Volcanoes are fascinating geological structures that connect the Earth's deep interior with its surface. These gigantic natural vents are not only responsible for sculpting imposing volcanic landscapes, but have also influenced human history through their eruptions. To better understand how they behave, geology classifies them into different types based on various criteria. Among them, volcanoes stand out. hydromagmatic, fissures y underground, which present unique characteristics both in their formation and in their eruptive activity.
This classification allows us to analyze the origin, eruptive dynamics, and risks associated with each type, which is essential for natural disaster prevention and territorial planning. Furthermore, learning about historical cases of eruptions helps us understand the real impact these phenomena have on the environment and the population. In this article, we take you on a complete geological journey to discover how volcanoes are classified, their main types, and what real-life examples teach us important lessons. If you'd like to delve deeper into the topic, we invite you to read about volcanism and its importance.
How are volcanoes classified?
Volcanoes can be classified using various geological and volcanological criteria. Among the most important are:
- According to the type of eruption: magmatic, phreatomagmatic or phreatic.
- Due to its shape and structure: shield, stratovolcano, cinder cone, dome, etc.
- According to your activity: active, inactive or extinct.
- By the type of lava and products emitted: basaltic, andesitic, dacitic or rhyolitic.
Among the more specific classifications are the hydromagmatic volcanoes, fissure volcanoes and underground or subglacial eruptions, which are classified as eruptive types defined by the way magma and other elements such as water interact. To better understand the different characteristics, you can consult the article on types of volcanoes.
Volcanic eruptions: explosive and effusive
One of the key aspects in volcanology is to differentiate between explosive eruptions y effusive:
- Explosives: They are characterized by the violent release of solid fragments, gases, and ash. This occurs when the magma is viscous and has a high silica content, which traps gases and generates pressure.
- effusive: The magma is fluid and low in gases. Lava flows gently from the crater or fissure, forming extensive flows but without large explosions.
Hawaiian volcanoes, for example, represent a clear type of effusive eruption, while Plinian or Pelean volcanoes involve explosive eruptions of great destructive power. Understanding these mechanisms is crucial, and for more information on their classification, you can read the article on Tambora volcano.
Magmatic eruptions: classification and examples
These eruptions occur when magma rises to the surface, generating different types of volcanoes depending on their behavior. Let's look at the main ones:
Plinian eruptions
They are the most violent and destructive. They are characterized by eruptive columns that can reach between 20 and 30 kilometers high. They alternate explosive and effusive phases, with projection of ash, gases, lava and pyroclasts. A historical example was the eruption of Vesuvius in 79 AD that buried Pompeii and Herculaneum. These eruptions are also informative for the study of dormant volcanoes, which you can explore further here. exploring dormant volcanoes.
Other Plinian volcanoes include the Teide (Spain), Popocatepetl (Mexico), Fujiyama (Japan) and Mount Saint Helens (USA).
Pelean eruptions
They owe their name to the volcano Mount Pelee in Martinique. These are extremely explosive eruptions, with very viscous magma that clogs the vent. The eruptions generate burning clouds or pyroclastic flows capable of destroying everything in their path. The 1902 eruption devastated the town of Saint-Pierre. This type of activity is vital to understanding the volcanism and igneous rocks.
Vulcan eruptions
The less fluid and more viscous magma causes the crater to clog, building up pressure and triggering violent explosions. The lava fragments rapidly, generating dense ash clouds and volcanic bombs. They often form steep cones. An example: the Vulcano volcano in the Lipari Islands.
Strombolian eruptions
These eruptions alternate between mild explosive phases and lava flows. The lava is more viscous than in Hawaiian types but retains a certain fluidity. Stratified cones known as stratovolcanoes are formed. The volcano Stromboli, in Italy, represents this type and has been active for centuries. To better understand its eruptive activity, you can read about it here. what is lava.
Hawaiian eruptions
Magma emerges through fissures or volcanic tubes with continuous flows of very fluid, low-gas lava. These are the quietest eruptions and are associated with volcanoes of low slope and large extensionProminent example: Hawaiian volcanoes like Kilauea.
Icelandic or fissure eruptions
This type of eruption occurs throughout large cracks or fissures in the crust, where very fluid lava emerges. The flows extend to form thick volcanic plateaus. Recognized examples include the Deccan Plateau in India and the Laki fissure in Iceland.
Phreatomagmatic eruptions: when magma mixes with water
This type of eruption is generated by the interaction between magma and water (from seas, lakes, or groundwater). This sudden mixing produces high-pressure steam that results in violent explosions. Three subtypes are identified:
Surtseyan eruptions
They occur in shallow waters (such as the sea or lakes) and produce explosions due to direct contact between magma and water. Their name comes from Surtsey Island (Iceland), which was formed in 1963 after an eruption of this type. They can even form new volcanic islandsThese eruptions are especially interesting for the study of the origin of new islands.
Underwater eruptions
Very common but barely visible. Water pressure prevents gases from being easily released. They usually go unnoticed, except when there is a large release of magma or when they occur in lakes, where their effects are more noticeable.
Subglacial eruptions
They develop under large layers of ice, such as glaciers. Magma melts the ice and accumulates water, which can cause explosions or form subglacial lakes. This type of eruption is associated with volcanoes in Iceland or Antarctica. They usually have flat tops and steep sides.
Phreatic eruptions: without the presence of magma
Phreatic eruptions are volcanically explosive with no outlet for magmaThey occur when water comes into indirect contact with a volcanic heat source, such as deep magma, and suddenly turns into steam, generating a massive explosion.
This type of eruption throws water, ash, rocks, and steam into the air, but without emitting lava. Although less spectacular, they can be very dangerous because do not present clear previous signs.
Emblematic cases of volcanic eruptions
Below, we review some of the most documented eruptive events that perfectly illustrate the different types of volcanoes and eruptions:
Quizapu Volcano (Chile, 1932)
A Plinian eruption that launched a 30 km high ash column, affecting regions of Argentina and Brazil. It caused significant socioeconomic damage and a global drop in temperature in the Southern Hemisphere.
Hudson Volcano (Chile, 1991)
Large explosive eruption, with dispersion of 4 km³ of tephra which reached more than 1200 kilometers. It caused severe damage in Patagonia, affecting livestock and generating desertification.
Planchón-Peteroa Volcano (Argentina-Chile, 1991)
An eruption phreatomagmatic This earthquake created a new crater and dispersed ash at an altitude of less than 1000 meters. Although of low intensity, it had a strong impact on livestock and prompted precautionary evacuations.
Lascar Volcano (Chile, 1993)
Subplinian eruption with an eruption column measuring up to 23 km. It dispersed ash as far away as Argentina and caused pyroclastic flows in Chile. This event was one of the largest in northern Chile.
Chaitén Volcano (Chile, 2008)
Explosive eruption after more than 9000 years of inactivity. formation of a siliceous dome and its subsequent collapse generated pyroclastic flows and lahars. The city was completely evacuated.
Puyehue – Cordón Caulle Volcanic Complex (Chile, 2011)
Fissure eruption with eruptive column of up to 14 km and ashfall in Argentina. Bariloche Airport was closed for seven months. There were also pyroclastic flows and continuous emissions for months.
Copahue Volcano (Argentina-Chile, 2012)
Eruption initially hydromagmatic which evolved into a Strombolian earthquake. A pyroclastic cone formed inside the crater, and ashfall was recorded up to 50 km away. The town of Caviahue was temporarily evacuated.
Calbuco Volcano (Chile, 2015)
Violent subplinian eruption with 17,5 km columnPyroclastic flows, lahars, and mass evacuations occurred. In Argentina, ash caused air disruptions and damage to livestock.
These events demonstrate that The classification of volcanoes according to their eruptive behavior is an essential tool for the study and management of volcanic risk. From gigantic Plinian explosions to silent, extensive Hawaiian-style eruptions, each type of volcano represents unique geological dynamics with equally diverse consequences.
