26.07.2012

Explore volcanoes on Wikimapia Pt.2

Today we continue exploring volcanoes from around the world with Wikimapia. African continent has drawn our attention this time. Most African volcanoes resulted from hotspots or the rifting in Earth crust, or a combination of both reasons.


The East African Rift

The East African rift, one of the world's most dramatic extensional structures, has produced the continent's highest and lowest volcanoes, ranging from the massive Kilimanjaro to vents in Ethiopia's Danakil Depression that lie below sea level. The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. The rift is a narrow zone in which the African Plate is in the process of splitting into two smaller tectonic plates. If you switch on “volcano” category and watch East Africa you’ll notice the contour of the rift right away as the red marks that show volcanoes will be grouped in the eastern part of the continent in a line.

The highest mountain in Africa is Kilimanjaro - the dormant volcano from Tanzania with three volcanic cones. Its highest peak Unuru is 5,895 metres above the sea level. There is a permanent snow pack on the peak. The second peak Mawenzi (height 5.354 m.) its located on the righ of Uhuru. Estimated to be 12 sq km in 1900, the ice cap on the highest point in Africa is now only 2 sq km. One of the most visible signs of global warming, the snows of Kilimanjaro have dwindled some 80 percent in little more than a century. Ice has also thinned significantly, leading scientists to believe the famous sight could be gone by 2020. Now that is something to think about.

Mount Kilimanjaro

Mount Cameroon is an active volcano in Cameroon near the Gulf of Guinea. It is just a bit lower than Kilimanjaro and is 4,**** m high. More than 100 small cinder cones, occur on the flanks and surrounding lowlands of the volcano. A large satellitic peak, Etinde (also known as Little Cameroon), is located on the southern flank near the coast. Historical activity, the most frequent of west African volcanoes, was first observed in the 5th century BC by the Carthaginian navigator Hannon. During historical time, moderate explosive and effusive eruptions have occurred from both summit and flank vents. Eruption in 1922 produced a lava flow that reached the Atlantic coast, and a lava flow from a 1999 eruption stopped only 200 m from the sea.

Mount Cameroon

Mount Elgon is a huge, ancient, and eroded stratovolcano which sits astride the Uganda-Kenya border. Although not the tallest of the isolated volcanoes of East Africa, it is among the largest in volume, rising up from a base over 80 km in diameter on the plains at about 1200 m elevation. Elgon is topped by a caldera about 8 km in diameter, with several high points over 4000 m along the rim. Elgon is noted for its unique Afro-alpine trees and plants, and for the many caves in its mid-elevation slopes, where elephants and other large animals can often be found eating mineral salts. These caves are not lava tubes, since Elgon has few suitable lava flows, but are instead eroded from the volcanic tuff (welded ash flows) which make up the bulk of Elgon's volume (digging by elephants may also contribute to the enlargement of the caves).

Mount Elgon

In Africa except the already familiar to us but none the less striking volcanoes you can find some volcanic places that you couldn’t ever see in Europe. And I’m speaking about lava lakes.

In Democratic Republic of the Congo, Virunga National Park, mount Nyiragongo is situated. Nyiragongo volcano is one of the most active volcanoes in Africa. Its main crater is about two km wide and usually contains a lava lake. The crater presently has two distinct cooled lava benches within the crater walls - one at about 3175 m and a lower one at about 2975 m. Nyiragongo's lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably. A maximum elevation of the lava lake was recorded at about 3250 m prior to the January 1977 eruption, lake depth of about 600 m. Nyiragongo and nearby Nyamuragira volcanoes are together responsible for 40% of Africa's historical volcanic eruptions. On the satellite photo you may even see the smoke from the lava lake rising high.

Mount Nyiragongo Lava Lake

Erta Ale ("smoking mountain" in Afar) is an active shield volcano in the Afar Region of northeastern Ethiopia. It is the most active volcano in the country. Erta Ale is 613 metres tall, with a lava lake, one of only five in the world, at the summit. It is notable for being the longest existing lava lake, present since the early years of the twentieth century. It is known locally and in lore as a "gateway to hell". Erta Ale is located in the Afar Depression, a desert area spanning the border with Eritrea, and the volcano itself is surrounded completely by an area below sea level. On this satellite picture you can even see the result of overflowing lava - long black lava traces.

Erta Ale

The next volcano disproves the stereotype that volcanoes are always high mountains.
The Danakil depression is one of the world's most extraordinary places, where giant tectonic forces rip the Earth crust apart. Active volcanoes, deep depression and infinite salt deposits are the result. The Danakil is one of the most hostile and fascinating places, but also home to one of the richest salt deposits. For thousands of years the salt has been being faught over here, exploited and exported. It is ruled over by the proud tribe of the Afar. Up to today, this work is being done as in biblical times. The craters of Danakil are the lowest known subaerial volcanoes. The most recent of these craters, Dallol, lies 48 m below sea level and was formed during an eruption in 1926. Colorful hot brine springs are found in the Dallol area.

Dallol

Another interesting natural volcanic phenomena is a volcanic field. A volcanic field is an area of the Earth's crust that is prone to localized volcanic activity, it usually contains 10 to 100 volcanoes and is usually in clusters. Lava flows may also occur. A volcanic field is probably a perfect place for filming a movie about the Moon. Natural decorations are ready and waiting for a brave film director for thousands years!

Jabal Meidub Volcanic Field is situated in western Sudan. Basaltic scoria cones are scattered throughout the field, their lavas have produced a broad lava plateau. The youngest dated eruptions about 5000 years ago produced a tuff ring and a lava flow. But this is only the one of many volcanic fields in Africa. Here is Mega Basalt Vulcanic field, straddling the Ethiopia-Kenya border. These two neighbor volcanic fields are also very picturesque.

Jabal Meidub Volcanic Field

Unfortunately, the largest part of the amazing volcanoes is hard to visit. You either need to be an experienced mountaineer or find a save guide and be prepared physically for a long journey in desert. But gladly that doesn't mean, that just a "man of mould" will never enjoy the beauty of African volcanoes.
Volcanoes National Park, which is situated in northwestern Rwanda, is a perfect place for inquisitive tourists! On the territory of the Volcanoes National Park the very rare, and endangered species of mountain gorillas (Gorilla beringei beringei) are living on the slopes of the vulcanoes. Moreover, there are some picturesque lakes and caves to visit.
Just not far from Volcanoes National Park is The Virunga National Park, formerly named Albert National Park, which a tourist can also visit. Although the volcanoes in national parks are not the biggest, they are probably much more suitable for tourism.

Volcanoes National Park

As you may see, Africa is a continent, that is full of volcanoes. All, that are mentioned in this article, are already marked on Wikimapia, but their description will be certainly improved, if you find them and add more photos and information. But even a larger part of volcanoes are left unknown and await their turn to be revealed to Wikimapia Community.