A volcano is an opening in the earth, through which magma finds an exit door. Volcanoes can erupt, like Etna, or like Fagradalsfjall in Iceland did recently.
The potential eruption of the Fagradalsfjall volcano had put Iceland on alert. The country prepared for a volcanic eruption. A state of emergency was declared by the authorities, following a series of earthquakes. Since December 18, 2023, the Icelandic volcano has been erupting, without causing any major disruption to air traffic for the moment.
To better understand the current situation in Iceland, here is everything you need to know about volcanoes.
How to define a volcano?
A volcano can first be characterized by its shape: it is a more or less pronounced relief, generally conical in shape. It is characterized by an opening in the earth’s crust. It is a place where the internal dynamics of the Earth are in relation to the surface (aerial or underwater) and the atmosphere of the planet.
The volcano is an exit point for molten rock, called magma. Lava, volcanic ash and gases escape through this opening. Eruptions are mainly caused by gas pressure, “ a bit like carbon dioxide pops the cork from a bottle of champagne », summarizes the Canadian Risk Information Service.
The magma expelled by terrestrial volcanoes is made up of a mixture of molten rock and dissolving gas. Magma results from the melting of solid materials in the Earth’s crust and upper mantle.
How is a volcano formed?
The Earth’s outer layer, the lithosphere, is divided into tectonic plates. These plates are mobile relative to each other, and can collide. Most volcanoes form at the junction of these tectonic plates, we then speak of interplate volcanoes.
Volcanoes forming inside a plate are much rarer, we then speak of intraplate volcanism.
What are the 4 types of volcanoes?
There are 4 types of volcanoes: Strombolian, Vulcanian, Hawaiian and Pelean. They are distinguished according to the type of eruption (depending on the nature of the magma). The same volcano can have different types of eruptions during its existence.
A volcano effusive has eruptions without explosions, with abundant lava flows. A volcano explosive has eruptions accompanied by explosions and lots of ash.
- Volcanoes Strombolians are both effusive and explosive,
- Volcanoes Vulcanians have explosive eruptions without lava flows (too viscous),
- Volcanoes Hawaiian are effusive (or lava),
- Volcanoes peleans are explosive, with projections of rocks, ashes and toxic gases (fiery clouds).
The shape of a volcano directly depends on the type of its eruptions, which can always be of the same type or change over time.
What are the 3 parts of a volcano?
A volcano is made up of 3 main parts:
- THE magma reservoirlocated under the earth’s crust,
- One or more volcanic ventsbinding the reservoir to the surface,
- THE crater.
What are the characteristics of a volcano?
Volcanoes are essential structures on our planet. These are ” the geological architects of the Earth “, sums up National Geographic well. It is estimated that volcanoes are responsible for more than 80% of our planet’s surface.
We distinguish active volcanoes from extinct volcanoes. Active volcanoes, as their name suggests, are likely to erupt on human time scales (year, decade, century or millennium). Active volcanoes alternate periods of activity with periods of dormancy.
How does a volcano erupt?
A volcano is preceded by volcanic earthquakes, called tremors. When magma leaves the magma chamber to rise to the surface, it shocks the walls, displaces solid pieces and causes degassing bubbles. This activity causes seismic vibrations, monitored by seismographs as warning signs of an eruption.
If magma eventually leaves the magma chamber, it is due to a buildup of gas, which mixes with the magma and increases the pressure. When the pressure is too high, the magma is pushed towards the surface, which causes an eruption. The explosion of magma, in the form of lava, can pass through different paths: the main chimney or other chimneys. This can also give rise to a plume made of ash or gas.
During the volcanic eruption, there are different types of volcanic ejecta:
- THE ashes : very fine particles from rock or magma, during spraying,
- THE slag : small pieces of lava solidified in the air or after ejection,
- THE lapilli : fragments of 2 to 64 cm, which come either from the bowels of the volcano, or from solidified lava then pulverized towards the outside,
- THE volcanic bombs : these are pieces larger than 64 centimeters, lava which solidified while it was in the air, after ejection.
How hot is volcanic lava?
When magma exits the magma chamber toward the surface, it becomes lava. This, when it reaches the outside, reaches temperatures ranging from 500 degrees to 1,200°C. When it is on the surface, it is in contact with air and rock, which leads to its gradual cooling and then its solidification.
What volcano is currently erupting?
To find out about active volcanoes and recent earthquakes around the world in real time, you can consult this map. The Global Volcanism Program (GVP), an American research program in volcanology, also maintains a database of terrestrial volcanoes erupting.
This November 13, 2023, volcanoes are attracting a lot of attention. Etna erupted in Sicily: it is the highest active volcano in Europe. A risk of eruption concerns Ireland, with a state of alert triggered in the region of the Fagradalsfjall volcano, which could erupt.
What are the 7 most dangerous volcanoes in the world?
We can cite these 7 particularly threatening volcanoes in the world:
- THE Mount Vesuviusin Italy, one of the rare volcanoes still active in Europe,
- THE Mount Rainierin the United States, closely monitored due to its large glacier (which would add to the flows in the event of an eruption),
- THE Novaruptain the United States, which produced the largest eruption of the 20th century,
- THE Pinatuboin the Philippines, at the origin of the 2nd largest eruption of the 20th century,
- THE Mount Saint Helensin the United States, responsible for the country’s most destructive eruption in 1980,
- L’Agungin Indonesia, erupted for 11 months in 1963,
- THE Mount Fujiin Japan, scrutinized since the 2011 earthquake.
How many volcanoes are there in the world?
10,000 volcanoes have been recorded on the Earth’s continents, of which 1,500 have erupted during the last 10,000 years.
The oceans are crossed by a mid-oceanic ridge, that is to say an underwater volcanic chain, over a distance of 60,000 km. This volcanic chain measures on average 1,500 km in height, but rests at depths of less than 4,000 meters. These volcanoes are the most numerous, but also the least known.
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