Acid Lake

A acid lake is a volcanic Lac of origin of acid composition and often heat being in a crater of a Volcan in activity. Often blue algas (Cyanobactérie S) color acid water of this lake in turquoise blue. This type of demonstration is found as much in the craters of volcanos effusive standard as explosive. The acid lake knows a very strong sulphuric concentration of Acid.

Origin

the acid lakes are not formed same manner as the Maar S. the acid lakes are formed in the following way:

The acid lake is formed with the or ponding of Pluie S Neige in the Cratère. Water is contaminated by pollutant gases emanating from the Fumerolle S and hot sources which percolent the bottom of the crater, which makes the lake acid and hot with a high content of Soufre.

The acid lakes are extremely rare phenomena. More the share of time, the bottom of the volcanic craters are too porous to let water stagnate inside this one. But when the edges of the volcano are rich in argillaceous matter (Old volcanic materials broken up by the acid of the fumerolles), this same “Argile” bottom because of the heat of the surrounding fumerolles and is found at the bottom of the crater. This one stops the holes and the cracks of the Solfatare S, allowing rainwater to engulf itself in the volcano. But the fumerolles, always active, can bore the layer of clay easily and make go up gas and sulfur bubbles which make acid stagnant water. Being connected to no Running nor with any Brook, water remains in the crater and continuous to be acidified, sometimes until reaching a pH lower than 0.

This phenomenon little to be formed in all the types of volcanos, although the acid lakes go more tendency to be formed in craters rich in pozzolanas, lapillis or ashes, which break up better than the basaltic stones.

There exist acid cases of lakes which lost their strong acidity after the stop of activity of the volcano. It is the case for example famous volcano Pinatubo: after the terrible explosive eruption of this one, in 1991, the crater of the volcano was filled by a lake of the crater, after strong precipitations. Then very hot and very acid, this lake lost its corrosivity gradually with the passing of years, until becoming today a lake of acidity and normal temperature.

Geology

This kind of volcanic lake is mainly made up of Eau enriched by Acid sulphuric, but of other acids, like the chloridric Acide, is included/understood there. Consequently, the water of these lakes is very Acide (going pH of 4 with less than 1) and often very hot (of 30° with 85°). The lake of the crater has an almost null activity, except rare gas increase in the chimney which connects the lake to the magmatic Chambre and of the wavelets due to the current. The absence of mobile living beings in the lake makes it quasi-stagnant. Only the Cyanobactéries (blue algas) can survive and reproduce in this medium. An acid lake can be accompanied by Solfatare S, Fumerolle S in activity, generally in the neighborhoods of this one. A volcano, without activity, even equipped with a Lake of crater, cannot have acid lake. More the lake is hot and acid, more the activity of the volcano increases. A very great activity can involve an eruption. In addition, that can cause the evaporation of the lake. The consequences can be disastrous: Repercussions of acid water rains and ashes can fall down to kilometers with the round, being able to damage dwellings and cultures, as it was the case with the Karthala in 2005.

Geography

The acid lakes are in almost all the active volcanic craters and the Caldeira S in the world:

One finds some in great quantity in the volcanos of Central America, of which Poás and Irazú.
Certain volcanos of the valley of large the rift, have some.
Much of volcanos of the belt of Fire: Kamtchatka, Java (Ijen) has some.
Of the very active volcanos in Iceland has some too.

The acid lakes are not eternal: after an eruption, an acid lake little to vaporize and leave place a basaltic pit of lava: it was the case for the Volcan shield Karthala, volcanic crater giant of the islands the Comoros: this vast volcanic crater had been filled a long time by an acid lake: after an important eruption, on April 18th, 2005, this volcano became today an enormous well of basaltic lava in fusion comparable with the Erta Ale.

The acid lakes generally have a lifespan going from some month to more than one ten year. Only the acid lakes largest, like those of Kawah Ijen or Voui, can last beyond these dates.

Color

The color of the lake is function of the Acidité, of the content of mineral components and concentration in Blue algas:

If the lake is blue turquoise, that is with the colonized blue algas aillant acid water. The higher the concentration is, the more blue is constant: a gray acid lake is thus less rich in bacteria.
If the lake is green, it is not only due to the cyanobacteries, but also to acidity: a greener water has a concentration more raised in Acid sulphuric.
If the lake is brown, it is because minerals and sediments flow in great quantity on the surface by masking the color of the bacteria.

Caution! Certain hot sources are of color light blue, not because of the presence of thermophilous organizations, as in the acid lakes, but because Silice remains in suspension in water, reflecting this bluish color.

Acid lakes to know

Poás : the most acid lake of the world (Ph=0)
Ijen, more the acid big lake of the world (More than one kilometer diameter) the second most acid lake of world (PH=0,2 approximately) after Poas, and the acid lake with the greatest sulfur concentration in the world (10 tons of sulfur rejected per day on the banks of the lake, is more than 3640 tons of sulfur per annum).
the lake Ambae, also called Voui crater, on the island of Aoba, in Vanuatu: the second plus acid big lake of the world. (Ph=2)

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