Dallol (volcano)

Dallol is the name of an area of the Afar, but also of a crater single Volcanique in the world. Being in North Is Ethiopia, in the Dancalie, this volcanic crater, produced after the explosion of important a magmatic Chambre of the rift to the top of a vast zone saltworks in the west of the Red Sea, is below the level of the ocean, in the depression of Danakil. It reigns there a heat côtoyant the 60°C with 40°C in the shade.

This vast sorry zone is known for its curious geological formations: single geological formations, acid hot sources, sulfur mountains, solidified salt columns, small gas geysers, basins of acids isolated by salt cornices and concretions from évaporite S, Sulfur, Chloride magnesium, Brine and Soda solidified. The whole on a zone white, yellow, green and red ocher, due to the strong presence of sulfur, Oxide iron, salt and others Mineral.

The site, following the example volcanos surrounding this zone (Erta Ale, volcanos of the Kenya, etc) is the result of the spacing of the Arabic plate and the African plate and the creation of the rift of the Red Sea.

History

The last eruption of this volcano was of type phreatomagmatic, and goes back to 1926.

The volcano was ignored for a long time of the public, contrary to the Erta Ale, and only some volcanologists knew the site. It is only into 2001 that the zone was officially accessible to all, and in 2004 which one made take knowledge of this volcano to the general public. The volcano does not appear in the majority of the books of volcanology and geology, even current.

Its discovery by the first European colonists surely dated from the first colonizations and the first forwardings in the area, with XVIIe or XVIIIe centuries. But hostility of the depression, the unbearable heat which reign there and the danger of the site (acid basins, toxic fumes…), did not have to support forwardings in the zones close to the crater. On the contrary, Erta Ale was much more accessible, in particular because the part of the rift where Erta Ale (Appelé Erta Ale Arranges) is definitely higher.

This site is unfortunately not classified yet national park, alone its insulation protects it from the visitors. A project of national park is in hand. The site is visited little because of the war between the Ethiopia and the Érythrée which always threatens the country, but the incursions are done increasingly current. However, it is disadvised attending the area as tourists, because of the conflicts which threaten.

Geology

The volcano, vast zone saltworks whose edges are roughcast hundreds of chimneys of fairies, shelters innumerable sulfur hot sources, geysers, fumerolles, deposits of salt and sulfur, concretions, terraces and run. The salt of the depression mixes with volcanic minerals, like sulfur, to create single terraces and concretions.

One can see in certain hot sources of the volcano of small castings of salt and brine with 100°, of small castings of bischofite molten, even of run liquid sulfur. These substances leave the chimneys and geysers which decorate the site.

Sometimes, from pollutant gases emanate from the fumerolles and the geysers. It is not rare to find corpses of small animals isolated in the crater. Moreover, certain unstable funds dissimulate acid basins which are frightening traps for animals and human. Another characteristic, the small geysers which do not resemble nothing known. Have can see permanent gas gushings on the surface of ponds of acids or geysers in saline the crystal sponge shape from which leave the warm water droplets with strange a gargouillis.

Chimneys of salt fairies create the relief of the crater, conferring on the volcano a strange aspect. These geological buildings were formed when the Red Sea flooded on several occasions the depression, several thousands of years ago. The passage of the sea built saline deposits around the volcano, and the evaporation of the water combined with the absence of winds, has, with time, formed these columns of soda.

Dallol is single since it is about the only place in the world where such formations exist. However the Erta Ale Arranges knows other sulfurous formations not far from Dallol, (like the crater of the Ash Ring, for example) in the craters of certain small auxiliary volcanos filled of basins saltworks and bubbling acids.

Various concretions of the crater

One can observe in the volcano of the Concrétion S of sulfur, of salt and other minerals which level in the hot sources. The origin of these mineral buildings is multiple. Strong acidity and strong salinity around the volcano make re-appear concretions due to the strong presence of Chlorure of magnesium, sulfur, Potasse and Saumure molten liquid and Bischofite which, crystallized, creates various concretions of the site. Great brine rates dispersed in the Acide create also crystallized flowers of salt. The conditions desert and isolated from Dallol encourage the formation of évaporite S, persons in charge of the appearance of concretions of any kinds. Formations saltworks, resembling egg shells, decorate certain zones of the crater.

Concretions saltworks

When isolated water levels know a rate of salinity higher than the average (Dead Sea, Lac Assal…) salt concretions tend to be formed on the banks of these lakes, often building the shapes evoking of mushrooms or the stalagmites, as well as evaporitic concretions and " corniches" of solidified soda. In Dallol, the same case occurs, but these saline buildings, instead of being formed in alkaline water, bathe in the acid. This is why concretions adopt yellow, green and orange colors, because of the sulfur which settles there.

Sulfurous concretions

Sulfur in great concentration is also responsible for the creation of crystalline concretions, mainly around active mouths fumerolliennes. Thus one observes close to the sulfur springs of the kinds of large " fourrures" of sulfur yellow or orange crystallized which can in certain cases measure nearly one meter. One can also note the presence of concretions in form of " shells of oeufs" around the old deposits.

Other concretions and phenomena saline and sulfurous

Some of these Concrétion S point out in particular the formations Calcaire S which one can find in the Grotte S and the Gouffre S. Indeed, the geological layers, crystallizations and other formations are formed in the same way; whereas concretions of the caves are formed by the Calcite worked by the acid of subterranean water during the hundreds of years, in geologically isolated zones, concretions of Dallol are formed by the soda and sulfur solidified worked by the sulphuric Acid of the hot sources. Concretions are not degraded, in the absence of winds and of biological activity, and can be formed easily according to these remarkable geographical conditions. But there exist differences in many points; initially, concretions of Dallol are formed much more quickly, concentrated acidity and heated water accelerating erosion. And in any event, the geological compounds are not the same ones. Whereas the layers and platforms which one can find in caves are made of calcite and are filled with ground water basins, the terraces of Dallol are formed by salt and sulfur and are filled of pure acids.

Human activity

There does not exist currently any human activity in the site. Only the Afar S live around the crater, from where they extract salt from the plains saltworks and carry it to the capital with back of Dromadaire. No geothermic activity for thermal industry.

Let us note that there exists in the crater a phantom Ville, old factory of extraction of Potassium used by the Italian S during the invasion of the country by Mussolini, then abandoned in the neighborhoods of 1930. Re-used later by the American like village, the site ends up being finally abandoned in the Sixties, the geographical conditions not being favourable with the expansion of the village. Today, the debris of the old factory is still visible: they are amoncèlent in metal heap rusted by the acid moisture of the volcano, gradually covered with time by the hot sources and concretions.

See too

Valley of the great rift

External bonds

Total Volcanism Program - Volcano Dallol
Description of Dallol by Futura Science (With natural Ushuaia)
detailed Texts and photographs of Dallol
Site with photographs of the dallol
Page with many precise photographs of the dallol
Photographs, charts and description of Dallol by activolcans

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