What happens if you shake a bottle of soda well and then open it?
Gas pressure will cause the liquid to overflow from the bottle. The higher the pressure inside the bottle, the stronger the liquid will overflow.
Something similar occurs in volcanoes. Molten rocks within the Earth (magma) are expelled, together with gases and water vapor, through crustal flaws.
Volcanoes can emerge in many ways. Many appear on the edges of tectonic plates.
It may happen, for example, that after a shock, part of one plate goes under the other and melts. Thus large underground reservoirs of gases and incandescent magma are formed.
Magma can rise close to the surface, come into contact with water sheets and form steam. If your pressure rises too much, the vapor eventually breaks the surface and releases the magma, which, outside the volcano, becomes lava. Therefore, besides lava and ashes, the volcano expels Steam and various gasessuch as carbon dioxide and sulfur gases.
Some volcanoes erupt only for a few days or weeks. Larger ones can erupt thousands of times over a hundred thousand years or even much longer.
Despite their incredible destructiveness, volcanoes make the surrounding soil extremely fertile, as the ashes and lava, after cooling, function as manure. This is one reason why entire populations settle around volcanoes despite the danger.
In addition, many volcanoes slowly pour lava without explosions. Lava also forms a type of rock, known as igneous rock.
The big challenge for those who study volcanoes (volcanologists) is to predict when the eruptions will occur. Usually before the eruption, there are earthquakes and sulfur gas emissions, which have a typical (rotten egg-like) smell.
There are about 1,300 volcanoes in the world that can erupt at any time, but only about 20 or 30 go live each year.
Some volcanoes, such as Mount Kilimajaro in Africa, are unlikely to erupt again: they are extinct volcanoes.
Mount Kilimajaro, Africa.
Anak Krakatau volcano (meaning "Krakatau child") active in Indonesia
Volcanoes in action
Throughout human history, some volcanoes have been famous for their destructive power. In the year 79, the cities of Pompeii and Herculaneum in Italy were buried by a layer of several meters of lava and ashes released by the volcano Vesuvius. Thousands of people died buried or even intoxicated by the gases of the volcano. The ruins of Pompeii were unearthed in 1738 and many of the city's objects were found to be in good condition.
This volcano became famous because its ashes eventually shaped the body of many victims. By applying plaster in these molds, it was possible to create reproductions of these people as they were at the time of the accident.
Ash and mud shaped the victims' bodies, allowing them to be found just as they were hit by the eruption of Vesuvius.
In 1883, a volcano on the island of Krakatoa in Indonesia caused such an explosion that waves of up to 40 meters in height spread and devastated towns and villages, killing more than 36,000 people. The ashes covered an area of over 800,000 square kilometers. Dust thrown into the atmosphere spread across the earth and blocked part of the sun's rays, causing a temperature drop of about half a degree in 1884. Only after five years, when all the dust had settled, did the climate of the planet returned to normal.
More recently, in 1991, Pinatubo, in the Philippines, also threw a cloud of dust and ash so large that it once again affected the climate of the planet that year.
Volcanoes in Brazil
Brazil is at the center of a large tectonic plate, the South American Platetherefore far from the limits of this plate. The eastern boundary of the South American Plate is positioned at the bottom of the Atlantic Ocean, close to half the distance between Brazil and Africa, while the western boundary is near the western coast of Latin America. The distancing of the boundaries of the South American Plate is the reason why there are no volcanoes currently in Brazil..
However, in past geological times, there was intense volcanic activity, today there are no more active volcanoes in Brazil. Our country was the scene of several volcanic activities, the most recent occurred in the Cenozoic Era (Tertiary), leading to the formation of our oceanic islands, such as Trindade, Fernando de Noronha, Penedo de Sao Pedro and Sao Paulo.
In the Mesozoic Era (between 251 million and 65 million years ago) volcanic activity in Brazil was much more intense, highlighting the following occurrences: Poços de Caldas and Araxá (MG), São Sebastião (SP), Itatiaia and Cabo Frio (RJ) and Lajes (SC); In the South there was one of the largest basaltic spills in the world, covering an area of 1 million km², which goes from the State of São Paulo to Rio Grande do Sul, where there were several manifestations can be observed in the Torres region, as the beautiful basaltic cliffs; The basaltic spills that occurred on the Southern Plateau gave rise to the fertile terra roxa soil; The Amazon Basin has also been affected by volcanic activity in some areas.