Mofetta

A is the exit point mofette of carbon dioxide ( CO2) at temperatures below 100 ° C. It is thus a subspecies of fumarole and is considered to be a side effect of volcanism.

The name mofette derives from the Italian word mofeta, which comes from the Latin mefitis or mephitis. It means " harmful perspiration ".

Besides carbon dioxide can mofettes also contain methane and hydrogen sulfide, trace helium and other noble gases. You can change the surrounding rock to chemical interference. Hydrogen sulfide Shares may lead to a smell of rotten eggs.

Appearance

Mofettes may have different outer appearances depending on the surrounding soil and the water outlet from the source. The spectrum ranges from dry gas wells up to kohlenstoffdioxidhaltigen mineral springs. Relatively dry mofettes with little or no water outlet can look very similar especially after rainfall mud pots, they are frequently referred to erroneously as a small mud volcanoes.

If mofettes drilled and cased (ie, a stable channel is built h ), it can be formed under certain conditions, a cold water geyser. However Kaltwassergeysire are usually at least partially human structures.

Plants die at a Mofettenstandort or are significantly inhibited in growth. Often the floor is free of any vegetation. In Central Europe, only a few plants tolerate the location. These include marsh plants such as reeds, which adapt to the oxygen- poor soils. The marsh sedge grows in a Mofettengebiet only in areas with extremely high gas concentration.

Animals are found mostly dead or dying in Mofettengebieten. Frequently die in other animals, imagine the secure prey in the animal carcasses and reside in the mofette. It was observed that the mound and associated underground tunnels of moles at the external borders of mofette end, where the carbon dioxide concentration is still low enough.

Hazards

The light emerging from mofettes carbon dioxide can accumulate in depressions and displace the air. Especially in the morning it comes to high concentrations near the ground. When the sun has warmed especially the carbon dioxide (higher absorption), it rises and the concentration drops rapidly (example: the Bossoleto source in Tuscany ). In certain landforms, in which the gas can not flow so fast, a mofette a danger to humans and animals can be. Living things die after a short period of oxygen deficiency or by the acidification of the blood. Near mofettes therefore often find for a long time without decomposition permanent animal carcasses.

A in this context has become known mofette is the dog grotto at Agnano in the Phlegraean Fields ( Campi Flegrei Italian ) west of Naples. It is so named because the escaping carbon dioxide because of its high specific gravity accumulates in this deep cave there and into guessed animals suffocated, as has been observed in dogs.

Occurrence

Known mofettes in Germany are in the Laacher See volcano in the Eifel and in the mist cave in Bad Pyrmont and the upper Neckar Eyach that are now accessible by drilling. In the Eifel there are in addition numerous mofettes the Kaltwassergeysire Geysir Andernach and Wallender Born.

Mofettes occur further on, inter alia, in today's Saxon- Bavarian- Bohemian border country (eg nature reserve Soos in West Bohemia).

The relationship between the isotope helium -3 and helium -4 is regarded as an indication of the depth of origin of the gases mofette. Changes in the isotope ratio, (Bohemia ) are measured as described for example in the Bublák - mofette diligence on Bach in the Cheb basin, as an indicator for the geological volcanism related activities. The temporal relationship between their typical earthquake swarm and the helium isotope ratio is currently under investigation by the Centre for Environmental Research Leipzig-Halle and the GFZ Potsdam. Furthermore, it is known that ground-level magma chambers fill, among other things Etna up to six months before an eruption with carbon dioxide. The gas dissolves poorly in the magmas and hospitable to the surface. The increased Mofettentätigkeit and the increased concentration of carbon dioxide impending volcanic activity can be detected.

Mofettes comes geysers similar to a certain importance in earthquake research. So is often observed that changing gas composition and outlet volumes while smaller foreshocks from resulting cracks and fissures in the rock and so announce major earthquake activity.

More active mofettes you can also in Greece on the Methana ( whose name probably from the gases comes = μεθάνιο αέριο - methane ( a) gas), on the island of Milos, the island of Santorini and especially in hydrothermal crater Stefanos visit on Nisyros.

Use

The effluent from mofettes carbon dioxide dissolved in water is mainly used as carbonic acid in mineral waters and other Erfischungsgetränken. The mineral-rich waters of the Eifel, the carbon dioxide is due to the volcanic activity, are sold worldwide. At the end of the 18th century was drilled to carbonic acid in 500 meters depth. A patent Raydt in 1880, it was possible to liquefy the carbon dioxide recovered, and to facilitate the storage and transport it.

To win carbon dioxide, the effluent gas from boreholes dry mofettes was initially collected with metallic hemispherical domes and using extracted by pumps. Meanwhile, water is pressed against the ascending gas in drilling. The water is sufficiently enriched with carbon dioxide, it is recovered in a separating process on the surface.

Under control conditions are mofettes in Balneology, ie in the form of medicinal gases used. Source gas therapies are mainly offered in Romania, but also in the German Staatsbad Pyrmont. The mofettes be edged, remodels and set of steps. Under medical supervision accept patients according to the severity of the disease at different levels of space. Low concentrations of carbon dioxide stimulate circulation and improve blood circulation.

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