We cannot close the chapter on African geysers without mentioning the Analavory geysers. It is near Lake Itasy on the island continent of Madagascar. The Cold Geysers of Madagascar are distinct African rift geysers; they have no direct link with geothermal and are termed cold-water geysers. There are four unusual geysers almost twelve kilometers northeast of the town of Analavory.
Surprisingly, there is no volcanic activity observed underneath Analavory that superheats underground water and forces it up as steam. The warm water gushing out from the mouth of these limestone mounds is not hot. The unusual cold geysers are situated in an area near some aragonite mines. The Analavory geysers aren’t natural at all, as excess water from the mines is removed by metal pipes that terminate at the bank of the Mazy River.
The cold geyser water is rich with carbonic acid, which can easily dissolve large amounts of lime along the way. Moreover, 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 causes the dissolved carbon dioxide gas to erupt in bubbles, fabricating a geyser like a phenomenon.
This is akin to opening an aggravated bottle of soda. But over time, the dissolved lime and iron precipitate 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 continue to grow.
Most of the time, the carbonated water spouts 20–30 cm, but occasionally, when the vents are blocked by the precipitated lime, the obvious buildup of pressure produces a spouting to numerous meters once uncovered. Cold geysers such as those at Analavory are often called cold water geysers, and there are only a handful of naturally 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, Herany.
A geyser very akin 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, recuperating health after any disease, or getting a solution to their daily problems. At that time, the “mpimasy”, the traditional healers, were the only masters of the place.