Volcanoes are ruptures in the earth’s crust that allow magma to flow upwards and are classified both by the type of its structure and by the type of activity or eruption they present . It must be taken into account that the same volcano can combine different structures and change the type of eruption. The official classification according to its form is:
Composite volcanoes or stratovolcanoes
Main characteristic: periodic explosion
It is known as a stratovolcano because the composite strata or layered structure are formed due to the eruptive material; that is, these volcanic formations take place due to the amount of eruptions that occur over several thousand years. The lava flows from these volcanoes are steep. Stratovolcanoes have relatively steep sides and often have a very pronounced cone shape . They are formed from viscous and sticky lava that does not flow easily, so it accumulates around the vent forming a volcano with impressive peaks. The most common type of rock in stratovolcanoes is andesite (named after the Andes Mountains). Considering that magma is very viscous and flows slowly , it can clog the crater and, after increasing the pressure, cause an explosive eruption. It is the most common type of volcano on our planet.
Known stratovolcanoes: Pico del Teide, Arenal volcano, Popocatépetl, Misti, Krakatoa, Monte Helena, Monte Vesubio or Chimborazo …
Shield volcanoes
Main characteristic: low explosiveness of lava
These huge volcanoes are formed in areas where the lava is expelled in a fluid way; It is a low viscosity liquid lava. Its base is very wide and presents a gentle slope, as a result of the different flows. Its slopes, therefore, are highly developed horizontally . Most shield volcanoes are formed from flowing basaltic lava flows and are the result of many layers of lava flows. They are large structures that are naturally circular fan-shaped, hence they look like a shield. Although they can reach quite significant sizes , they are not as dangerous as it might seem. This is because the eruption of lava from shield volcanoes is not accompanied by pyroclastic material (bursts of gas and particles). These volcanoes slowly accumulate over time and over thousands of lava flows. Magma does not erupt explosively and the cone can form in a very small area (less than 5 square kilometers).
Known shield volcanoes: Mauna Kea, Mauna Loa. Hualalai, Kohala volcano, Killauea, Cerro Azul …
Boilers
Main feature: a large crater
These are large volcanic depressions between 5 and 15 kilometers in diameter formed by an explosion or collapse of the magmatic chamber or even by erosion. The magma is stored under the volcano in a magma chamber. When a very large explosive eruption occurs that empties the magma chamber, the roof of the magma chamber can collapse and form a depression or bowl with very steep walls on the surface. What remains is the boiler. Caldera volcanoes are characterized by having rhyolitic magma that forms at relatively low temperatures (750–850ºC) and is thick.
Known calderas: Mount Tambora, Taupo volcano, Rotorua volcano, Bandama caldera, Gran Canaria, Yellowstone caldera …
Lava domes
Main characteristic: up to 100 meters high and have steep slopes
In lava domes, viscous lava is not very fluid, it cannot easily come out of the vent when extruded. Instead, it piles up on top of the vent forming a large dome-shaped mass of material. Unlike stratovolcanoes like Mount Fuji and shield volcanoes like Pūhāhonu, lava domes are significantly shorter in stature. They form when lava is too viscous to flow a great distance. As the lava dome slowly grows, the outer surface cools and hardens as the lava continues to pile up inside. Typically, these lava domes are found on the flanks of larger compound volcanoes. Lava domes grow primarily from within and can be dangerous because as fresh magma fills their interior, the outer surface breaks down, causing hot rocks and gases to spill from the mountainside.
Known lava domes: Mount Merapi, Soufrière Hills del Caribe volcano, Chaitén lava dome, Lassen peak …
Cinder and slag cones
Main characteristic: small and very common on our planet
This type of volcano does not have horizontal layers, but rather a steep conical hill of tephra or pyroclast (volcanic debris) that accumulates around from the vent. The material from which the cinder cones are made is quite loose. Even those that erupt tend to have less impact than stratovolcanoes, for example. They are usually not more than 350 to 500 meters high . Being less dangerous, the cinder cones are generally created from a single opening, the slopes of which are formed by the fragmented and erupted ash that falls near the chimney or vent.
Known cinder and slag cones: Paricutín in Mexico, Surter I and Surter II from Iceland, Lava Butte …
