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Types of Volcanoes

 

One of the reasons that volcanoes are so fascinating is that you could find many different types of volcanoes. The volcanoes can be classified according to their shape, size, dome and even their location. There are other aspects that can also affect the classification of the types of volcanoes found on Earth like the structure of the volcano and if there are any vents or fissure that allow air. Some of those volcanoes are not known for their features but for the type of eruption they will have. Here are some of the volcano types that you will find and how to recognize them.

Fissure Vent

A fissure vent or volcanic fissure is a linear vent on the ground of a volcanic area where lava can erupt from. Usually the lava eruption from a fissure vent will not be an explosive one. The size of the vent is not something that is standard as some can be as small as a few meters wide, but the length can be several kilometers. These types of volcanoes can be very difficult to recognize unless you know that you are standing over it as it is mostly flat. There is no central caldera to these volcanoes and the fissures can be covered up when lava cools down.

Shield Volcano

Shield volcanoes are types of volcanoes which are formed due to several lava flows which eventually give them the shape of a warrior’s shield. These volcanoes are not the tall mountains that you expect to see when you think of a volcano, but rather low profile structures that look more like a small hill than a full mountain. The summit of these volcanoes is usually flat whole the width can be very big. Usually the height of a shield volcano will be just 1/20th of the total volcano’s width.

Lava Dome

A lava dome is a circular volcanic formation which happens due to the viscous lava slow movement. Its shape happens because of the viscosity of the material coming out of the volcano. The domes are very common in volcanic areas and while they are not the awesome show that a volcanic explosion would be it is still something to be admired. Another reason that they form is that there usually is not enough pressure for an massive explosion which means that there could be some sort of vent allowing the gases to escape the structure.

Stratovolcano

A stratovolcano is recognized mostly because of its shape and size. These types of volcanoes tend to be very tall and conical. Their composition will also help you recognize them as they are made of a hardened lava layer, volcanic ash and tephra. Their profile is steep and the lava that shoots out of these types of volcanoes tends to be very viscous and because of that the cooling of the lava will be done quicker than in other volcanoes meaning that the flow will not get too far away. It is not rare for the stratovolcano to be very tall with a lot of them exceeding 2500 meters.

Because of their shape and height a lot of these types of volcanoes have become very famous. One of the most recognized volcanoes that fall under this category is Mount Fuji in Japan. Mount Vesuvius is another highly recognized and extremely famous stratovolcano. Stromboli is another very famous active volcano that falls under the same category. These volcanoes are famous not only because of their shape but also because of the damage they have caused in the past and the possibility that they will cause severe damage in the future as well.

Supervolcano

The supervolcano is out of all types of volcanoes the one that could cause the most damage. Some scientists predict that an eruption of a supervolcano today could in fact end life in the planet due to the massiveness of the eruption. The problem with that prediction is that there have been such eruptions in the past and there will be another one in the future. The last eruption of the Yellowstone supervolcano is believed to have caused the last ice age and that killed several species. If that were to happen today it could mean a world-wide food shortage that would lead to the starvation of those that survived the eruption and the ash.

The supervolcanoes are ranked by the Volcano Eruption Index and they usually fall under the VEI 7 and the VEI 8 Rankings. There have been a total of VEI 8 eruptions in the history of the planet, five of which have taken place in the United States area. There are currently six famous supervolcanoes in the world, and they are the Yellowstone Caldera in the US, The Long Valley Caldera in the US, the Valles Caldera also in the US, Lake Toba in Indonesia, the Taupo Caldera in New Zealand and the Aira Caldera in Japan.

Submarine Volcano

A submarine volcano is a fissure which can be found under water from which there can be an eruption of magma. It has been calculated that up to 75% of the magma output each year comes from these types of volcanoes. Most of these volcanoes are found close to areas where tectonic movement takes place. Those areas are called ocean ridges. Most of these volcanoes are very deep in the ocean, but there are a few of them which can also be found very close to the surface of the water. Because of the depth of some submarine volcanoes they can be very hard to detect.

Subglacial Volcano

A subglacial volcano or glaciovolcano is one that takes place under the surface of the glacier and in some cases under the ice sheet. These types of volcanoes will quickly create a lake due to the fact that the hot lava will melt the ice very fast. The places with the most subglacial volcanoes are Antarctica and Iceland, but they can also be found in Yukon and British Columbia in Canada.

The subglacial volcano is very similar to the submarine volcano because they will both cool the magma quickly creating very similar reactions on the surface. The areas close to a subglacial volcano can be affected by flooding because of the displacement of the water during the eruption and the additional volcanic material which is released. Theoretically an eruption that was massive enough could cause a tsunami to take place.

Mud Volcano

A mud volcano is a very different thing from a regular volcano, but the concept can be similar. These types of volcanoes are also called mud domes and they form by pressure from gases and liquids. The hot water and the mud mix with surface deposits and that is what pushes the surface up. Currently there are 1100 such structures identified, but more are always a possibility especially in subduction zones. Generally these volcanoes will indicate that there may be a petroleum deposit or that there is a volcano nearby.

If a volcano is close to a mud volcano then most of the gas leaving the structure will be Helium, while those that do not have a volcano nearby will emit mostly methane. Current estimates that would take into account the mud volcanoes not found yet, would have the total amount at over 10,000.

 

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Classification Of Volcanoes

 

When studying the volcanoes in the world it is important to understand what the classification of volcanoes is and how it works. There are several factors that go into account when attempting to classify a volcano into a group and that includes things like recent activity, periodicity of eruptions, size, potential impact and others. Though it is not common to hear it volcano eruptions are actually not that rare. More often than not the classification of volcanoes refers to the life cycle and that could define them as active, extinct or dormant. However, a volcano can also be classified by the composition of the structure and that would mean that it can be a shield, conical or stratovolcano. Finally they can also be classified because of its eruption which could be quiet or explosive.

Active Volcanoes

A volcano will be classified as an active volcano if at the present time it is expected to erupt or is erupting already. One of the best examples of this classification of volcanoes would be Kilauea which has been erupting since 1983. There are a total of close to 1,500 of such volcanoes on the planet. Every year somewhere between 50 and 70 volcanoes will erupt.

Dormant Volcanoes

The classification of volcanoes which is called dormant would be a volcano that is not erupting or predicted to erupt in the near future. However, it has done so in recordable history. A dormant volcano is also expected to have an eruption sometime in the future. Sometimes the difference between a dormant volcano and an active volcano can be pretty small. That is because even though a volcano can be dormant for hundreds of years it is still expected to have an eruption in the future.

Mauna Kea is a volcano which is located on Big Island and its last eruption took place 3,500-4,000 years ago. However scientists believe that it will erupt again. What makes that volcano dormant is that currently there is no prediction as to when that eruption could take place. A dormant volcano could be very dangerous because people in the surrounding areas are usually not prepared and complacent leaving close to the mountain. Before its eruption in 1980, Mount St. Helens was dormant.

Extinct Volcanoes

An extinct volcano is a volcano that no one expects will ever have another eruption. One such volcano is also located on Hawaii’s Big Island and its name is Kohala. The last time that Kohala erupted was close to 60,000 years ago. As of now scientists do not believe that volcano will ever be active again. Keep in mind that this classification of volcanoes that are extinct is not necessarily definitive as some have gone through what is called rejuvenation.

Type Classifications

Classification of volcanoes can also be done because of the type of composition and structure of the volcano. A shield volcano is dome shaped and low. These volcanoes are mountains that have been shaped by the flows and can cover larger areas. The simplest form of volcanoes would be the cinder cone type. These volcanoes have erupted from one single vent and a bowl shaped crater will be found in the summit. The most common type of volcano is the strato or composite. These are tall mountains that have steep sides and which have alternated magma and layers of rock.

Eruption Classification

There are two types of classification of volcanoes based on eruption and these are central or explosive and fissure or quiet. An explosive eruption happens because of a buildup of gas under very viscous slow flowing and thick magma. These types of eruption are very violent and rapid; more often they will spew volcanic material, lava and ash onto a large area. A fissure or a quiet eruption will emit a lot of lava from a fracture or fissure. Because lava would usually have a low viscosity, the gas can easily escape.

Samples Of Volcanoes

There are several places in the world which can demonstrate the classification of volcanoes but most active volcanoes will be found in the Pacific Ring of Fire. There are, however, volcanoes not located in the Pacific which are active; some of them include Etna and Vesuvius, Mount Pinatubo and Stromboli.

Classification of volcanoes that are dormant will include a lot of the volcanoes still found in the Ring of Fire and other places nearby. One example would be Mount St. Helens previous to its 1980 eruption. Before a dormant volcano is about to erupt it is usually proceeded by small tremors and earthquakes.

Finally when you are looking at extinct volcanoes you can look at the ones in the Eiffel district in West Germany as well as several volcanoes in USA. There are two volcanoes in Northern Ireland which are also extinct volcanoes and those are Skye and Mull.

 

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