcano." VolcanoDiscovery: volcano adventure tours & travel. Web. 10 Feb. 2010. <http://www.volcanodiscovery.com/en/volcanoes/africa/nyamuragira.html>.
  5. Photograph. Google Earth. Google. Web. 17 Feb. 2010. <http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=goma,africa&sll=-1.977147,29.937744sspn=9.749295,13.392334&ie=UTF8&hq=&hnear=Goma,+North-Kivu,+Democratic+Republic+of+the+Congo&ll=-1.397872,29.236679&spn=0.610243,0.837021&t=h&z=11>.
  6. "Volcano erupts in Congo." Volcano erupts in Congo. CNN, 2 Jan. 2010. Web. 10 Feb. 2010. <http://www.cnn.com/2010/WORLD/africa/01/02/congo.volcano/index.html>.
  7. "Mt Nyamulagira volcanic eruption ." Servir Africa. N.p., n.d. Web. 16 Mar 2010. <http://www.servir.net/africa/index.php?option=com_content&task=view&id=717&Itemid=91>.