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, Herľany. 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.
