Volcanic Hazards:
Although erruptions of Africa's many volcanos may not be in this week's headline news, the high population density in the fertile plains surroundnig them makes them a considerable hazard. Records of volcanic activity in the region go as far back as the 5th century B.C.E., but they are spotty at best until the advent of exploration following the opening of the Suez canal in 1869. Three of the four recorded large eruptions were over 2000 years ago, but with so many Holocene pyroclastic cones, the dangers associated with small eruptions--like fires are still a threat.
The East African rift created Africa's highest and lowest elevation volcanoes, from Kilimanjaro's three-volcano system, to the vents below sea level in Ethiopia's Danakil Depression. Also in Ethiopia are the lava lakes of Erta Ale, popular for their longevity.
Two neighboring volcanoes in Virunga National Park, Nyamuragira and Nyiragongo, are responsible for nearly two-fifths of Africa's historical eruptions.
Helicopter view (in February 1994) of the active lava lake within the summit crater of 'Erta 'Ale (Ethiopia), one of the active volcanoes in the East African Rift Zone. Two helmeted, red-suited volcanologists -- observing the activity from the crater rim -- provide scale. Red color within the crater shows where molten lava is breaking through the lava lake's solidified, black crust. (Photograph by Jacques Durieux, Groupe Volcans Actifs.)
Erta Ale:
- Isolated basaltic shield volcano - most active volcano in Ethiopia.
- 50-kilometer-wide volcano rises 613 meters from below sea level in the Danakil depression. Contains a 0.7 x 1.6 kilometers, elliptical summit crater housing steep-sided pit craters.
- Lava lakes-- Basaltic lava flows from these fissures have poured into the caldera and locally oveflowed its rim. The summit caldera is renowned for one, or sometimes two longterm lava lakes that have been active since at least 1967.
- Recent fissure eruptions have occurred on the northern flank of Erta Ale.
Mount Kilimanjaro:
- 19,340 feet (5895 meters) is the highest and most famous mountain in Africa
- Located in Tanzania just adjacent to the Kenya border
- Three distinct volcanoes overlapping flow appear as a single feature
- Kibo (center volcano) with the highest peak and a permanent glacier and snow field at its summit;
- Shira (most west), the oldest that has been eroded into a plateau-like feature standing 12,395 feet (3778 meters) above sea level; and
- Mawenzi (most east) with a well-defined peak that reaches 17,564 feet (5354 meters) above sea level.
Nyamuragira and Nyiragongo:
- Responsible for nearly two-fifths of Africa's historical eruptions.
- Nyamuragira
- Africa's most active volcano
- Massive basaltic shield volcano
- North of Lake Kivu northwest of Nyiragongo volcano.
- Volume of 500 cubic kilometers
- Extensive lava flows from Nyamuragira cover 1500 sq. km of the East African Rift
- 3058 meters high
- 2 x 2.3 km summit caldera with walls 100 meters high
- Historical eruptions occurred within the summit caldera
- Modifying the morphology of the caldera floor
- Numerous fissures and cinder cones on the flanks of the volcano
- Lava lake in the summit crater, active since at least 1921, drained in 1938
- Recent (20th centry) lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu
Seismic Hazards:
Illustrsted on the above USGS graphic, the Seismic Hazard along the Great Rift Valley (although higher than elsewhere in the continent) is still only low to moderate. Many frequent but small earthquakes happen often associated with the normal faulting in the rift basin, but these pose no significant hazard.
Links
Website is for educational purposes only.
Last Updated May 2, 2005.