Volcanic eruptions is a geological formation that occurs over channels and cracks in the earth’s crust, along which molten rocks (lava), ash, hot gases, water vapor and fragments of rock erupt onto the earth’s surface.Currently there are about 500 active volcanoes in the world – most of them are concentrated in the region of the Pacific Ring of Fire. It is estimated that about 500 million people live in the zone of activity of such volcanoes.
Volcanoes can be dangerous if they erupt. They can throw gases, rocks, ash and lava. Some can throw stones and hit people, damage house roofs, block roads and damage to agriculture. At other times, they can produce ash rains, sometimes accompanied by toxic gases that cause skin burns, prevent breathing and irritate the eyes. They can also lower lava flows, usually at low speed, which destroy everything in their path. Through the riverbeds located on the slopes of the volcano, mud, stones, trees can be lowered.
The main indicators of the volcanic eruption force are the volume of erupted products (tephra) and the height of the ash column. The eruption force is measured in points from 0 to 8. A rating of 0 corresponds to an eruption with a volume of emissions of less than 10,000 m3. With each next point the volume increases by an order of magnitude. When estimated at 8 points, the volcano is called supervolcano, the volume of the ejected substance is more than 1000 km3, and the ash column rises to an altitude of more than 25 km. Eruptions with a VEI score of 6 or more can cause a volcanic winter effect — a global cooling on a planet-wide scale.
By the nature of the eruption, which depends on the temperature of the magma, its composition, gas content, volcanoes are:
- effusive – liquid lava quietly pours out from craters or cracks to the surface and, while freezing, forms covers of up to several hundred square kilometers;
- explosive – magma, approaching the surface, heats up and boils – an explosive eruption of a volcano occurs, during which gases, crushed rocks (pyroclastic materials), and ash are released from the crater;
- extrusive – viscous lava under low temperature is slowly squeezed out to the surface, forming a volcanic dome. The process can end with explosions.
At the location of volcanoes distinguish terrestrial, underwater, subglacial, etc.
The volcanic apparatus consists of the following parts:
- magma chamber (in the crust or upper mantle);
- Vent – outlet channel through which magma rises to the surface;
- cone – elevation on the surface of the Earth from volcanic ejection products;
- crater – a recess on the surface of a volcanic cone.
The shape of the volcanoes are: central, erupting from the central pinhole, and fracturing, whose devices have the form of gaping cracks and a number of small cones. The structure and behavior of a volcano depend on many factors. Many tops of volcanoes are formed by lava cones, not craters. Thus, volcanic materials and gases can erupt anywhere on the surface.
Consider in detail some types of volcanoes.
The volcano with a flat fault at the top in the form of a line through which the lava erupts is called a vent crack.
The shield volcano, due to the wide shield-like profile formed by the eruption of inviscid lava, makes it possible to spread lava long distances from the crack, however, in most cases, this does not lead to catastrophic consequences, since there is no large amount of silicon oxide in inviscid lava. This type of volcano is distributed mainly in the ocean, and not on the continents.
The lava dome is formed during the eruption of inviscid lava. Sometimes this type of volcanoes form in the crater of a volcano that erupted some time ago, such as St. Helens volcano, located in the US state of California, but they can also be formed independently of previous eruptions, such as the active Lassen Peak volcano in North America, one of the largest lava domes on Earth (610 m). The activity of this type of volcanoes is accompanied by strong explosive eruptions, but their lava basically does not spread far from the hydrothermal corridor.
Slag cone is formed as a result of the eruption of small pieces of slag and pyroclasts (both formations resemble small cylinders, which gave the name to the volcano), forming around the hydrothermal corridor. The eruption of this type of volcanoes takes a short time and forms a cone-shaped hill with a height of 30–40 m. The most prominent examples of such volcanoes are Paricuti volcano in Mexico, Michoacan state, and Sunset Crater in the USA, Arizona.
Composite volcanoes or stratovolcanoes are high conical structures consisting of layers of lava, slag and ash, the so-called strata – strata. As a result of volcanic activity, slag and ash are deposited on top of a mountain in layers (ash over slag), and lava flows down a layer of ash, where it cools and hardens, then the process repeats. Typical examples of stratovolcanoes are Mount Fiji in Japan, the Mavon volcano in the Philippines, and Mount Vesuvius and Stromboli in Italy.
Underwater volcanoes are mostly located at great depths, where huge masses of water do not allow steam and gases to erupt to the surface. Lava under water is formed in the form of balls, which is a typical characteristic of underwater volcanoes. Underwater volcanoes often form columns above the hydrothermal corridor, which can become so high that, protruding above the surface of the oceans, they can form new islands.
Mud volcanoes are formed during the eruption of liquids and gases. Such volcanoes are found mainly in the oil-bearing and volcanic areas, often fumaroles (cracks and holes located in the craters, on the slopes and at the foot of the volcanoes and serve as sources of hot gases), passing through layers of clay and volcanic ash. Gases released with dirt can spontaneously ignite, forming torches. Distributed in the Caspian (Apsheron Peninsula and Eastern Georgia), the Black and Azov Seas (Taman and Kerch Peninsulas), in Europe (Italy, Iceland), in New Zealand and America.
Subglacial volcanoes are formed under the ice caps. The erupted lava flows over large lava boulders, which were formed as a result of previous volcanic eruptions. During such eruptions, ice caps melt and the lava at the top goes down, leveling the surface and forming a flat top. Typical examples are the mountains of Iceland as well as British Columbia.
The combination of several properties allows us to talk about the characteristics of the eruption of a volcano, which made it possible to identify characteristic types of volcanoes that have the appropriate type of eruption:
- Hawaiian type (Mauna Loa volcano, island of Hawaii). Magma flows relatively calmly, without explosions, and forms flat shield volcanoes;
- Stromboliap type (Stromboli volcano, Lipari Islands). The outpourings of lava are accompanied by explosions in which large solid pieces of rock are thrown – bombs and basalt slag;
- volcanic ( Plinian) type (Vesuvius volcano, Italy). Powerful and sudden explosions of the volcano are accompanied by emissions of a large amount of tephra – different in size rock fragments with the formation of large amounts of ash;
- Peli type (Mont Pele volcano, Antilles). During the eruption, huge avalanches of hot substance descend from the volcano. Near the crater lava accumulates, forming a volcanic (extrusive) dome. Volcanic gases and ashes burst out and form “scorching clouds”, the temperature inside of which reaches 400 ° С;
- type of Etna ( Etna volcano, Sicily island). The slopes of the volcano are covered with numerous cracks, along which hot lava makes its way to the surface, forming numerous parasitic craters.
For the forecast of eruptions make maps of volcanic danger. Frequent volcanic earthquakes, swelling, bending or changing the inclination of the surface, increased emission of volcanic gases and changes in their composition may indicate an eruption of a volcano.
The actions of the population under the threat of volcanic eruption
- Follow the warning of a possible volcanic eruption.
- It is necessary to leave the dangerous territory in time.
- When receiving warning of ash fall, close all windows, doors and smoke dampers.
- Before leaving the apartment (house), it is necessary to turn off the heating devices and gas, if the stove was heated – to extinguish it; then you need to dress children, old people and dress yourself, take the necessary things, a small supply of food, documents and go outside to the place of evacuation.
- It is necessary to stock up on sources of lighting and heat with autonomous power, water, food for 3-5 days.
- Prepare a first aid kit.
Population actions during volcanic eruption
- Protect the body and head from stones and ash.
- Avoid the banks of rivers and valleys near volcanoes, try to stick to elevated places in order not to fall into the zone of flooding or debris flow.
- Find shelter from a scorching cloud η water or in an underground shelter.
Population after the volcanic eruption
- Close the respiratory organs with the simplest means of protection in order to exclude ash inhalation.
- Wear safety goggles and clothing to protect against burns.
- Do not use the units and mechanisms after the fall of the ashes – this will lead to their failure.
- Clear the roof of the house from ashes in order to prevent its overload and destruction.
What to do in case of volcanic eruption?
How do we prepare?
Let’s develop the family emergency plan together. It is simple and can save the life of our family.
- With family members prepare the emergency case, with non-perishable food, radio, focus, personal documents, medicines and protectors to cover the nose.
- Locate temporary shelters, evacuation routes and safe areas in your community.
- Respect the sites declared dangerous.
- Consult the Municipal and Local Emergency Committees, about the evacuation system and animal shelter centers.
- Establish an evacuation route, away from rivers and streams and possible shelters.
- Let us notify the local authorities or 9-1-1 of any anomaly or observation about the behavior of the volcano.
- Do not get carried away by false rumors of unauthorized persons.
TIPS FOR FARMERS
In case of eruptions of volcanic ash and acid rain:
- Use pH marker tapes to detect acidity in atom water, dew and rain. If there is acidity, use buffer regulators with agricultural and foliar oils.
- If ash falls, if it is wet, wash thoroughly with a good pressure pump; if it is dry, shake it with blowers or use branches to remove it from the leaves.
- Report any damage to your nearest agricultural services agency.
- Be aware of the recommendations issued by the competent authorities.
- Do not wait to lose your crop. Be attentive and don’t hesitate to ask for advice.
TIPS FOR LIVESTOCKERS
In case of eruptions of volcanic ash and acid rain:
- Extreme measures to guarantee food for your livestock. Buy bales of hay and store them in dry places. Make silages and, as far as possible, dry “kikuyo” grass in plastic tents.
Blast your animals during the days when there is a major drop in acid rain or volcanic ash.
- In the area where volcanic ash falls, shake the pastures that the cattle will consume. Pass it through water tanks before chopping so that the minerals present in the ash do not affect the digestion of your animals.
- Approve molasses and other energy.
Let’s respond on time
- If we observe any change in the volcano, such as new fumaroles, hot springs, dry wells, ashes or landslides, let us know to the authorities.
- Avoid breathing harmful gases or fine dust, using masks or cloth moistened with water or over the mouth and nose.
- Protect the head and shoulders with a hat and thick coat.
- Wash the vegetables that we are going to consume.
- Let us keep abreast of the activity of the volcano through the CNE reports, disseminated through the media (radio, TV and others).
- Do not use the phone, only in a very urgent case.
- If we are in a risk zone, let’s prepare for an eventual evacuation.
- If the volcano is erupting, let’s stay inside the house and breathe through a damp cloth and protect our eyes.
- Close all windows, doors and ventilation ducts of the house.
- Cover the spaces around windows and doors with wet cloths.
- Let’s wear long-sleeved shirts and long pants.
- Cover the water tanks to avoid contamination with ash.
- Limpiemos ash from roofs, patios and streets, placingin bags. We must never throw the ash into the drains to prevent them from clogging up.
Let’s stay in a safe place and stay tuned to the official report of the CNE where it indicates that everything has returned to normal
- We must be aware that the habitation of our home and surrounding areas must be coordinated with local agencies and the municipality.
- Avoid areas where volcanic ash has fallen. In case it is necessary to remain there, we cover the mouth and nose with a mask, keep the skin covered and wear eye protection goggles.
- Let’s clean the ash from the roofs since it is very heavy and could cause houses to collapse.