Volcanoes are geological structures that can represent a certain risk for the populations that settle around them, so it is necessary to understand the different types of volcanic eruptions, to determine measures and actions before the eruption of a volcano.
Just as there are various types of volcanic eruptions, there are also different types of volcanoes, if you want to know about the types of volcanoes you can click here.
Explosive eruptions
They are those that erupt mainly pyroclastic, have a large amount of volatiles accumulated on the roof of the magma chamber.
In this case, the magma is expelled violently from the volcanic conduit as fragments into the air, this is due to the viscosity of the magma and the amount of dissolved gases.
Magmas are highly viscous, the silica content is very high, therefore, they retain gases and cause an increase in pressure so that the bubbles grow inside, increasing the possibility of an explosive release.
These eruptions form tall columns of ash and gases in the atmosphere, which are spread by the wind and cover large areas, resulting in ash showers, pyroclastic flows, lahars, and debris flows.
In general, the volcano’s chimney is blocked by a plug of lava, this makes the eruptions more violent, sending pyroclastic material to the outside, the gases travel up to 20 km in the atmosphere at several hundred meters per second.
Example:
- Sakurajima volcano erupted explosively on September 9, 1985, in Japan.
Effusive eruptions
In this type of eruption there is a rise and discharge of magma with low volatiles, the magmas are in a fluid state, the gases are not trapped, they can come out freely because there is no pressure, the magma comes out of the conduit without exploding, the lava it spreads slowly over the earth.
Depending on the type of ejected magma, composition, edifice slope, density, and duration of the eruption, the shape, length, thickness, and amplitude of the lava varies. These eruptions are not violent and do not expel pyroclasts.
Example:
- In the Kilauea volcano, you can see these types of eruptions.
Magmatic eruptions
They are those where the magma emerges to the surface, as lava, pyroclastic flows and if divided into: Hawaiian, Icelandic, Strombolian, Vulcanian, Plinian, Peleana.
Hawaiian rash
They are the calmest eruptions, not very explosive, they have a low content of gas and volcanic ash. They occur through one or more cracks in the ground, very close to each other, in which curtains of incandescent magma emerge.
They are characterized by the emission of basaltic lavas, are not very viscous, very fluid and can travel tens of kilometers from their source before cooling.
Lava can be emitted from the crater or from fissures on the flanks of the volcano and can last for hours or even days. In some cases, slag mounds form around emission centers.
The very liquid lavas form lakes in the crater, the volcano that emits them is low in height and has a large diameter at the base.
Its name is due to the Kilauea Volcano on the Big Island of Hawaii, famous for hosting events like these.
Examples of volcanoes that present this type of eruption:
- Mauna Loa volcano, Hawaii
- Kilauea Volcano, Hawaii
- Medicine Lake Volcano, California, USA
Icelandic or fissural eruption
They originate along a fissure in the earth’s crust, which can range from meters to kilometers. The lava that is emitted by the fissure is fluid and can cover great extensions, forming wide plateaus kilometers thick, successive horizontal layers and its relief is flat.
Examples of volcanoes that present this type of eruption:
- Deccan Plateau, located in India.
- Fissure eruption of the Krafla Volcano, located in Iceland.
Strombolian eruption
They are explosive but small eruptions, the lavas are fluid, the gases are released abundantly and violently, the fragments of molten lava are expelled hundreds of meters from the crater.
In this type of eruption, the materials emitted are of a basic composition, which are bombs, slag, a small amount of ash, and an eruptive column is produced that reaches between 1 and 15 km in height.
Lava flows down ravines and slopes, but does not go as far as in Hawaiian eruptions. In addition, it is characterized by presenting rhythmic explosions, which are separated by periods of less than a second to several hours.
They are often associated with small lava lakes, which can collect in the volcano’s vents. The eruptions are not that violent, however it can be dangerous if the bombs or lava flows reach inhabited areas.
These eruptions usually form cinder and scoria cones, with heights of 100 to 200 meters.
Example:
- Stromboli volcano, located in the Lipari islands, north of Sicily, Italy. Volcano for which this type of eruption receives its name.
Vulcanian eruption
They are brief, violent and relatively small eruptions, the viscous magma is of intermediate composition (dacite, andesite or rhyolite). These eruptions cause the fragmentation and explosion of the lava plug in the volcano’s chimney or a dome.
These eruptions are powerful explosions, the ejected material can travel at more than 350 meters per second and rise a few kilometers into the air, forming an eruptive column from 3 to 20 kilometers high. It is characterized by producing an eruption in the form of a cloud similar to a fungus or mushroom.
The erupting volcano ejects tephra, lapilli, large amounts of hot ash clouds, ballistic projectiles, and gases.
The beginning of a Vulcan activity is the creation of a dome, forming pyroclastic flows as it grows. At the beginning there are explosions of short duration (minutes to hours) expelling blocks and bombs, due to the pressure of the gases in the viscous magma the lava plug explodes, after this, the eruption is calmer and more continuous.
They can also be repetitive, proceed to larger explosive eruptions, and can last for days, months, or years.
Example
- Vulcano volcano, is located on the Lipari islands, north of Sicily in Italy. The name of the type of eruption is due to the eruptions of this volcano.
Plinian eruption
They are the most violent and largest of all types of eruptions, they are extremely destructive and can destroy the top of the volcano and form a caldera. They release enormous amounts of energy, are associated with highly viscous magmas (dacite and rhyolite) and are caused by the fragmentation of gaseous magma.
These eruptions manage to create columns up to 50 km high of gas and ash that can disperse or fly hundreds or thousands of miles from the volcano. These columns have the shape of a mushroom and are composed of volcanic gases and water vapors, such as sulfur or chlorine.
Eruptions of this type produce ash falls, ballistic projectiles, slag, and pyroclastic flows, which destroy everything in their path, affecting large areas. After the eruption, the magma chamber is partially empty, so the volcano may later enter a period of inactivity.
Its name is due to the account made by the young Pliny of the eruption of Vesuvius, which occurred in the year 79 AD.
Examples of volcanoes that present this type of eruption:
- Vesuvius volcano, buried the city of Pompeii. It is located in Italy.
- Huaynaputina volcano, is a stratovolcano, located in the department of Moquegua, in southern Peru.
- Teide volcano, located on Tenerife island, Spain.
- Mount Fuji is located on the island of Honshu, Japan.
Peleana rash
They are produced because the highly viscous lava solidifies quickly, which produces a plug or dome in the crater. Inside the volcano, the pressure increases due to the accumulation of gases and causes ruptures or lateral cracks through which the lava comes out.
Its eruption is explosive, violent and intermittent, spewing very viscous lava. These eruptions are characterized by presenting dome collapses, which generate pyroclastic flows or burning clouds that are made up of a mixture of gases, ash, and water vapor that destroy everything in their path.
These flows can reach speeds of 100 to 200 kilometers per hour and have temperatures of 500°C.
Examples of volcanoes that present this type of eruption:
- Pelée Mountain, a volcanic summit located on the island of Martinique, in Caribbean waters. They are named after the Pelée mountain from the 1902 eruption.
- Merapi volcano, is located in Indonesia.
- Sinabung-Sumatra volcano, located in Indonesia.
Phreatomagmatic eruptions
They are caused by the direct interaction of magma and water. They occur in oceans, lakes or groundwater. It is divided into three types of eruptions: surtseyan, submarine and subglacial.
Surtseyan eruption
They are hydromagmatic eruptions, in this case the magma or lava interacts with the water explosively. The emitted lavas are of basaltic composition, most of the oceanic volcanoes are basaltic.
In general, these occur when the surface of the water breaks due to the growth of an underwater volcano, when this happens the high temperature of the magma causes the water to immediately turn into steam, the water comes into contact with the hot lava and explodes. violently, creating columns of ash, steam, pyroclasts, more or less pulverized fragments of rock and slag.
This type of eruption forms tuff rings, volcanic cones, and if they emerge, they end up forming a new island.
Examples:
- Volcanic island of Surtsey, erupted off the south coast of Iceland.
- Submarine volcano in Tonga, erupted in Oceania.
Underwater eruption
These types of eruptions are more frequent than eruptions on the Earth’s surface. The largest number of volcanic eruptions on the planet are underwater.
In general, they go unnoticed because in the abyssal zones the high pressure of the water causes the dissolution of the gases and slows down the projectiles, for this reason no sign of the eruption can be seen on the surface of the sea.
In the event that this type of eruption occurs in a lake, it can be observed on the surface.