You volcanoes are natural phenomena that are located in areas where the tectonic plates converge, that is, come into contact. These phenomena, from the interior of Earth's crust, release a viscous and extremely hot liquid, magma. When magma is expelled to the surface, it is called lava.
Read too:Why do volcanoes erupt?
How is a volcano formed?
Most volcanoes have a very similar shape: mountains with a cone shape and an opening at the top, the highest point of the structure. Yet, volcanoes and mountains can have different geological formation processes, although a volcano is a mountain, not every mountain is a volcano.
Volcanoes form through the accumulation of magma inside the Earth, in contact areas of tectonic plates. These plates are on top of the magma, the viscous part of the mantle responsible for the movement of these huge rock blocks. The pressure and heat in the mantle and the circular movement of the magma generate the buildup that needs to be expelled to the surface in some way.
Thus, slits are opened, in a cone shape, so thatsand magma hits the surface, generating volcanic eruptions. When this magma, of basaltic composition, reaches the surface, we have lava, a set of molten rocks at an extremely high temperature. These cracks occur in the tectonic plate contact, areas we call subduction zones. In these zones, the less dense plate sinks under the heavier one, usually oceanic plates beneath continental plates, respectively.
However, there are volcanoes in plate clearance areas, by the same process of pressure and magma accumulation already mentioned. When oceanic plates move apart, we have undersea volcanic eruptions. These seafloor eruptions are responsible for the expansion of the ocean floor, accounting for 80% of all volcanism on the planet.
As an example of undersea volcanic eruptions, we cite the Mid-Atlantic Range, located in the Oocean Atlantic and which marks the boundaries between the South American and African plates.
parts of the volcano
Despite having varied forms and occurring in different areas of the globe, volcanoes have a common structure.
Volcanoes are made up of four parts:
Crater: summit of the volcano through which material is expelled during volcanic activity;
Chimney: passage through which the magma rises from the magma chamber to the chimney;
Cone: geological structure of volcanoes;
Chambermagmatic: reservoir, below the volcano, of molten rock and magma from the mantle. At this point, when there is pressure exerted from the mantle in relation to the rocks, the magma is expelled, passing through the chimney to the crater, reaching the surface in the crust or in the continent, whether in the ocean.
See too: What is the center of the Earth like?
Types of volcano
Each volcano has its peculiarity according to your level of activity. However, the division of volcanoes based on this criterion is questionable, as we cannot accurately predict that a volcano will not go into action, launching volcanic eruptions.
For educational purposes, volcanoes are classified into three types:
Active: that are unstable and in constant volcanic activity, expelling gases, lavas or pyroclastic flows;
Inactive (extinct): that they have not erupted for a certain time and that, according to forecasts by volcanologists, they will not erupt anytime soon;
sleepers: that are not in volcanic activity, but that, at any time, can show signs of activity.
Eruption
Volcanic eruptions are frightening. Estimates indicate that 10% of the world population live in areas close to volcanoes, active or not.
Such eruptions in most volcanoes don't just happen. A volcano, when it comes into activity, gives signs that he will soon show his strength. Earth tremors, openings at the top of the geological structure, explosion of gases and clouds of smoke are some examples of these signs.
Upon erupting, a volcano destroys everything it reaches with lava, pyroclastic flows, clouds of sulfur dioxide, carbon dioxide and/or hydrochloric acid.
The lava expelled by the volcano generates a strong torrent, which descends from the crater, located at the highest point, and burns away everything it finds, from vegetation to entire cities. People are burned alive, instantly.
The gases generated by the explosions, like sulfur dioxide, reach hundreds of kilometers, which may asphyxiate the population or poison the lungs. Depending on the location and range of these gases and smoke clouds, urban life is disrupted, such as in ports and airports near volcanoes.
Volcano in Brazil
Most of the world's active volcanoes are located in contact areas of tectonic plates. As Brazil is at the center of the South American plate, there are no active volcanoes in our country.
However, a few million years ago, our territory was the target of some volcanic eruptions, especially the Southeast it's the South from the country. At oceanic islands off the Brazilian coast are of volcanic origin, formed millions of years ago. According to the Mineral Resources Research Company (CPRM), with the exception of Abrolhos, the others Islands they have a basaltic composition, suggesting volcanic activity.
Also access: Why are there no volcanoes in Brazil?
Major volcanoes in the world
Volcanoes sharpen human curiosity since ancient times. Passing through ancient civilizations, which venerated them as mortal deities, to today's tourists, who search for the more varied adventures, volcanoes draw attention for their beauty, when inactive, and for their thunderous force, when active.
In this way, these natural phenomena spread across the planet reveal the beauty and destruction that simultaneously exist on Earth.
According to the CPRM, together with the Geological Survey of Brazil, there are about 20 extremely active volcanoes around the world and approximately others 1500 active, dormant or inactive.
See some of the top volcanoes in the world.
Mauna Kea, U.S
Osorno, Chile
Masaya, Nicaragua
Kilimanjaro, Tanzania
Mount St. Helena, United States
Mount Fuji, Japan
Kilauea, United States
Vesuvius, Italy
Krakatoa, Indonesia
Ubinas, Peru
Guys, Colombia
Turrialba, Costa Rica
Colima, Mexico
Popocatepetl, Mexico
Poás, Costa Rica
Curiosities about volcanoes
Let's look at some fun facts about this phenomenon of nature.
There is an area in the world known as the Circle of Fire, as it has the highest occurrence of volcanoes on the planet. This area is located between the Asia and the west part of America, in the Pacific Ocean.
The countries with the highest number of active volcanoes in the world are: Chile, Japan and Indonesia.
For 111 years, the Yasur volcano in Vanuatu has been erupting. It is the longest active volcano in the world.
The highest volcano in the world, in height, is Ojos del Salado, with 6,893 m in height, in Chile.
The largest volcano in the world, in width, is Mauna Loa, Hawaii, with 4,169 m high and 90 km wide.
In 1815, a volcano in Indonesia killed 100,000 people. It is the largest number of fatal victims in the history of volcanoes.
Kilauea, Hawaii, is the volcano with the most recent seismic activity, as well as being the most visited in the world.
In history, two cities were completely razed by a volcano: pompandwas going and Herculaneum. The volcano in question is Vesuvius, which has not erupted since 1944.
Volcanoes were once movie stars too. Among the films that had volcanoes as a backdrop for their stories, we can mention:
- Dante's Hell (1998)
- Volcano - the fury (1997)
- what i most desire (2011),
- Pompeii (2014).
The professional who studies volcanoes is the volcanologist.
The word volcano has its origins in the Roman god Vulcan, god of fire.
See too: Why do tectonic plates move?
solved exercises
Question 1 - (FGV) Earthquakes, volcanoes and mountain building are extremely important geological activities that occur on Earth. Look at the location of the seismic zones and the main volcanoes on the map.
Based on this map and your knowledge, it is CORRECT to state:
A) Only the movement of separating tectonic plates causes earthquakes.
B) Only the movement of separation of the tectonic plates causes volcanism.
C) Most of the seismic zones and volcanoes are located in the center of the tectonic plates.
D) Most of the zones of intense seismic activity and volcanoes are located on the edges of tectonic plates.
E) Zones of intense seismic activity are distributed randomly, with no evident relationship with the movement of tectonic plates.
Resolution
Alternative D. Most volcanoes are located in contact areas of tectonic plates.
Question 2 - (UFSM)
The Quick Bird satellite was positioned over Sri Lanka at the time of the tsunami in December 2004, allowing it to record images of the catastrophe in real time. It would be reasonable to assume that, if this event had occurred in countries like the US and Japan, the tragedy could be minimized, as these countries have tsunami detection systems and alert. However, an interesting fact occurred in relation to this tsunami: there is no record of animal death (except for some domestic animals, whose instincts tend to attenuate). The birds flew far away. Elephants, even tethered, broke the chains and fled before the waves reached the shore. Currently the Chinese use cameras 24 hours a day to observe the movement of animals in parks and zoos and use these behavioral changes as a warning system for beings humans.
TERRA, Lygia et al. Connections. São Paulo: Modern, 2008. P. 163. (adapted)
Check the statement that presents a conclusion from the analysis of the text.
A) Earth surveillance technologies such as GMES (Global Monitoring of the Earth System) have been effective in saving lives from natural disasters.
B) The widespread use of monitoring technologies in Chinese territory has meant a reduction in natural disasters in that country.
C) Natural disasters, such as volcanoes, cyclones, earthquakes, landslides, extreme droughts and floods, can be avoided considering the union of technologies and the "sixth" sense of animals.
D) Despite all the technology developed by human beings, we still depend a lot on nature.
Resolution
Alternative D. Even with all the technology, we cannot accurately predict natural phenomena such as earthquakes and volcanic activity, which makes us very dependent on nature.
