Volcanic activity is like the breath of the planet. As long as the planet lives, it breathes, and this breath shifts tectonic plates, which leads to volcanic eruptions, geysers, the release of thermal springs and the appearance of mud pots. About the underground heat, the restless volcanoes of Europe, the geyser that gave the name to the rest of its family, fumaroles and how soap can make a geyser erupt.
Etna Volcano (Sicily, Italy), under the slope of which one of the largest cities in Sicily Catania is comfortably located, not only the largest and highest volcano in Europe, but also one of the most active on the planet. Eruptions occur both at its top and on the slopes.
Etna. Photo: Alisa Veselkova / Chrdk.
Volcanic activity at the top of Mount Etna can last for years or even decades without stopping (for example, from 1955 to 1971 or from 1995 to 2001). And eruptions on the mountainside can last from several hours to more than a year. In 1991-1993, it lasted 472 days.
View of one of the craters on the top of Mount Etna. Photo: Alisa Veselkova / Chrdk.
Just a hundred years ago, there was only one crater on the top of Etna - the Central one. But now there are four of them. These are Vorajine (Italian "abyss") and Bocca Nuova (Italian "new mouth"), formed respectively in 1945 and 1968 inside the Central Crater. Two more are the Northeast Crater - the highest point of the mountain, 3330 m, appeared in 1911, as well as the youngest and, as is typical of the young, the most active - the Southeast Crater, "born" in 1971.
One of the craters on the top of Mount Etna. Photo: Alisa Veselkova / Chrdk.
Volcanologists distinguish several types of eruptions. For example, a volcanic type named after Fr. Vulcano are short, strong, but relatively small explosions with the release of viscous magma and the release of material into the air that can reach speeds of up to 350 meters per second. In the Strombolian type (from Stromboli Island), the volcano erupts continuously for several months or years, throwing out large amounts of liquid lava, bombs and pieces of hot slag. If the eruption is characterized by a large volume of very liquid lava emerging from the crevices, then it is a Hawaiian type of eruption. And the most powerful eruptions are of the Plinian type: powerful and sudden explosions with the release of viscous lava and a column of gas and dust, the height of which can reach 50 km.
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Etna has combined several types. The eruptions of this volcano can be accompanied by explosions, lava flows, the release of gas, ash, chunks of slag and other material.
Etna craters. Photo: Alisa Veselkova / Chrdk.
Etna belongs to stratovolcanoes. These are cone-shaped mountains that can be imagined as a puff pastry: instead of dough - a layer of solidified lava, instead of cream - ash and debris that are formed during the next eruption. This is how the volcano grows, layer by layer. The vent below is connected to the magma chamber, and from above it is crowned with a crater.
Fumarola on the slope of Etna. Photo: Alisa Veselkova / Chrdk.
Fumaroles are a release of hot volcanic gas and vapor. They are different, for example in composition: sulphurous - solfatars or carbonic - mofets. And they are not only visible, but sometimes heard. Gas escaping through the holes may hiss, whistle, or even burst out of the ground with a roar. This fumarole baby in the photo above did not even hiss, but snuffled almost audibly.
Fumaroles on the slope of one of the Etna craters. Photo: Alisa Veselkova / Chrdk.
Volcanic gas is 50-85% water vapor. Over 10% is accounted for by carbon dioxide, about 5% - by sulfur dioxide, 2-5% is hydrogen chloride and 0.02-0.05% - hydrogen fluoride. Hydrogen sulphide and gaseous sulfur are usually found in small amounts. Sometimes hydrogen, methane and carbon monoxide are present, as well as a small admixture of various metals.
Fumarola in Iceland. Photo: Alisa Veselkova / Chrdk.
Most often, the proximity of fumaroles can be judged by the smell - the strong smell of rotten eggs, that is, hydrogen sulfide, which is part of the gas. Sulfur deposited on the surface gives the soil around a bright yellow color.
The top of Etna. Photo: Alisa Veselkova / Chrdk.
In 122 BC. there was an explosive eruption of Etna, during which the falling ash and lapilli - tiny pieces of porous lava - broke the roofs of many buildings in the city of Catania. But its population was exempt from taxes for 10 years!
Etna slope. Photo: Alisa Veselkova / Chrdk.
Etna is located at the junction of the African and Eurasian tectonic plates. Moreover, the first moves towards the Eurasian, plunging under it. The eruptions of Etna are connected precisely with the fact that the downward plate melts and raises the Eurasian plate.
Smoke comes out of one of Etna's craters (in the background). Photo: Alisa Veselkova / Chrdk.
Etna consists of an ancient shield volcano, on the top of which a young stratovolcano "grew". The eruptions of the shield volcano began about 500 thousand years ago, and the stratovolcano began to form about 35 thousand years ago from viscous trachytic lava.
Etna slope. Photo: Alisa Veselkova / Chrdk.
During the eruption of volcanoes, gas, ash and various materials are released - from miniature lapilli to volcanic bombs, lumps of lava stuck together. And from mixing lava with sand and ash, porous volcanic tuff can be obtained. Its color can be any: black, brown, brown, red, orange, yellow, pink, or even purple and bluish-white.
One of the craters of Etna. Photo: Alisa Veselkova / Chrdk.
Ash clouds from the Etna eruption are especially dangerous for aircraft. Once in the engine, ash particles can melt and cover moving parts with a layer of glass, which can lead to engine failure. Such clouds are often visible from space and pose serious problems for airlines flying to Catania, which is only a couple of tens of kilometers from the volcano.
Sheep on the slope of Mount Etna. Photo: Alisa Veselkova / Chrdk.
Volcanic soils, or andosols, are formed from volcanic eruptions and are quite fertile: they are rich in nitrogen, phosphorus and sulfur. At the same time, the volcanic glass contained in them is easily weathered.
Milos Island (Greece). Photo: Alisa Veselkova / Chrdk.
The Greek island of Milos, on which a statue of Venus was found at the beginning of the 19th century (and, in fact, therefore, received the name of Milos), is located on the South Aegean volcanic arc. The island was formed by the eruption of several volcanoes, it has an active stratovolcano and many fumaroles. There are geothermal springs in and near Milos, the temperature of which reaches 300 degrees.
Thermal spring in Nepal. Photo: Alisa Veselkova / Chrdk.
Thermal waters are underground waters with a temperature of 20 ° C or more. They are often found in areas of active volcanism. The depth of occurrence of thermal groundwater depends on the climatic zone: in areas of permafrost development, it is 1500-2000 m, in the subtropics - up to 100 m, and in the tropics these waters often come to the surface.
Children at a warm spring in the village of Tatopani (Nepal). Photo: Alisa Veselkova / Chrdk.
“ Tatopani ” is translated from Nepali - “warm water”. In poor mountain villages, such springs significantly make life easier for people: it is easier to wash and wash the dishes in them, and wash yourself.
Crater Lake Kerid (Iceland). Photo: Alisa Veselkova / Chrdk.
Crater Lake Kerid is located in the south of Iceland in the western volcanic zone. The crater is about 3 thousand years old, and by volcanic standards it is quite young, thanks to which it managed to maintain an almost perfect shape.
There is no single version about the origin of Kerid. According to one of them, Kerid was once a cinder cone - a small conical volcano, but it exhausted its entire source of the volcano and sank under its own weight into the resulting cavity.
Small geyser in Iceland. Photo: Alisa Veselkova / Chrdk.
Iceland is crossed from south to north by the Mid-Atlantic Ridge. This is the border of the divergence of the North American and Eurasian tectonic plates in the North Atlantic and the African and South American plates in the South. This is partly due to the high volcanic activity on the island. There are more than a hundred "mountains of Fire" in Iceland. These are crater rows, thyroid, stratovolcanoes, mud, underwater and more.
Geyser Strokkur in Iceland. Photo: Alisa Veselkova / Chrdk.
Geysers (Italian geysa - "break through", "rush") are hot springs that occur where there is volcanic activity. The inhabitants of the island are lucky: there are many geysers in Iceland, but they are quite rare in the world. This is mainly due to natural reasons, because geysers almost "live on a volcano": earthquakes often occur in these places, mudflows and avalanches descend, as a result of which geysers fall asleep or they lose their power source. This happens quite often in Kamchatka in the legendary Valley of Geysers. In 2007, there was a landslide, and in 2014 a mudflow came down. Both events greatly changed the operating mode of many geysers.
Geyser Strokkur in Iceland. Photo: Alisa Veselkova / Chrdk.
The Høykadalur Valley in the south of Iceland is a real geyser klondike. The Strokkur geyser erupts every five to ten minutes, but the column of water and steam does not rise above 20 meters. And a few tens of meters away is Geysir, whose name, in fact, has become a household name.
Geysir has been active for about 10 thousand years, although during this time it has had ups and downs. In 1845, it erupted 170 meters, and after just a year - only 54. At the end of the 19th century, Geysir saved up his strength and released a column of water and steam 60 meters several times a day, and in 1916 he almost fell asleep. After 20 years, a channel was dug around it through a layer of quartz, thanks to which the water table dropped and the geyser became more active. As soon as the channel was clogged with quartz, the eruptions stopped. In the 1990s, the geyser was artificially stimulated to erupt with soap (I will tell you how this is done later). But this was bad for the environment, so this method was quickly dropped. But after the earthquake in 2000, Geysir "came to life" again and for two days in a row spewed a column of water and steam to a height of 122 meters. The last time he woke up was in February 2016, and now he is considered almost asleep.
Strokkur at rest. Photo: Alisa Veselkova / Chrdk.
The geyser erupts because the water in the underground voids is heated by volcanic heat, turns into steam, and the pressure of the steam raises the water upward. However, it turned out that the geyser can be made to erupt even when it was not going to. Just add (lots of) soap.
Surfactants (which include soaps and detergents) have surface-active properties, that is, they reduce surface tension. Water molecules disperse more easily, and the liquid turns into vapor, which rushes upward and carries water with it.
This method of artificially making a geyser work was discovered in New Zealand in 1901 by pure chance. At this time, an "open prison" was set up on the North Island in the town of Wai-O-Tapu - a kind of settlement for criminals who were considered harmless to society. But, among other things, Wai-O-Tapu is an area with high geothermal activity. The prisoners who settled there ran a household and, of course, began to wash their clothes right in these hot springs. One day, after washing, one of them poured a fairly concentrated soap solution, it seeped through cracks in the rock and started a reaction in an underground reservoir, the water from which burst out.
By the way, the Lady Knox geyser in Wai-O-Tapu is still being launched in this way, but the soap was replaced by detergents that are considered less harmful to the environment.
Volcano Hekla (Iceland). Photo: Alisa Veselkova / Chrdk.
Iceland's most famous and infamous volcano, Hekla, is a fairly active volcano. It is about 6-7 thousand years old, and since the beginning of the second millennium AD, about 20 large eruptions and the same number of small ones have occurred. The first written evidence of the eruption of Hekla dates back to 1104. In general, from the 13th to the 20th century, Hekla was very active and erupted once or twice in a century. In 1300, the eruption lasted a whole year. But since the end of the last century, the volcano has become calmer.
Mud boiler in Iceland. Photo: Alisa Veselkova / Chrdk.
Several mud pots can be seen at the Hverir geothermal field in Iceland. Sulfur colors the field in various shades of yellow and orange, but you want to shut your nose - the corresponding aroma hovers over the field.
A mud pot is usually filled with thick, gurgling clay. Pouring over the edges of the cauldron and cooling, the clay can gradually form the walls, and you get a small mud volcano. However, it has little in common with a real mud volcano.
Fumarola at the Hverir geothermal field. Photo: Alisa Veselkova / Chrdk.
Khverir belongs to the Krabla volcanic system. Everything on the field smokes and gurgles. Steam seems to be coming from every crack. Some of them were made by man: in the 1950s, several holes were drilled here to study sulfur - this is how "artificial" fumaroles were obtained.
Mud boilers in Hverir. Photo: Alisa Veselkova / Chrdk.
A mud boiler is essentially a double boiler. Surface water is collected in a shallow reservoir, the tightness of which is ensured by a layer of clay. From below it is heated by thermal waters, and the dirt in the boiler begins to bubble.
Mud pots are sometimes compared to a palette for paint - so varied are the colored spots surrounding them. For example, iron oxide colors reddish, pink, beige.
Mud volcano near Kerch (Russia). Photo: Alisa Veselkova / Chrdk.
Mud volcanoes erupt with mud mixed with gas and usually water and sometimes oil.
They, like mud boilers, can be found in Russia. A couple of mud volcanoes and two mud pots are active a few kilometers from the village of Vulkanovka in Crimea. The height of the volcano in the photo is no more than four meters higher.
View of the valley with mud boilers in the Crimea. Photo: Alisa Veselkova / Chrdk.
The largest mud volcano in Crimea is Dzhau-Tepe, whose height reaches 60 meters. He was active at the beginning of the 20th century, but has been dormant for the last decades.
Geyser lake near the village of Aktash in Altai (Russia). Photo: Alisa Veselkova / Chrdk.
Thermal springs can create such an unusual lake. Jets of water raise blue silt from the bottom, giving the reservoir an unusual color.
Alisa Veselkova