Power of Nature: “Volcanoes”
Whenever we think of the destructive forces of nature, one of the things that strike our mind is a “Volcano”. It is truly amazing how a beautiful mountain can suddenly become so violent, spewing out fire, like a dragon, destructing everything in its path. Villages lying next to volcanoes are in high danger as the temperature of the lava could kill humans instantly. Let us first understand what is a volcano, next we will move onto the formation, types of volcanoes, different terms used and everything there is to know about these beasts.
What are Volcanoes?
To understand what volcanoes are, we have to look deep into the earth. The earth consists of three layers, namely the crust, mantle and core. The crust is the ground on which we walk. It is roughly 64 kms thick and consists of dust, stone, gravel, and all other elements (metals and non-metals). Next comes the “Mantle”; it is the thickest layer of the earth. It is very hot, and under immense pressure. Due to this the material is present in a semi solid form even though the temperature is more than the melting points of the materials. The molten part of the mantle is known as “Magma”. The third layer is the centre most layer of the earth and is called the core of the earth. The core is the hottest part of the earth (around 60000 Celsius) and is made up of solid Iron. A volcano is a link that exposes the mantle onto the surface of the crust. The most general perception of a volcano is a mountain with a hole on its flattened top which spews out magma and large ash clouds into the air. But volcanoes can occur in any form. For example certain oceanic ridges present deep in the oceans can expose “deep sea vents” which release magma.
Formation of Volcanoes
Volcanoes usually form at places where “tectonic plates” meet.The crust is present in the form of plate like structures called tectonic plates. These plates move as per the movement of the mantle layer, drifting over them. Whenever two tectonic plates meet, they can form in two primary ways. In one situation, the tectonic plates tend to move away from each other, leaving a gap in between them. This gap is filled, when the solid part of the mantle forming a new crust. Therefore, the crust becomes thinner in this region and reduces some amount of pressure which melts the mantle forming “magma”. This tectonic formation causes oceanic and continental ridges. The boundaries between such tectonic plates are known as “Divergent Plate Boundaries”. This type of formation is called “Spreading Centre Volcanism”.
The next type is the opposite of its counterpart. These types of volcanoes are formed when tectonic plates converge with each other. A typical converging plate is formed when an oceanic plate converges with a continental plate. The oceanic plate goes below the continental plate. As expected they are formed near the shores. Deep trenches are formed due convergent tectonic plates. This process is called “Subduction”. The water from the ocean lowers the melting point of the mantle wedge below the continental tectonic plate. This leads to the formation of magma. This magma mostly settles down at the bottom but if it reaches the surface of the ocean, it forms a volcano. This type of formation is called the “Subduction Zone Volcanism”.
The magma that emerges from in between the tectonic plates cool down and form “plumes” (the conical shape). The molten rock inside (magma) applies immense pressure on the rocks lying above them since they have lower density. This is similar to a helium balloon rising and pushing through the air above it. This pressure causes the rocks above to melt and causes a vent into the plume to exit, causing the volcano. When the magma exits, it is called lava (flowing magma). A typical volcano will have the following parts:
1. Summit crater – the “mouth” of the volcano (where eruption takes place).
Different types of Volcanoes
Based on the frequency of eruption, volcanoes can be classified as active, dormant and extinct. The names explain it all. The active volcanoes are the volcanoes which erupt at a regulated interval. This may be from once a year to once in a decade.
The extinct volcanoes are the ones which have not been active for a long time. This occurs when the magma supply of the volcano runs out.
A dormant volcano is an unpredictable volcano. It is in the border of the extinct and active volcanoes. They have magma supply and have not erupted for a lengthy period of time. Dormant volcanoes prove to be dangerous because of their unpredictable nature.
Dangers of a Volcano
The hot flowing lava of the volcanoes are not its only danger, but the volcanic ash containing dense gases like sulphur dioxide, carbon dioxide and rock ash. This blocks the sunlight in nearby areas and can causes respiratory problems. The volcanic ash is not detectable by flight radars, and most often aircrafts fly into these ash clouds. This causes navigational problems. The ash can also form layers on the cockpit window and melt due to frictional heat. Therefore to avoid these ash clouds, instructions are given by the ground staff reporting the pilots of nearby volcanic activity.
Volcanoes will exist wherever there is a movable crust and molten material below it. This is the property of many of the planets which have hot cores. One of the most famous inter planetary volcanoes is “Olympus Mons”, located on mars.
Through volcanoes we understand the raw power of our nature. The ability to destroy whole villages in a short span of time leaving no trace of the crime, gives volcanoes its immortal and god like status in some tribes, or an expression of anger of the gods. Certain philosophers believed that the earth cries through volcanoes and the lava are the tears. Whatever one may believe about volcanoes, no one can deny its power. Very few people dare to go near a volcano, even a dormant one.