Editer la page Suivre ce blog Administration + Créer mon blog

Earth of fire

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 .

Analavory geysers. Ampefy Itasy Madagascar - Sangitiana fli
                      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 - voyage forum
Analavory - Madagascar travel forum - colored and streaming travertine of Analavory Site - Travel Photo -Forum

Analavory - madagascar évasion                  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.

Analavory - Ecololo photoree           
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 .

Analavory geysers - Quettu
               Madagascar - Analavory : a geyser and pools - photo Quettu

The massive of Itasy was sculpted by an intense Quaternary magmatic Vulkanismus3thrust, 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.


Ngilofotsy 1432 – Betahezana 1489 – Andranonatoa 1612 -

                            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




- Wondermondo - geysers of africa - link

- Mada Tana - divers dossiers - link

- Global Volcanism Program - Ankaratra field


Articles récents

Hébergé par Overblog