If you ask any K-12 teacher what the types of volcanoes are, they will be very quick to answer your question with the 3 volcano system: Shield, Cinder Cone and Composite Cone. There are those who make a very compelling argument however, that this system is far too limiting. “What about Yellowstone Caldera?,” they might ask. Oregon State University makes a very compelling argument that volcanologists would be much better served to classify volcanoes into 6 types instead of 3. Below is their proposed classification system, and the characteristics of each type.
The 6 Proposed Types of Volcanoes and Their Characteristics
These types of volcanoes are considered the largest under the three volcano classification system. Under this system, they are just the largest ones that we would recognize with our eyes. Mount Kilauea and Mauna Loa (which is the largest among active volcanoes on our planet), are two of the most famous examples of these types of volcanoes.
Shield volcanoes are composed almost entirely of basalt, which is a type of volcanic rock that flows very fast in its lava form. This makes these types of volcanoes more shallow and wider, because the lava doesn’t have time to pile up on itself before it cools and solidifies into volcanic rock. They are also some of the gentlest volcanoes in our world, making mesmerizing fountains of lava at the eruption site that aren’t particularly explosive unless there is water present at the site of the eruption.
Stratovolanoes are the most common types of volcanoes on the planet. They tend to erupt with lava that is thicker and slower flowing, enabling it to pile up to great heights. Of course, as the lava piles up, it tends to form a sort of plug that locks in dangerous gasses and pyroclastic materials that build up until the pressure becomes so great that it causes an explosive eruption. This is what makes these such dangerous types of volcanoes to be near during an eruption.
Even greater than the danger of projectiles falling from the summit, is the possible pyroclastic flow, consisting of noxious gasses that are heavier than the air and ashes that flow down the side of the volcano and inexorably smother anything in their path. Mount St. Helens is a famous example of a stratovolcano. An even more famous example is Mount Vesuvius, which caused the destruction of Pompeii.
Monogenetic fields are massive fields that contain hundreds or even thousands of volcanic vents. These types of volcanoes don’t look like volcanoes per se, but they are still volcanic in nature. The supply of magma is not nearly as forceful as it is with other types of volcanoes, so there is never a specific path for the magma chambers like you would see with a more traditional type of volcano. It seems that whenever they gently erupt, the magma finds a new path to the surface.
Believe it or not, America has quite a few of these types of volcanoes. One, called the San Francisco volcanic field has a misleading name. It’s actually in northern Arizona, just north of Flagstaff. There are also quite a few of these fields in Mexico.
The Columbia River Basalt province that covers a large portion of south east Washington is one example of these types of volcanoes. They are remarkable areas on our surface that are covered with dozens of meters thick and hundreds of kilometers long flows of basalt.
Flood basalts are poorly understood, but scientists now think that the thin flowing basalt gets so thick in these areas because new magma is injected into the old, hardened magma that has already erupted and cooled from the site. Over time, the flow becomes thicker and thicker till it reaches epic proportions.
Some scientist feel that the mid-ocean ridges are simple one, enormous, tens of thousands of kilometers long volcano. This is the part under the ocean where our tectonic plates pull apart and squish back together. As they do so, magma escapes from the crust deep under the ocean at the places where these plates clash and pull apart and build ridges of fresh basalt.
While we have never seen one of these eruptions (as they are not one of the easiest places on Earth to get to), we have seen the evidence of them shortly after small earthquakes at the edges of the plates, including super heated water, dead marine life in the area and fresh deposits of basaltic rock.
Rhyolite Caldera Complexes
In the year 83 AD, a massive eruption took place at north eastern Lake Taupo in New Zealand. It was the most massive eruption the world has seen in the past 5,000 years. The cause of this eruption was the incredible pressure building inside the magma vents under the Taupo caldera. The result was a devastating pyroclastic flow that destroyed 20,000 square kilometers of the island, not to mention an astounding ash cloud. Still, this is nothing compared to the devastation that scientists think the Yellowstone caldera is capable of producing.
These “super volcanoes” are more properly classified as rhyolite caldera complexes and they still are not fully understood by science. They don’t even look like volcanoes, but are instead the result of eruptions so massive that the land collapsed completely in on itself over the massive magma chambers that feed them. These eruptions cause calderas that can be hundreds of miles across. Thankfully, these incredibly destructive and fascinating types of volcanoes only erupt on the rarest of occasions.
It’s important to remember of course that all classification systems are subjective. The three volcano system leaves out the most important systems in our world, such as super calderas and the mid-ocean ridges. It would be hard to argue that these systems don’t affect our world.
Some simply classify volcanoes by whether they are dormant, active or reactivated. They authors of Volcanoes of the World, on the other hand, very thoroughly classify 26 types of volcanoes. This may be overkill to anyone but a volcanologist. This six type system seems to pretty well sum up the major types of volcanoes that affect our environment.