Volcanic eruptions are among the most. Types of volcanic eruptions

Volcano(from lat. vulcanus - fire, flame), a geological formation that occurs above channels and cracks in the earth's crust, through which lava, ash, hot gases, water vapor and rock fragments are erupted onto the earth's surface.

Volcanoes are divided according to on the degree of volcanic activity active, dormant, extinct. An active volcano is considered to be a volcano that erupted during a historical period of time or in the Holocene. The concept of active is quite inaccurate, since a volcano with active fumaroles is classified by some scientists as active, and by others as extinct. Dormant volcanoes are considered to be inactive volcanoes where eruptions are possible, and extinct volcanoes are considered to be those where they are unlikely.

However, there is no consensus among volcanologists on how to define an active volcano. The period of volcanic activity can last from several months to several million years. Many volcanoes exhibited volcanic activity tens of thousands of years ago, but are not considered active today.

By shape differentiate central, erupting from the central outlet, and cracked (linear), the apparatus of which looks like gaping cracks or a series of small cones.

By structural features and types of eruption distinguish:

· Shield volcanoes are formed as a result of repeated ejections of liquid lava. This shape is characteristic of volcanoes that erupt low-viscosity basaltic lava: it flows from both the central crater and the slopes of the volcano. Lava spreads evenly over many kilometers. Like, for example, on the Mauna Loa volcano in the Hawaiian Islands, where it flows directly into the ocean.

· Slag cones eject from their vent only such loose substances as stones and ash: the largest fragments accumulate in layers around the crater. Because of this, the volcano becomes higher with each eruption. Light particles fly away over a longer distance, which makes the slopes gentle.

· Stratovolcanoes, or “layered volcanoes,” periodically erupt lava and pyroclastic matter - a mixture of hot gas, ash and hot rocks. Therefore, deposits on their cone alternate. On the slopes of stratovolcanoes, ribbed corridors of solidified lava are formed, which serve as support for the volcano.

· Dome volcanoes are formed when granitic, viscous magma rises above the rim of a volcano's crater and only a small amount seeps out, flowing down the slopes. Magma clogs the volcano's crater, like a cork, which the gases accumulated under the dome literally knock out of the crater.

Main parts of the volcanic apparatus: magma chamber(in the earth's crust or upper mantle); vent- an outlet channel through which magma rises to the surface; cone- a rise on the surface of the Earth from the products of volcanic ejection; crater- a depression on the surface of a volcano cone.

After eruptions, when the activity of the volcano either stops forever, or it “dormants” for thousands of years, processes associated with the cooling of the magma chamber and called post-volcanic. These include fumaroles, thermal baths, and geysers.

Fumarole- cracks and holes located in craters, on slopes and at the foot of volcanoes and serving as sources of hot gases. In any volcanic gases, water vapor predominates, accounting for 95–98%. The second place after water vapor in the composition of volcanic gases is carbon dioxide (CO 2); followed by gases containing sulfur (S, SO 2, SO 3), hydrogen chloride (HCl) and other less common gases such as hydrogen fluoride (HF), ammonia (NH 3), carbon monoxide (CO), etc. In Cameroon (Central Africa) there is a volcano. Nyos, in the crater of which there is a lake. On August 21, 1986, residents of villages in the surrounding area heard a sound resembling a loud bang. After some time, a gas cloud that escaped from the water of the crater lake and covered an area of ​​about 25 km 2 caused the death of more than 1,700 people. The deadly gas turned out to be carbon dioxide released into the atmosphere from a not yet extinct volcano.

Baths- hot springs, widespread in areas of volcanism. Waters can be sodium chloride, acidic sulfate chloride, acidic sulfate, sodium and calcium bicarbonate and others. Often thermal waters contain a lot of radioactive substances, in particular radon. Not all thermal baths are associated with volcanoes, since temperatures increase with depth, and in areas with a high geothermal gradient, circulating atmospheric water is heated to high temperatures.

Geyser- a source that periodically releases fountains of hot water and steam. The water emitted by the geyser is relatively clean and slightly mineralized. The activity of the geyser is characterized by periodic repetition of dormancy, filling the basin with water, gushing of a steam-water mixture and intense emissions of steam, gradually giving way to their quiet release, cessation of steam release and the onset of the resting stage. There are regular and irregular geysers. In the former, the duration of the cycle as a whole and its individual stages is almost constant, in the latter it is variable, in different geysers the duration of individual stages is measured in minutes and tens of minutes, the resting stage lasts from several minutes to several hours or days.

Volcanoes cause enormous damage, especially when the eruption occurs suddenly and there is no time to warn and evacuate the population. Hot lava destroys everything that comes in its path, causing fires, poisonous gases spread over long distances, and ash covers vast areas.

Volcanic eruptions, due to their consequences, are dangerous for people living close to active volcanoes. Some of the most dangerous phenomena include lava flows, tephra falls, volcanic mud flows, volcanic floods, scorching volcanic clouds and volcanic gases.

Lava flows consist of lava - molten rocks heated to a temperature of 900–1000 ° C. Depending on the composition of the rocks, lava can be liquid or viscous. When a volcano erupts, lava flows from cracks in the volcano's slope, or overflows the edge of the volcano's crater and flows down to its foot. The more powerful the lava flow itself, the greater the slope of the volcano cone and the thinner the lava, the faster the lava flow moves. The speed range of lava flows is quite wide: from a few centimeters per hour to several tens of kilometers per hour. In some cases, the speed of lava flows can reach 100 km/h. Most often, the speed does not exceed 1 km/h. Lava flows at deadly temperatures pose a danger only when populated areas are in their path. However, even in this case, there is still time to evacuate the population and carry out protective measures.

Tephra consists of fragments of solidified lava, older subsurface rocks, and fragmented volcanic material that forms the volcanic cone. Tephra is formed during the volcanic explosion that accompanies a volcanic eruption. The largest fragments of tephra are called volcanic bombs, somewhat smaller ones are called lapillas, even smaller ones are called volcanic sand, and the smallest ones are called ash. Volcanic bombs fly several kilometers from the crater. Lapilla and volcanic sand can spread for tens of kilometers, and ash in the high layers of the atmosphere can circle the globe several times. The volume of tephra during some volcanic eruptions significantly exceeds the volume of lava; sometimes tephra emissions amount to tens of cubic kilometers. The fall of tephra leads to the destruction of animals, plants, and possible death of people. The likelihood of tephra falling on a populated area largely depends on the direction of the wind. Thick layers of ash on the slopes of the volcano are in an unstable position. When new portions of ash fall on them, they slide down the slope of the volcano. In some cases, the ash becomes saturated with water, resulting in the formation of volcanic mud flows. The speed of mud flows can reach several tens of kilometers per hour. Such flows have significant density and can entrain large blocks during their movement, which increases their danger. Due to the high speed of movement of mud flows, it is difficult to carry out rescue operations and evacuate the population.

When glaciers melt during volcanic eruptions, huge amounts of water can immediately form, leading to volcanic floods. It is difficult to calculate exactly how much water the glacier released, although it is important for planning measures to protect against volcanic flooding. This is because glaciers have many internal cavities filled with water, which is added to the water produced when glaciers melt during a volcanic eruption.

A scorching volcanic cloud is a mixture of hot gases and tephra. The damaging effect of a scorching cloud is due to the shock wave formed when it occurs (wind at the edges of the cloud), spreading at a speed of up to 40 km/h, and a wave of heat (temperature up to 1000°C). In addition, the cloud itself can move at high speed (90–200 km/h).

Volcanic gases are a mixture of sulfur dioxide and sulfur oxides, hydrogen sulfide, hydrochloric and hydrofluoric acids in a gaseous state, as well as carbon dioxide and carbon monoxide in high concentrations, which are deadly to humans. The release of gases can continue for tens of millions of years even after the volcano has stopped spewing lava and ash. Sharp climate fluctuations are caused by changes in the thermophysical properties of the atmosphere due to its pollution by volcanic gases and aerosols. During the largest eruptions, volcanic emissions spread in the atmosphere over the entire planet. The admixture of carbon dioxide and silicate particles can create a greenhouse effect leading to warming of the earth's surface; Most aerosols in the atmosphere lead to cooling. The specific effect of an eruption depends on the chemical composition, the amount of material ejected, and the location of its source.

Tsunamis often occur during eruptions of island and underwater volcanoes. In addition, clouds of flaming gases and steam formed during underwater eruptions can cause the death of sea vessels. Gas can be released not only at the points of the eruption, but also in large areas of the seabed adjacent to it, covered with sediments with a high content of gas hydrates. The latter can disintegrate into water and gas with fairly small changes in pressure, temperature, and chemical composition of the overlying water column.

16/04/2010

Experts warn that an ash cloud from the Icelandic volcano Eyjafjaldajökull will reach St. Petersburg in the evening. The townspeople's chances of watching the show are slim - it's located too high. But the consequences of the eruption greatly affected air traffic in the countries of Northern Europe. The cancellation of flights to Europe began in St. Petersburg.

1. Vesuvius, Italy, August 24, 79
The eruption destroyed the ancient Roman cities of Pompeii, Herculaneum and Stabiae. Ashes from Vesuvius reached Egypt and Syria.
Contrary to popular belief, most of the inhabitants of Pompeii left the city before the disaster; out of 20 thousand inhabitants, 2 thousand died in the buildings and on the streets. Among the dead was the scientist Pliny the Elder, who, out of scientific interest, approached the volcano on a ship and found himself at the epicenter of the disaster.
In total, more than 80 eruptions of Vesuvius are known, the last one occurring in 1944. Vesuvius is the only active volcano in continental Europe.

2. Tambora, Sumbawa Island, Indonesia, April 5-7, 1815
The largest eruption in modern history in terms of the number of human casualties (92 thousand people died during the disaster and the subsequent famine) and the impact on the Earth’s climate (ash clouds did not allow the sun’s rays to pass through, which led to a drop in temperature). As a result, the Tambora culture, which Europeans became acquainted with just a few years before its destruction, was completely destroyed.

3. Taupo, New Zealand, about 27 thousand years ago
According to geologists, the last eruption larger than Tambora was a volcanic eruption in New Zealand that led to the formation of Lake Taupo. Today the lake is one of the most beautiful and popular tourist destinations.

4. Krakatoa, between the islands of Java and Sumatra, Indonesia, August 27, 1883
The largest volcanic explosion in modern history. The tsunami it caused washed away 163 villages (killing 36,380 people). The roar from the explosion was heard over 8% of the Earth's territory, pieces of lava were thrown into the air to a height of 55 km, and volcanic ash blown by the wind 10 days later fell 5330 km from the eruption site (the approximate distance between Reykjavik and Karaganda).

5. Santorini, Greece, around 1450 BC. e.
A volcanic eruption on the island of Thera led to the death of the Cretan civilization: volcanic sulfur covered all fields and put an end to agriculture.
There is a version that the island of Thera is the Atlantis described by Plato. There is another version: the pillar of fire that Moses saw is the eruption of Santorini, and the parting of the sea is a consequence of the immersion of the island of Thera in water.
In 1886 (already AD), the eruptions of Santorini continued for a whole year, pieces of lava flying out of the sea rose up to 500 meters. As a result, several new islands appeared.

6. Etna, Sicily, Italy, 1928
About 200 eruptions of Mount Etna are known, including quite powerful ones: the eruption of 1169 led to the death of 15 thousand people. Etna is an active volcano; approximately once every 150 years it completely destroys a village. But the hardened lava makes the soil fertile, so the Sicilians continue to settle on the slopes of the mountain. Moreover, in 1928 a miracle happened: a stream of hot lava stopped in front of a Catholic procession. In 1930, a chapel was erected on this site and 30 years later the lava stopped in front of the chapel.
In 1981, the regional government in Palermo created a nature reserve around Etna.

7. Montagne-Pelée, Martinique, May 8, 1902
In April 1902, an eruption began in Martinique, and on May 8, a cloud of hot lava, vapors and gases covered the city of Saint-Pierre. Within a few minutes the city was destroyed. Of the 17 ships in the harbor, only one was saved. Of the 28 thousand residents in the city, two were saved, including Opostos Siparis, who was sentenced to death. The powerful stone walls of the death chamber saved the condemned man. The governor pardoned Siparis and for the rest of his life he traveled around the world, talking about what happened.
Napoleon's wife Josephine Beauharnais was born in the city of Saint-Pierre.

8. Nevado del Ruiz, Colombia, November 13, 1985
The main blow fell on the city of Armero, located 50 km from the mountain, which was destroyed in 10 minutes. Of the 28,700 inhabitants, 21 thousand died. Volcanologists warned people about the disaster in advance, but since their forecasts turned out to be wrong several times, the scientists were not believed.

9. Pinatubo, Philippines, June 12, 1991
The volcano was considered extinct and was silent for 611 years. The 1991 eruption killed 875 people and also destroyed a strategic US Air Force base located 18 km from Pinatubo and a US naval base.
The eruption led to a drop in temperature by 0.5 C and a reduction in the ozone layer, in particular to the formation of an ozone hole over Antarctica.

10. Katmai, Alaska, June 6, 1912
One of the largest eruptions of the 20th century. The ash column rose 20 km, the sound was heard 1200 km away in the capital of Alaska, Juneau. At the site of the crater, a lake with a diameter of 1.5 km formed - the main attraction of the Katmai National Park and Preserve, formed in 1980.

Volcanic eruptions

Volcanic eruptions are geological emergencies that can lead to natural disasters. The eruption process can last from several hours to many years. Among the various classifications, general types stand out:

Hawaiian type- emissions of liquid basaltic lava, often forming lava lakes, should resemble scorching clouds or red-hot avalanches.

Hydroexplosive type-- eruptions that occur in shallow conditions of oceans and seas are characterized by the formation of a large amount of steam that occurs when hot magma and sea water come into contact.

Signs of an upcoming eruption

• - Increased seismic activity (from barely noticeable vibrations of lava to a real earthquake).
• - "Grumbling" coming from the crater of the volcano and from underground.
• - The smell of sulfur coming from rivers and streams flowing near the volcano.
• - Acid rain.
• - Pumice dust in the air.
• - Gases and ash escaping from the crater from time to time.

Actions of people during a volcanic eruption

Knowing about the eruption, you can change the path of lava flows using special gutters and trays. They allow the flow to bypass dwellings and keep it in the right direction. In 1983, on the slope of the famous Etna, explosions succeeded in creating a directed channel for lava, which saved nearby villages from the threat.

Sometimes cooling the lava flow with water helps - this method was used by the inhabitants of Iceland when fighting the volcano that “awakened” on January 23, 1973. About 200 men who remained after the evacuation directed fire jets at the lava creeping toward the port. As the water cooled, the lava turned to stone. It was possible to save most of the city of Veistmannaeyjar, the port, and no one was hurt. True, the fight against the volcano dragged on for almost six months. But this is the exception rather than the rule: a huge amount of water was required, and the island was small.

How to prepare for a volcanic eruption

Watch for warnings about a possible volcanic eruption. You will save your life if you leave the dangerous territory in a timely manner. If you receive an ash warning, close all windows, doors and smoke dampers.

Place cars in garages. Keep animals indoors. Stock up on self-powered sources of lighting and heat, water, and food for 3 to 5 days.

What to do during a volcanic eruption

At the first “symptoms” of a beginning eruption, you need to carefully listen to the messages of the Ministry of Emergency Situations and follow all their instructions. It is advisable to urgently leave the disaster area.

What to do if an eruption catches you on the street?

• 1. Run towards the road, try to protect your head.
• 2. If you are driving a car, be prepared for the wheels to get stuck in a layer of ash. Don't try to save the car, leave it and get out on foot.
• 3. If a ball of hot dust and gases appears in the distance, escape by taking refuge in an underground shelter that is built in earthquake-prone areas, or dive into the water until the hot ball rushes on.

What measures should be taken if evacuation is not necessary?

• 1. Do not panic, stay at home, closing the doors and windows.
• 2. When going outside, remember that you cannot wear synthetic things, as they can catch fire, and your clothes should be as comfortable as possible. The mouth and nose should be protected with a damp cloth.
• 3. Don't take refuge in the basement to avoid being buried under a layer of dirt.
• 4. Stock up on water.
• 5. Make sure that falling stones do not cause a fire. As soon as possible, clear the roofs of ash and extinguish any fire that occurs.
• 6. Follow the messages of the Ministry of Emergency Situations on the radio.

What to do after a volcanic eruption

Cover your mouth and nose with gauze to prevent inhalation of ash. Wear safety glasses and clothing to prevent burns. Do not try to drive a car after ash has fallen out - this will lead to its failure. Clear the roof of your house from ash to prevent it from being overloaded and destroyed.

Ashfalls

One of the largest eruptions of the 20th century occurred on June 15, 1991 at Mount Pinatubo (Philippines), a volcano that had been dormant for almost 700 years. The 35 km high Plinian-type eruptive column was the result of an eruption of VEI power 6 and intensity 11.6, leaving a caldera with a diameter of 2.5 km in place of the former summit. The collapse of the vent column led to the formation of numerous pyroclastic flows that spread over a distance of more than 10 km from the volcano and destroyed vegetation over an area of ​​400 km2, but, as described in Chapter 6, the signs of the threat were not ignored and the population was evacuated from the risk zone. As noted, more than 1,200 people who died as a result of this eruption were victims of disease. A 10-centimeter layer of ash precipitation fell over an area of ​​about 2,000 km2. Within this zone, about 300 people died when the roofs of houses collapsed under the weight of the ash, although the buildings were more than 30 km from the volcano.

Experience shows that a 10cm layer of ash deposits on a flat roof can collapse it, especially if the ash becomes saturated with water from the rains that often accompany Plinian-type eruptions. A simple but effective preventive measure can be to clear ash from roofs as often as possible. Ridged roofs are better able to withstand this threat. However, buildings located within the possible fall of even small volcanic bombs with a diameter of a few centimeters can suffer serious damage.

Respiratory threats

Another problem unrelated to volcanic bombs is the respiratory threat to the airways. Inhalation of fine ash particles with diameters less than K) microns leads to irritation of the respiratory tract and is especially dangerous for asthmatics. This threat persists not only during the ash fall, but also while the ash remains loose on the ground, when it can again become airborne from the wind, moving cars, or even from trying to walk on it. Essentially the same problem occurs when small ash particles fall from clouds rising above pyroclastic flows. Rain tends to be very effective at cleaning the air and either washes away fine ash deposits or turns them into mud. This eliminates the respiratory threat, but creates conditions that can lead to the formation of volcanic mud flows known as lahars, which will be discussed later in this chapter.

Volcanoes

Volcanoes - (named after the god of fire Vulcan), geological formations that arise above channels and cracks in the earth's crust through which lava, hot gases and rock fragments erupt onto the earth's surface from the depths of magmatic sources. Typically, volcanoes represent individual mountains composed of products of eruptions.

Volcanoes are divided into active, dormant and extinct. The former include volcanoes that are currently erupting constantly or periodically. Dormant volcanoes include those whose eruptions are unknown, but they have retained their shape and local earthquakes occur beneath them. Extinct volcanoes are severely destroyed and eroded without any manifestations of volcanic activity.

Depending on the shape of the supply channels, volcanoes are divided into central and fissure.

Deep magma chambers can be located in the upper mantle at a depth of about 50-70 km (Klyuchevskaya Sopka volcano in Kamchatka) or in the earth's crust at a depth of 5-6 km (Vesuvius volcano, Italy) and deeper.

Volcanic phenomena

Eruptions can be long-term (over several years, decades and centuries) and short-term (measured in hours). Precursors of eruptions include volcanic earthquakes, acoustic phenomena, changes in the magnetic properties and composition of fumarole gases and other phenomena.

Beginning of the eruption

Eruptions usually begin with increased emissions of gases, first along with dark, cold debris, and then with hot ones. These emissions are in some cases accompanied by an outpouring of lava. The height of the rise of gases and water vapor saturated with heat and debris, depending on the strength of the explosions, ranges from 1 to 5 km (during the eruption of the Bezymianny volcano in Kamchatka in 1956, it reached 45 km). The ejected material is transported over distances from several to tens of thousands of km. The volume of ejected debris sometimes reaches several km3. During some eruptions, the concentration of volcanic ash in the atmosphere can be so great that darkness occurs, similar to darkness in a closed room. This took place in 1956 in the village of Klyuchi, located 40 km from the Bezymyanny volcano.

The eruption is an alternation of weak and strong explosions and outpouring of lava. Explosions of maximum force are called climactic paroxysms. After them, the force of the explosions decreases and the eruptions gradually cease. The volume of erupted lava is up to tens of km3.

Types of eruptions

Volcanic eruptions are not always the same. Depending on the amount of products (gaseous, liquid and solid) and the viscosity of the lavas, 4 main types of eruptions are distinguished: effusive, mixed, extrusive and explosive, or, as they are more often called respectively, Hawaiian, Strombolian, dome and Vulcan.

The Hawaiian type of eruption, which most often creates shield volcanoes, is distinguished by a relatively calm outpouring of liquid (basaltic) lava, forming fiery liquid lakes and lava flows in the craters. Gases contained in small quantities form fountains, throwing out lumps and drops of liquid lava, which are drawn out in flight into thin glass threads.

In the Strombolian type of eruptions, which usually creates stratovolcanoes, along with fairly abundant outpourings of liquid lavas of basaltic and andesite-basaltic composition (sometimes forming very long flows), small explosions are predominant, which throw out pieces of slag and a variety of twisted and spindle-shaped bombs.

For the dome type, gaseous substances play an important role, producing explosions and emissions of huge black clouds filled with large amounts of lava fragments. Viscous andesitic lavas form small flows.

Eruption products

The products of volcanic eruptions are gaseous, liquid and solid.

VOLCANIC GASES, gases released by volcanoes both during an eruption - eruptive, and during periods of its quiet activity - fumaroles from the crater, from cracks located on the slopes of the volcano, from lava flows and pyroclastic rocks. They contain vapors of H2O, H2, HCl, HF, H2S, CO, CO2, etc. Passing through the groundwater zone, hot springs are formed.

LAVA (Italian lava), a hot liquid or very viscous, predominantly silicate mass that pours onto the surface of the Earth during volcanic eruptions. When lava hardens, effusive rocks are formed.

VOLCANIC ROCKS (volcanic rocks), rocks formed as a result of volcanic eruptions. Depending on the nature of the eruption, eruptive or effusive (basalts, andesites, trachytes, liparites, diabases, etc.), volcanogenic-clastic, or pyroclastic (tuffs, volcanic breccias), volcanic rocks are distinguished.

TECTONIC BREAK (tectonic fault), disruption of the continuity of rocks as a result of movements of the earth's crust (faults, shifts, reverse faults, thrusts, etc.).

Depending on the nature of the eruptions and the composition of the magma, structures of various shapes and heights are formed on the surface. They are volcanic apparatuses consisting of a pipe-shaped or fissure channel, a vent (the uppermost part of the channel), thick accumulations of lavas and volcanoclastic products surrounding the channel on different sides and a crater (a bowl-shaped or funnel-shaped depression on the top or slope of a volcano with a diameter of several meters to several meters). km.). The most common forms of construction are cone-shaped (when emissions of clastic material predominate), dome-shaped (when viscous lava is squeezed out).

Causes of volcano activity

The geographical distribution of volcanoes indicates a close connection between belts of volcanic activity and dislocated mobile zones of the earth's crust. The faults that form in these zones are channels through which magma moves to the earth's surface, apparently under the influence of tectonic processes. At depth, when the pressure of gases dissolved in the magma becomes greater than the pressure of the overlying ones, therefore the gases begin to rapidly advance and drag the magma towards the earth's surface. It is possible that gas pressure is created during the crystallization process of magma, when the liquid part of it is enriched with residual gases and steam. The magma seems to boil and, due to the intense release of gaseous substances, high pressure is created in the source, which can also be one of the reasons for the eruption.

Eruption of Mount Etna. Known for its sudden eruptions, Mount Etna on the Italian island of Sicily has been haunting residents of cities located on its slopes since mid-July of this year (2001). A total of 5 craters have opened, from which magma heated to several thousand degrees, volcanic ash and hydrogen sulfide smoke are gushing out. The highest point of emissions is at an altitude of 2950 meters. But from there the stream goes into the deserted Beauvais Valley, which has already been burned by the volcano many times, without threatening anyone. Other pockets are lower, at around 2700, and the red-hot lava slowly flows down a hundred meters below. The worst thing is the crater at 2100 meters - the most inexhaustible of emissions, which threatens to cover the village of Nicolosi. Around the village, bulldozers erected two barriers to the lava. But if the mountain where another crack has opened explodes, it will be very difficult to escape from the town.

Let me remind you: not only Vesuvius was to blame for the infamous death of Pompeii, but also the reluctance of the inhabitants to give up everything in time and flee the city.

The smart Pompeians “evacuated” in time, but the greedy, lazy people remained in the city, where they suffered a painful death.

This story is very instructive, so you should not neglect the danger and try to save your life despite material losses that will never pay for your life.

Bibliography

Ritman A. "Volcanoes and their activities."

Basharina L. A. "Volcanic gases at various stages of volcanic activity."

Zavaritsky A. N. "Igneous rocks."

Maleev E. F. "Vulcanostatic rocks."

Taziev G. "Volcanoes".

Hawaiian-style eruptions can occur along fissures and faults, as in the 1950 eruption of Mauna Loa in Hawaii. They can also occur through a central vent, as in the 1959 eruption of Kilauea Iki Crater on Kilauea Volcano, Hawaii.

This type is characterized by outpourings of liquid, highly mobile basaltic lava, forming huge flat shield volcanoes. Pyroclastic material is practically absent. During fissure eruptions, lava fountains are ejected through faults in the rift zone of the volcano and spread down the slope in streams of low power for tens of kilometers. When an eruption occurs through the central channel, lava is thrown up several hundred meters in the form of liquid pieces like “cakes”, creating shafts and spatter cones. This lava can accumulate in old craters, forming lava lakes.

Volcanoes of this type were first described in Iceland (the Krabla volcano in northern Iceland, located in the rift zone). The type of eruption of the Fournaise volcano on Reunion Island is very close to the Hawaiian one.

Hawaiian eruption type: 1: Ash plume, 2: Lava fountain, 3: Crater, 4: Lava lake, 5: Fumaroles, 6: Lava flow, 7: Layers of lava and ash, 8: Rock layer, 9: Sill, 10: Magma Conduit, 11: Magma Chamber, 12: Dyke

2) Strombolian type

The Strombolian type (from the Stromboli volcano on the Aeolian Islands north of Sicily) of eruptions is associated with a more viscous main lava, which is ejected from the vent in explosions of varying strength, forming relatively short and more powerful lava flows. During explosions they are formed slag cones and plumes of twisted volcanic bombs. The Stromboli volcano regularly throws a “charge” of bombs and pieces (last eruption March 2007) of hot slag into the air.

3) Plinian type

A characteristic feature of this type of eruption is powerful, often sudden explosions, accompanied by the release of huge amounts of tephra, forming pumice and ash flows. Plinian eruptions are dangerous because they occur suddenly, often without prior warning events. Large Plinian-type eruptions, such as the eruption of Mount St. Helens on May 18, 1980, or the eruption of Pinatubo in the Philippines on June 15, 1991, can spew ash and volcanic gases tens of kilometers into the atmosphere. Plinian-type eruptions often produce fast-moving pyroclastic flows.

Plinian type of eruption: 1: Ash plume, 2: Magma conduit, 3: Volcanic ash rain, 4: Lava and ash layers, 5: Rock layer, 6: Magma chamber

4) Peleian type

The Peleian type of eruption is characterized by the formation of enormous red-hot avalanches or scorching clouds, as well as the growth of extrusive domes of extremely viscous lava. This type of eruption got its name from the Mont Pelee volcano on the island of Martinique in the group of Lesser Antilles, where on May 8, 1902, the top of a previously dormant volcano was destroyed by an explosion, and a red-hot heavy cloud bursting out of the crater destroyed the city of Saint-Pierre with 28,000 inhabitants . After the eruption, a “needle” of viscous magma emerged from the crater, which, having reached a height of 300 meters, soon collapsed. A similar eruption occurred on March 30, 1956 in Kamchatka, where the top of the Bezymyanny volcano was destroyed by a grand explosion. A cloud of ash rose to a height of 40 km, and hot avalanches descended along the slopes of the volcano, which, melting the snow, gave rise to powerful mud flows.

5) Gas or phreatic type

Gas or phreatic type of eruptions (also called Bandaisan (Bandai) type), in which fragments of hard, ancient rocks are thrown into the air (new magma does not erupt), is caused either by magmatic gases or is associated with overheated groundwater. Phreatic activity is usually weak, but strong events occur, such as the 1965 eruption of Taal Volcano in the Philippines and La Grande Soufriere on Guadalupe Island.

6) Sub-ice type

The subglacial type of eruption refers to volcanoes located under ice or a glacier. Such eruptions can cause dangerous floods, lahars and globular lava. Only five eruptions of this type have been observed to date.

Subglacial eruption type: 1: Cloud of water vapor, 2: Lake, 3: Ice, 4: Layers of lava and ash, 5: Layer of rock, 6: Ball lava, 7: Magma conduit, 8: Magma chamber, 9: Dyke

7) Icelandic type

The Icelandic type (from the volcanoes of Iceland) is characterized by ejections of very liquid basaltic lava containing pyroclastic material. As a rule, they form flat shield volcanoes. The eruption occurs through fissures. (Hekla, Iceland). A historical example of an Icelandic-type eruption was the eruption of Laki in Iceland in 1782.

8) Type of thunder crack

This type was recorded during the volcanic eruption on the island of Palma in 1915. Occurs on dome volcanoes. Lava flows along the cracks that begin to emerge from the magma chamber, but it is no longer viscous. When cracks reach the crater, explosive eruptions (with explosions) occur.

Hazard criterion

Based on a detailed reconstruction of the eruptive activity of Kamchatka volcanoes, a new approach to defining the concept of “active volcano” has been developed. It is proposed to consider as active those multi-event volcanoes for which at least one eruption has been identified and dated over the past 3000-3500 years. A subgroup of active volcanoes for which there is information about historically documented eruptions or fumarole manifestations, and a subgroup of potentially active volcanoes for which this data is absent, but eruptions over the last 3500 years have been identified, have been identified. Based on similar criteria, potentially active fields of areal basaltic volcanism, regional zones of cinder cones, and concentrated manifestations of multi-extrusive volcanism are also identified. It is proposed to use the obtained data for a new catalog of active volcanoes in Kamchatka, long-term forecast of volcanic activity and associated dangers.

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