Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage
We can not close the chapter over african geysers without mentioning the Analavory geysers, near Lake Itasy on the island continent of Madagascar. Unlike the African rift geysers, they have no direct link with geothermal and are termed cold water geyser .
Madagascar , one of the geysers Analavory - photo Sangitiana / Flickr
Eruption is driven by bubbles of carbon dioxide , instead of by
steam.
To Analavory , excess water from near mines of aragonite
was removed by metal pipes . The warm waters rich
in carbonic acid are readily dissolved large amounts of clay and iron from the pipelines. These sewage
emerged on the bank of the river Mazy. Decompression of CO2 bubbles
brought out the water like a champagne bottle.
Analavory - Madagascar travel forum - colored and
streaming travertine of Analavory Site - Travel Photo -Forum
Madagascar - colored travertine of Analavory Site - photo Madagascar
Escape
Cooling , silt and iron precipitated , forming mouths of travertine, where aragonite is colored in orange, yellow and rust by the metal of pipeline and by thermophiles that are developed .
The mouths of the artificial geyser grew with time , reaching over
four meters in height.
Madagascar - Analavory : the mouth of a geyser -
Ecololo / Photoree Photo
Four geysers are mentioned on this site, which pulsate their
carbonated water at 20-30 cm.
When clay blocks a time the pipeline, the water is pushed, to the breaking of the dam , more than three meters ... small in relation to references to the past that tell a height of 20-25
meters.
Located close to the
Ambohitriririnina hill where the king Andriampohy reigned, the site of Analavory takes a singular
story that has imposed a " fady ", a taboo very well respected in the region.
In this most spectacular part of these
deposits healing water, beans and goat meat are categorically prohibited. This
is because the king , before dying , had a beans and goat meat meal. Making his soul , the sovereign has forbidden
to all his descendants to eat what he thinks have led to his death, on the site of geysers.
Before becoming a touristic place, this site was used by the Malagasy who came to perform ancestral rites , the " Fanasinana " in the hope of having children , to recover health after
any disease , or to obtain a solution their daily problems.
In that time , the " mpimasy ", the traditional healers, were the only
masters of the place.
Two pools silt-laden are still popular for the virtues of the water that
flows .
Madagascar - Analavory : a geyser and pools - photo Quettu
The massive of Itasy was sculpted by an intense Quaternary magmatic thrust, and is one of Madagascar's most recent volcanic massif.
The Itasy volcanic field contains various structures :
lava domes (black on the map), cinder cones and maars .
Itasy lake , 45 km², owes its origin to a lava
flow that blocked the valley, creating a natural dam for the waters of Lily and Mazy rivers . The last
eruption occurred there is only 8,000 years .
Madagascar - location of the volcanism in the
Cretaceous (blue) and Cenozoic (red) - the massive Itasy in a circle in the center - Doc. Vulkanismus / Besarie
1964.
Madagascar - massive of Itasy - some volcanic domes :
from left to right , the dome Ngilofotsy 1432 m
- Betahezana dome 1489 m - the trachytic dome Andranonatoa 1612 m and dome Ambohitsitiaolona . - Photo MadaTana.com
Sources:
- Wondermondo - geysers of africa - link
- Mada Tana - divers dossiers - link
- Global Volcanism Program - Ankaratra field
Thème Magazine - Hébergé par Overblog