Geysers

This category includes natural geysers, perpetual spouters and cold water geysers of the world.

What are natural geysers?

Hasty hydrogeologist would say: geysers are thermodynamically and hydrodynamically unstable hot springs. "Normal" people would say – geysers are hot springs which at more or less regular intervals shoot up a fountain of boiling water and steam. Sometimes these fountains are even 100 m tall… or even 450 m!

A recipe for a natural geyser

Geysers are a rarity – there are just a few places in the world with true geysers. This is because there are needed four preconditions for a proper geyser:

• Constant supply of ground water. A permanent flow of groundwater is not that common on Earth – many locations are too dry for this. A continuous flow of groundwater is rare on the summits of volcanoes – locations, which otherwise would be good candidates for geysers. Sometimes not too much groundwater is needed – the climate around El Tatio geysers (Chile) is dry but geysers here are economical and reuse most of the water.
• Source of heat – magma close to the ground surface – close enough to heat the groundwater above the point of boiling. One should remember that higher up in the mountains the boiling point is at a lower temperature, f.e. in Yellowstone (2300 m above sea level) the boiling point is at 93° C.
• Suitable configuration of groundwater reservoir. Underground reservoirs of geysers are very hard to access, but research thus far shows, that reservoirs of geysers might be very complex, consisting of smaller channels and large voids.
• Tough surrounding rocks. The hydrothermal processes in the geyser create high pressure and fragile rocks quickly cause the collapse of the geyser. Even the sturdiest rocks can not last these pressures forever – due to this, the lifetime of most geysers is not very long. Most geysers of the world have formed in rhyolite – a specific volcanic rock with a similar chemical composition to granite.

How works a geyser?

When the temperature of water exceeds a boiling point, the water turns into steam which takes at least 1500 times more space than the water. If the boiling point is exceeded in the whole mass of water, an explosion happens.

Thus – after the eruption of the geyser the reservoir has been emptied. Colder water starts to fill up the reservoir – and it starts to heat up. At some moment the whole reservoir is filled with water. At the deepest part of the reservoir, the rocks are hotter and water gets heated beyond the point of boiling. The pressure of the water column above it at first does not allow for the steam to rise up.

Now the water column in the geyser is unstable – and even a single bubble or small stone leads to a sudden eruption, or the eruption starts by itself at a certain moment. The steam suddenly pulls upwards and together with the upper layers of the water flies up in the air. As the water column gets rid of the colder layers of water, the remaining steam also blows up. This continues for some time until the geyser reservoir is empty. Now it can start again…

Types of geysers

There are distinguished two kinds of natural geysers:

• Cone geysers are erupting from the summit of a small cone – they look like small volcanoes. This cone is shaped by the geyser itself and consists of geyserite – siliceous rock. Geysers in Dallol (Ethiopia) though have created cones of salt.
• Fountain geysers are beautiful pools without bottoms, filled with unusually lucid water. These pools erupt with splashing action.

What are perpetual spouters?

There are springs that permanently shoot up boiling water and steam. Here the mechanism is simpler – as the water gets into the reservoir, it is turned into steam almost instantly and is blown up in the air.

Such springs are very interesting natural landmarks – but they are not geysers. Geysers have periodic, visually very impressive explosions, perpetual spouters are permanent and not high.

Unfortunately most tourists and, what is worse – the tourism industry – calls them geysers. Wrong!

What are cold water geysers?

Water in many springs is rich with carbon dioxide. If the configuration of the spring reservoir is similar to the one of true geysers, the effect can be similar: at the depth of the spring, the reservoir has accumulated the CO₂ gas. It can not rise upwards due to the pressure of the water column above it. At some moment the pressure gets so high, that the water column above the gas is pushed upwards, like a cork from a bottle of champagne. Ola! A fountain of genuine carbonated water gets off!

Cold water geysers are man-made – these are just boreholes that have reached deep layers of carbonated water. Sometimes the upper end of the metallic borehole gets covered with sediments of lime and dissolved iron from the borehole itself – there forms a weird-looking cone in orange and brown color.

In some of these springs the water is not cold – it might be even hot. Nevertheless, they are powered by carbon dioxide and not steam.

These landmarks are partly artificial and definitely: not true geysers.

There are the following articles about the geysers: