Page 72 - Volcano and Geothermal Tourism

Volcano Tourism in Ethiopia and the Danakil Rift Zone 49

Figure 3.3 The raised level of the lava lake of Erta Ale in February 2009
Source: Photo courtesy of Hans-Jürgen Knoblauch

potash deposits are found near the surface. These Locals also tell stories of the existence of mine
are the result of upward transport of salts dissolved shafts dug into Dallol Mountain, probably in the
in geothermally heated groundwater from deep 1930s, when the Italian company Compagnia
primary deposits. Secondary deposits form near Mineraria Coloniale was active in the area.
the surface as the water that transported them However, no evidence for underground mining
evaporates. They include significant bodies of activities can be found today and it seems
potash in the form of sylvite (KCl), carnallite questionable whether mine shafts would have
(MgCl -KCl-6H O) and kainite (MgSO -KCl- been driven into an active geothermal area.
4
2
2
11/4H 0) salts. The main sylvite-bearing zones are Certainly, in the 1960s, the US Parsons
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between 15 and 40m in thickness (Hardie, 1991). Company drove exploratory mine shafts down to
In 1906, the Italian T. Pastori recognized the ‘Musley’ sylvite strata west of Dallol at the base
surface deposits of carnallite by the Black of the highlands. However, this site was many
Mountains adjacent to the Dallol Mountain. Due kilometres from the geothermal areas at Dallol
to the economic value of potash, for example, in Mountain. It is important to note that the
the fertilizer industry, this discovery resulted in terminology Dallol is often used to define a large
several mining attempts at Dallol mound and in surrounding area, which may cause confusion as
the surrounding area, remnants of which can still to the exact location of historical mining
be seen today (Holwerda and Hutchinson, 1968). operations. The primary (i.e. sedimentary) potash
It was once estimated that a spring in the Black deposits in the salt plains surrounding Dallol
Mountain area was bringing around 1000 tonnes mound are usually overlain with other evaporites,
of potash to the surface in a single year and this largely consisting of alternating layers of halite and
was initially harvested by evaporation in salt pans. mud to a depth of several metres. This crust results

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