By Jesper A.C. Kofoed, UNEP-DEWA, 230102.
The Mt. Nyiragongo is one of two active volcanoes situated in the Main Rift Zone of the African Rift Valleys. It is situated 18 km N of Goma. Together with its sister volcano Nyamuragira 10 km further north. The two volcanoes have a history of relatively abundant eruptions (more than 50 in the last 150 years!).
Nyiragongo is a so-called stratovolcano having three summit craters. The ongoing eruption is a flank eruption with lava being extruded from 3 fissures in the southern flanks of the volcano, causing three flows that down stream join into a single main flow.
The town of Goma by the shores of Lake Kivu was reached by this flow only a few hours after the eruption started. Today on 23/01/02 the lava is still flowing very slowly into the lake, through lava tubes of solidified lava where a thin crust is isolating the red-hot lava from the cooling air. People started dangerously early to walk on this thin crust trying to cross the lava flow that have cut the town in two.
Water vapour is rising into the air, where the lava reaches the lake, and here the temperature of the lake water has locally reached temperatures well above normal. There are no poisonous gasses entering the lake waters from the lava, same as for the air above the lava flows in the city.
The Lake Kivu is a well-studied lake, it is known to contain large amounts of natural volcanic gasses originating from the earths mantle; the gasses are mainly CO2 and methane. The gasses are constantly accumulating in the lake and are as such not directly related to the current eruption.
A general fear amongst scientist studying the lake is that large masses of lava entering the lake could possibly stir up the bottom waters containing large amounts of dissolved gasses, these gasses would then by released from the water as a result of changes in pressure and temperature as the water is being brought up near the surface. This would most likely happen very rapidly in a catastrophic event as seen by e.g. Lake Nyos, Cameroon in 1986, where more than 1700 humans died from CO2 suffocation following a large gas-release from the lake. Other factors thought to be capable of triggering a release of gas from the lake, are strong earthquakes and high inflows of cold river water during torrential rains. So far there is no historical record of a volcanic eruption causing this lake to release CO2.
Today expert vulcanologists are on the site studying mainly the eruption but also the lake. There is a general consensus amongst these scientists that the eruption most likely is ebbing out and that the volcano is going towards another dormant period. This is based on assumptions and superficial observations made on the volcano.
It must be stressed that there are currently no measuring equipment installed on the mountain and no functioning volcanological observatory in the area capable of supplying the scientists with numerical data on the evolution of the volcano, and therefore precise and temporal predictions as to the risk of future eruptions cannot be made.
There are many environmental implications of such an eruption although these should not outshine the immediate humanitarian crisis amongst the 400000 people directly affected by the eruption.
One of the main concerns from an environmental perspective
is what will happen when people turn to the forest to collect fuel wood,
food and to find shelter. It has been reported that already an estimated
200000 people have moved into the forests of the Virunga Mountains.
These forests are in some areas previously largely unaffected by human
activities and form the habitat of many endangered species e.g. the
Mountain Gorilla (Gorilla gorilla). Fortunately the nearby Ugandan Gorilla
Sanctuary lies in the opposite direction as to the current lava flows,
and this area is therefore not likely to be affected by the volcano
unless new eruptions start extruding lava from the northern flanks of