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Volcanowatch

April 16, 2009

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Central African metropolis again threatened by looming volcanic activity

Computer image of Nyiragongo volcano generated from satellite photographs, showing the Goma-Gisenyi conurbation on the lake shore in the foreground. In the background, left, is the Nyamuragira volcano.  Public domain Source: http://photojournal.jpl.nasa.gov/catalog/PIA03337
Computer image of Nyiragongo volcano generated from satellite photographs, showing the Goma-Gisenyi conurbation on the lake shore in the foreground. In the background, left, is the Nyamuragira volcano. Public domain Source: http://photojournal.jpl.nasa.gov/catalog/PIA03337

Life in Goma—a city of about half a million on the eastern border of the Democratic Republic of the Congo—has been particularly difficult over the past 15 years. Refugee crises, disease, and intense battles in and around the city have led to many thousands killed or displaced. Making matters significantly worse, the recent rumblings of Nyiragongo volcano, which lies just 16 km (10 miles) north, have no doubt reminded the city of the volcano's deadly past.

Following the Rwandan genocide in 1994, Goma was overwhelmed with refugees from across the border, leading to a severe humanitarian crisis and outbreak of cholera. Regional unrest continued, fueling the First and Second Congo Wars, in which battles were fought in and around the city. The Second Congo War was waged between 1998 and 2003, involving numerous African countries and leading to about five million deaths, mostly through disease and starvation.

While the Second Congo War was still raging, Nyiragongo began to stir. This vegetated stratovolcano is known for the persistent lava lake, active for most of the last century, within its summit crater. On January 17, 2002, fractures opened on the lower south flank of the volcano, and the perched lava lake rapidly drained out, producing fast-moving flows that swept through farmlands and, eventually, the city center.

`A`a and pahoehoe flows were channeled through city streets—burning buildings, igniting fuel depots, and burying a large portion of the city's airport and commercial district—before reaching Lake Kivu. Nearly 15 percent of the city was overrun by flows, effectively cutting the city in half. About 50 people were killed, and over a hundred thousand displaced.

The 2002 eruption was not, however, the first time that Nyiragongo's lava lake had drained with deadly consequences for residents. On January 10, 1977, following a steady rise of lava in the summit crater, fractures opened and sent out unusually fast-moving flows that swept through nearby villages, killing at least 70 people. These were perhaps the fastest moving lava flows ever recorded, with observers estimating speeds up to 60 km/hr (40 mph). These high velocities were due to Nyiragongo's exceptionally fluid lava, which results from very low silica content.

With these events in mind, the recent increase in activity over the past few months must be a source of great anxiety in the city. Goma Volcano Observatory, the agency responsible for monitoring Nyiragongo and its active neighbor, Nyamuragira, reported a seismic swarm in January and increased seismicity since then. A report on Nyiragongo last week noted an increase in fumarolic activity, higher temperatures in fissures, as well as gas plumes from the summit.

Nyiragongo occasionally experiences periods of unrest that do not lead to eruptions, so it is too soon to tell whether another eruption is imminent. Another complication is that some of the seismic activity may be originating from Nyamuragira.

As volcanic unrest has increased over the past few months, political stability remains elusive. Armed forces approached Goma in October 2008 and fought battles on the city's outskirts, while looting and violence gripped the city. Following a ceasefire, talks are now in progress to try to reach some semblance of peace. Active volcanoes, however, can't be negotiated with, and only time will tell whether another major eruption will affect this already strained city.

Activity update

The Waikupanaha and Kupapa`u ocean entries remain active, with small littoral explosions common at Waikupanaha over the past week. Surface flows inland from Kupapa`u remain active along the eastern boundary of the National Park.

At Kīlauea's summit, the vent within Halema`uma`u Crater continues to emit elevated amounts of sulfur dioxide gas, resulting in high concentrations of sulfur dioxide downwind. Variable glow and vent noises over the past week suggest that lava is still present at shallow levels below the floor of Halema`uma`u crater.

A magnitude-5.0 earthquake at 12:44 p.m. H.s.t. on Tuesday, April 14, was located beneath the central part of Kilauea's south flank, about 12 km (8 miles) southeast of Kilauea's summit and at a depth of 10 km (6.2 miles). More than 650 people reported feeling it (http://earthquake.usgs.gov/eqcenter/dyfi/events/hv/00033612/us/index.html).

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea summary; email questions to askHVO@usgs.gov. skip past bottom navigational bar


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Updated: April 21, 2009 (pnf)