Saturday, 29 March 2014

Cold Geysers of Madagascar

We cannot close the chapter of African Geysers without mentioning the Analavory geysers, nearby Lake Itasy on the island continent of Madagascar. Distinct the African rift geysers, they have no direct link with geothermal and are termed cold water geyser. Actually there’re four unusual geysers almost twelve kilometers north-east from the town of Analavory. Surprisingly, there’s no volcanic activity observed underneath of Analavory that superheats underground water and forces them up as steam. The warm water gushing out from the mouth of these limestone mounds which is not hot in fact.  The unusual Geysers are situated in an area nearby to some aragonite mines. The Analavory geysers aren’t natural at all, as excess water from the mines are removed by metal pipes that terminate at the bank of Mazy River.
The water is rich with carbonic acid which can be easily dissolves large amounts of lime along its way. Moreover the warm water goes through iron pipelines and carbonic acid dissolves iron as well. The carbon dioxide rich water rushes along the pipe under pressure and it emerges at the end of the pipeline, the abrupt decrease in pressure reasons the dissolved carbon dioxide gas to erupt in bubbles fabricating a geyser like phenomenon. This is akin to opening an aggravated bottle of soda. But over the time; the dissolved lime and iron precipitates into big mounds of travertine, a type of limestone, around the mouth of the outlet. The rusty orange color comes from the iron. The mounds are more than 4 meters high and will last to grow.
For most time the carbonated water spouts 20-30 cm, but occasionally when the vents are blocked by the precipitated lime, the obviously buildup of pressure produces spouting to numerous meters once uncovered. Geysers such as those at Analavory are often called cold water geysers, and there’re only a handful of natural cold water geysers on earth. The best recognized examples are Crystal Geyser, in Utah, the Wallender Born and Andernach Geyser in Germany, and one in Slovakia, Her─żany. A geyser very akin to in appearance to Analavory Geyser is the Fly Geyser in Nevada, which is an artificial geyser. Before becoming a tourist place, this lovely site was used by the Malagasy who came to perform ancestral rites, the "Fanasinana" in the hope of having children, to recuperate health after any disease, or to get a solution from their daily problems. In that time, the "mpimasy", the traditional healers, were the only masters of the place.