Hot spring

A hot spring is a hydrothermal source, exiting at the water, which is significantly warmer than the surrounding groundwater. According to the definitions groundwaters are referred to as thermal water in Germany when its temperature exceeds 20 ° C at the exit location.

Formation, occurrence

In general, thermal springs occur in areas with increased volcanic activity (eg, Japan, Taiwan, Iceland ) and or or in the vicinity of deep -reaching fault systems (eg Aachen, Baden- Baden) on. The water is underground heated, either by volcanic activity or by the water circulates into deeper regions of the earth and heats up there according to the geothermal gradient. The hottest springs in Europe in Bad Blumau ( deep drilling ) reached 107 ° C, Bad Radkersburg (deep hole) 80 ° C. Heat-Acute (France, natural source ) 81.5 ° C, Aachen ( natural source ) 74 ° C, in Carlsbad ( natural source ) 72 ° C and in Wiesbaden ( natural source ) 66 ° C. In volcanogenic areas, the water temperature is partially near the boiling point. Whereby always be observed that the boiling point of water depends on the altitude, the air pressure and the amount of dissolved substances (see below) and the water temperatures above are not mutually comparable sometimes. During the ascent to the surface are usually different gases, such as sulfur or carbon dioxide gases released.

The area with the largest concentration of hot springs on land, the upper Geyser Basin in Yellowstone National Park (USA). 62 % of all hot springs ( with the exception of the oceans ) are located there. The most extensive system of thermal springs exist on the ocean floor at mid-ocean ridges. Iceland as part of the mid-ocean ridge is also known for its many hot springs.

Coloring

On the immediate point of exit of hot springs are often sintered paragraphs observed that according to the chemical structure of the thermal waters from white to gray ( lime ), bright yellow, orange and brown (depending on the iron content) can be colored to black ( manganese). In addition (for example, cyanobacteria or Thermus aquaticus ) can lead to discoloration of the water or the sintering paragraphs, depending on specific water temperatures microorganisms such as algae and bacteria. The color that is caused by many of these micro-organisms varies from light yellow to dark green to orange.

Communities

Thermal springs are generally poor in species. Basically you can say that " normal" water animals and plants at temperatures above 30 ° C can not survive permanently. Thermal springs are therefore colonized by specialized communities. The limits to where specialized aquatic organisms can adapt to heat, are very different. In beetles and rotifers the outermost limit is 45-49 ° C. Blue-green algae tolerate up to 69 ° C, filamentous bacteria ( Chlamydothrix thermalis ) up to 77.5 ° C. Boiling hot springs are at the surface largely free of organisms. However, Hot springs on the ocean floor can still be colonized at much higher temperatures of bacteria, since in the high ambient pressure, the water does not boil (see below). Here are especially unique and explored more recently communities ( see black smokers ).

Hot water also contains little dissolved oxygen, whereas the high temperature greatly increased oxygen demand of most organisms. Many organisms, therefore, suffer from lack of oxygen. Some species solve this problem however, by appearing to breathe, such as water snails and water beetles.

Many thermal springs also contain dissolved hydrogen sulfide, which reacts with dissolved oxygen and thus further down is the oxygen content. For many organisms, hydrogen sulphide is toxic already beyond itself. Numerous bacteria (eg Beggiatoa arachnoid membrane Thiotrix nivea ) and some blue-green algae ( Spirulina sp., Oscillatoria chlorina ) but are capable of hydrogen sulfide not only to endure, but even to use as an energy source for their own growth. In sulfur springs such organisms usually come before masse. Some green algae such as hydrogen sulfide Cosmarium laeve can not use them, but put up with him and are therefore to be found in sulfur springs. Against this backdrop, hydrothermal vents are also discussed in connection with the origin of life on Earth.

The effluent of a thermal source, usually prevail more moderate and much more favorable conditions. The water is warm, but not hot, enriched by the movement of oxygen, and there is no seasonal temperature fluctuations. We find, therefore, in the course of thermal springs in the temperate zone sometimes species that otherwise only occur in the subtropics and tropics. In the Spa in Baden near Vienna, is true of the snail Physa acuta or the grass Cyperus longus.

Special hot springs

When geyser is a special type of hot springs in which the water is forced at regular or irregular intervals as a fountain gush up and splashes. Fumaroles are hot springs, where the water escapes in the form of steam. Is the discharge water mixed with mud and clay, it is called a mud pot.

This water mixes a thermal spring in the ground with cooler, influenced by precipitation groundwater, gives a warm source.

Almost all the hot springs in the world contain fresh water. The only three saltwater hot springs are found in Italy Vesuvius, on the Japanese island of Hokkaido and on the Taiwanese island of Lu Dao ( " Green Island ").

Sources at the bottom of the deep sea

In the deep sea there are several very lofty and volcanically active mountains. They form a erdumspannendes network, which is tens of thousands of kilometers long. On this mid-ocean ridges to find thermal springs with temperatures greater than 400 ° C. They are caused by sea water which penetrates the earth's crust and heated flows out again. This form on the seabed from precipitated minerals known as black and white smokers, tube-or cone-shaped chimneys, out of which emerges the hot water along with a sediment cloud.

Thermal springs on the sea floor can also arise through an exothermic chemical process of serpentinization, and are therefore not bound to the mid-ocean ridges. For the first time such a source was discovered in 2000 ( Lost City, with temperatures between 40 ° C and 90 ° C).

Use

Hot and warm springs are often used for therapeutic purposes, as they are rich in dissolved minerals than cold springs. In the North American Indians hot and warm springs were already known before about 10,000 years ago and, as a sanatorium use. Among the most abundant thermal springs in Germany include the Aachen thermal springs, which have led as well as other sources for the construction of baths.

Thermal springs can be used as energy sources. For geothermal energy, for example, over 50 percent of primary energy in the country is produced in Iceland.