Translations of Encyclopedia about Geology

Volcanic Phenomena

During the advanced stages of eruption, quite often there is no lava outflow, only escaping gases and steam. These processes are called volcanic exhalations.

Underground water, which is heated by magma, penetrates to the surface in the form of hot springs or geysers. Geysers are boiling hot springs that expel at intervals great volume of water. This activity is accompanied by low underground rumbling.

One of the most famous geysers is the Old Faithful in Yellowstone National Park, USA. Other great geysers are in New Zealand and Iceland. In Iceland, the energy produced by geysers is utilized in steam-powered electric plants. Hot water continues to shoot up for decades following major volcanic activity. This hot water from hot spring geysers contains certain amounts of valuable minerals.

The so-called fumaroles are another volcanic phenomenon. They are volcanic exhalations of gases, which contain mostly steam. Additional integrating parts of the fumaroles are gaseous matters escaping at temperatures between 800 and 200 degrees Celsius. A major part of these consists of iron compounds, lending to the fumaroles colourful appearance.

Steam and sulphuric compounds rise from the so-called solfataras (called after the volcanic crater Solfatara near Naples, from which steam and hydrogen sulphide are still escaping) at temperatures of 250 to 100[sic] degrees Celsius. Since antiquity, hot springs have been considered to have medicinal effects. During the Roman times people would take steam and mud baths as treatment of respiratory ailments and fatigue.

Sulphur is produced by oxidation of hydrogen sulphide. It settles in the thick yellow crust around the vents from which hydrogen sulphide is escaping. This phenomenon often creates economically viable sulphur deposits.

Exhalation of carbon dioxide takes place at temperatures below 100 degrees Celsius. This exhalation is called mudpot. We find this phenomenon not only in regions of volcanic activity, but also in regions where there are extinct volcanoes. In Germany, we find mudpots in the region called Swabian Jura (in the river-basin of upper Danube).

Very dangerous volcanic phenomena are the landslides and mudslides, which are the combination of water and volcanic materials, and which are called lahar. They are the result of the melting of glaciers due to lava flow, or when it rains heavily shortly after a volcanic eruption, the freshly accumulated ash will turn into mud. Lahars move enormous amounts of material and can bury entire towns. This is what happened in Colombia. In 1985, when the volcano Nevado del Ruiz erupted, lahars resulting from the melting glacier buried in a very short time the town of Armero. Some 25.000 people lost their lives in that disaster.

Translating Spanish Hungarian Translations Hungarian Spanish Translating Norwegian Italian Translations Italian Norwegian Translating Czech