A volcano can be described as a place situated on the surface of a planet (especially the Earth) or moon where a stream of molten rock, naturally occurring gases and other fragments like ash, cinders, lapilli, blocks and pumice erupt through the body’s crust. The term volcano is believed to have originated from Vulcan-the Roman god of fire. It is claimed that Vulcan used to forge iron on Vulcano which is a volcano situated in the Lipari Islands. This paper discusses the formation, types and the effects of volcanoes.
Formation of Volcanoes
The Earth’s crust is made up of 16 firm plates that maintain a buoyant state on the Earth’s mantle which consists of layers of rock. These plates are always in motion that may cause tension or friction. When two plates are moving in the same direction, one plate may slide on top of the other plate causing what’s called a subduction zone. The lower plate may move further into the mantle. As a result, the rocks lying on the upper plate may get heated up and subsequently melt, forming magma. Magma in essence is molten rock. This magma has the energy to move upward until the Earth’s surface causing an eruption. This movement is also aided by the movement of the plates. When the plates move in opposite direction, they form a rift zone. Thus the magma will come to the surface erupting there. However, there are some eruptions that occur in the hotspots-center of the plates.
It is believed that way beneath the surface of the Earth is so hot, enough to melt rocks forming magma. This magma moves upwards and be deposited in chambers. After some time of this deposition, a portion of the magma may move upwards via the openings in the Earth and eventually erupt. Erupted magma is referred to as lava. Eruptions can range from very explosive to mild. The explosiveness of an eruption will depend on the type of magma. If the magma is light, the lava will just flow out. This type of eruption is more often than not very mild. However, if the magma is heavy and very sticky the pressure build up is so intense that the magma erupts very violently, breaks up into debris referred to as tephra . These types of eruptions are very explosive, and very destructive as discussed later in this paper.
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Types of Volcanoes
Using the former criterion, we can categorize volcanoes into four major types as follows;
- Cinder Cone Volcanoes
Cinder cone volcanoes occur “when particles and blobs of lava are ejected from a volcanic vent”. These pieces fall back around the opening of eruption. When this process repeats itself severally, a cone-shaped figure is formed. A crater may form at the top. Examples of this type of volcanoes are Mt. Ruapehu and Mt. Taranaki.
- Composite Volcanoes
These types have a conduit system that in effect directs the magma from beneath the Earth’s surface up to the surface. Since they have many vents, the lava may erupt through them or through the openings on the sides. The eruptions can reach a height level of more than a kilometer. Examples of composite volcanoes are Mt. rainier, Mt. Fuji and Mt. Saint Helens.
- Shield Volcanoes
These volcanoes resemble a shield when observed from above. They arise when the lava erupted is thin and just flows. This lava may flow for some distance on the surface of the volcano. When this kind of eruption repeats itself many times, they form layers of volcano (shield). Examples of shield volcanoes are Mauna Loa and Mauna Kea.
- Lava Domes
These are formed when small amounts of very thick lava erupt. This lava is too thick to flow a considerable distance. Therefore, the lava just collects around the vent growing the dome with subsequent similar eruptions and internal expansions. A mountain may arise when materials are spilt from the sides of the already formed dome. An example of a lava dome is Mont Pelee.
Volcanoes can also be classified according to their respective activities. Using this criterion, volcanoes can be classified as being active, dormant or extinct. An active volcano is one that has erupted in recent times. This may run from hundreds into thousands of years. A volcano can also be classified as active it’s erupting or showing signs that it may erupt. A dormant volcano is one that has not erupted in the historic time but there’s evidence that it erupted in the past 10000 years. It is also considered that they have the potential to erupt again. An extinct volcano is one that erupted a long time ago and has not exhibited any signs that they may erupt again.
Volcanoes, though they happen naturally, have an impact to those who happen to live around them. As we have seen, a volcano can be very explosive or simply mild. A violent volcano can be very destructive, to the animals and people. On the other hand, other eruptions are welcome. This paper discusses the negative impact of volcanoes and then later, their advantages.
Negative Effects of Volcanoes
A very violent explosion can lead to loss of lives to the community living around the place of the eruption. A classic example of a volcano at its destructive worst occurred in 1883 at Krakatoa. The volcano is said to trigger a tsunami in which 36000 people lost their lives. “When Vesuvius exploded in AD 79, it buried the towns of Pompeii and Herculaneum, killing 16,000 people. Mount Pelee, on the island of Martinique destroyed a town with 30,000 people in 1902”.
Lava flows are usually slow hence many people can easily dodge them. However, this flowing lava will destroy property like buildings and vegetation. Slow and crawling animals will also be swept away; most of them may be killed.
Eruptions more often than not trigger vibrations on the Earth’s surface. This vibration may cause landslides that can also bury or sweep away people, animals, plants and buildings. Lahars can also be formed as a result of these eruptions. Since lahars contain also rocks and move long distances at very high speeds, they destroy almost everything that may be on their path.
The ash thrown in to the atmosphere contains small rock particles that are destructive when they fall back to the surface. They may destroy plants and also cause suffocation to animals and people. According to Bora, volcanic eruptions contain many harmful gases like carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen chloride, hydrogen fluoride, carbon monoxide and metal chlorides that can create a lot of changes in the Earth's atmosphere. Due to the sulfuric acid, we as a result experience acidic rain responsible for cooling the lower atmosphere and increases reflection of radiations increasing the earth’s temperatures as a result.
Positive Effects of Volcanoes
Volcanoes, after the eruptions have stopped, always form some very attractive features. Some features that came about as a result of volcanic activity have become icons, attracting millions of tourists to them. For example, the twin volcanoes; Mauna Loa and Mauna Kea are the tallest volcanoes on Earth and are a great pull to tourists every year. This in essence generates revenue for the local authorities and governments. Having such features not only attracts tourists but also benefits the locals. This is because accessibility to this place is enhanced by developing the infrastructure. This development benefits everyone.
International tourist activities have in the past boosted the relations among countries hence promoting peaceful coexistence among countries. As we have seen, craters may form at the top of a cone volcano. The water accumulated in this crater can act as a habitat to the sea animals. Thus, some volcanoes play a part in wildlife conservation.
Nature is a vital component for human existence. Therefore, people have to learn to coexist with them. Although we cannot prevent volcanoes from happening, we can reduce its destructiveness. This can happen if the people living around a volcano that is showing signs of erupting are evacuated. Also, construction around active volcanoes should be restricted.