What are the causes of volcanic eruptions? In simple words

Before we delve into the article’s depth, we should understand the definition of volcanoes. Generally,  volcanoes result from magma's eruption into the crust, also known as lava.

In this article, we touch on all the aspects of volcanoes and earthquake formation, differences, and distributions, so let’s start with the interesting ones that will commence from under the Earth.

The creation of volcanoes 

If we want to understand the formation, we should first understand the theory of tectonic plates. 

Why are tectonic plates important? if you asked.

So answer me, where does magma originally form? What are the reasons behind its formation? tell me!

You may answer that magma originated underground from the earth in the magma chamber, and magma is formed due to the subduction of plates.

Structure of the earth's surface

When you observe the image, you see that the earth's inner surfaces are divided into three different categories.

1. Crust (where we are living; the first layer of the earth)
2. Mantle ( the second layer of the Earth where magma is present)
3. Core ( the third and final layer of the Earth, which are responsible for gravity due to their regular rotation)

We talk about these in depth in the other article. Furthermore, now you understand the inner layers of the earth. So, let’s talk in-depth about the structure of the second layer and the concept of tectonic plate movements.

Movements of tectonic plates

As you see in the image, on the crust, you see a layer of the upper mantle, which is cool. After the layer, a part of the mantle appears in the earth in a semi-liquid form known as the asthenosphere. Here, the story of tectonic plates begins.

The presence of the asthenosphere on Earth is responsible for the movement of tectonic plates and the generation of convectional currents. It is the region where magma exists, located approximately 100 km (60 miles) to 700 km (450 miles) beneath the Earth's surface.

Here, you understand how the movement of tectonic plates occurs. These movements of tectonic plates are responsible for volcanic eruptions and earthquakes. 

But a question arises: how? We understand the movement, but what about the push factor that forces magma to flow into volcanic vents and erupt? Here, we should understand the concept of convectional current.

What is convectional current?

In 1919, Sir Arthur Holmes introduced the theory of convection currents as a speculative idea to address the reason behind continental drift theory. Holmes suggested that the movements of tectonic plates floating in the asthenosphere could exert a force through thermal convection currents.  

In the image, you see two arrows: the arrow (cold air) gone down and the red arrow (warm air) gone upside down. According to Holmes, there is a regular rotation in the asthenosphere, causing a consistent flow of air that creates force beneath the earth's surface and results in the movement of tectonic plates.

To understand the concept more clearly, you must watch this video 

How do volcanoes form?

Volcanic eruptions happen due to the inner disturbance of the earth’s crust. How? As we read about the movements of tectonic plates, tell me if something is moving underground by the force so it’s not impacted on the outside. Yes, it’s influenced. That’s why we see the diversity of plains, plateaus, mountains, and huge rocks on the earth. Right!

Despite this, we know that as we dig into the earth to approach the core, the heat waves scorch us as we go deeper. 

Hence, in some weaker points of the crust, these volcanoes exist to exceed the heat and minerals from time to time to maintain balance. If something is heated regularly, it will be blasted if we don’t exceed the heat in time. The pressure cooker is the best example.

 Where do these weaker points exist? 

As you can see in the following map, tectonic plates are divided into several parts. The boundaries of tectonic plates are created due to these types of disturbances. 

Divergent boundary

Creation: When two tectonic plates move in opposite directions from each other called divergent boundaries.

Landforms: through this activity, it created rift valley and mid-oceanic ridges.

Common features: shallow earthquakes, volcanic eruptions, creating a chain of mountains and ridges, and very young lithosphere.

Examples: the best example of a divergent boundary is the Atlantic-ridges which starts from the north pole (87 degrees N) to the south pole of Bourvet Island (54 degrees S) and travels approx 333 km. Thus, it is one of the longest-ridge mountain chains in the earth.

Despite this, the East African Rift (still active), Southeast India Ridge, West Antarctic Rift System etc.

Convergent boundary

Creation: the boundaries are created when a heavy tectonic plate is subducted under a light plate, it is also known as a destructive boundary. The zone where the plate is subducted is called the subduction zone.

Landforms: fault lines, deep ocean trenches, island arcs, folded mountain ranges and volcanoes.

Common features: great earthquakes, tsunamis volcanic eruptions etc.

Examples: Himalayan ranges (India), West Andes mountain (South America), and Mariana Trench (the world’s deepest oceanic trench, located in the western Pacific Ocean near Mariana Island.)

Transform boundary

Transform boundaries neither create nor destroy themselves. Although, like the other two boundaries, transform boundaries never create volcanoes, they can cause disastrous earthquakes.

When two plates are split horizontally from each other, we often feel shallow earthquakes.

Why did it split? Transform boundaries are formed by the shifting movement of the Earth, leading to the powerful Coriolis force.

It’s also known as a transform fault, which is often created in mid-oceanic ridges and near subduction zones.

An example of a transform boundary is the San Andres fault (north America).

Now that we understand the concept of boundaries, what are the possibilities of volcanic mountain forms? Do you know the interesting fact that volcanic mountains exist in different types and shapes based on gases, lava shields, and the composition of magma?

 classification of volcanic mountains

1. Shield volcano: 

These are the world’s largest volcanoes, which are not highly explosive; the lava is very fluid; and they are the home of basaltic rock. Exavolcanoese volcanoes are Hawaiian volcanoes.

1. Composite volcano: 

These volcanoes are explosive, and the lava is thin; hence, it’s slowly moving upward in the vent, which results in stuck gases and heat that push the magma when the heat and pressure are overloaded. Examples are Mt. Fuji (Japan) and Mt. Shasta (California). 

1. Caldera:  

Caldera is the world’s most violently erupted volcano because magma is nearly present under the crust (laccolith). Hence, it destroyed itself or created the great depression where water may collect or the caldera formed a crater of caldera lack. Examples are Lake Tomba (Sumatra) and the Apolaki caldera (the world's largest caldera).

Active dormant and extinct volcanoes

Active volcanoes: active volcanoes are those that have a recent history of eruptions and volcanoes that have erupted for 10,000 years. Examples are Mt. Etna and Mt. Stromboli (Italy). are

Dormant volcanoes: Volcanoes that are currently inactive but have the potential to erupt in the future are known as dormant volcanoes. Examples include Mt. Kalimanzaru (Tanzania, Africa) and Mt. Fuzi (Japan).

Extinct volcanoes: Volcanoes are considered extinct or dead if they have not erupted for 1 million years. An example of an extinct volcano is Mt. Thielsen (Oregon, US).

Sometimes, geographers' predictions go wrong, and a few volcanoes that have been declared dead have often violently erupted in the history of mankind. Mount Vesuvius, located in the Bay of Naples, violently erupted in 79 AD, burying the people who lived around the mountain alive.

A brief introduction to the Ring of Fire

The Ring of Fire is located in the Pacific Ocean; it is the home of 70% of the world’s active volcanoes, and 90% of earthquakes are generated from here.

Tectonic plates such as the Pacific plate, the Indo-Australian plate, the Nazca plate, the Philippines plate, the Eurasian plate, the North American plate, the Cocoas Plate, etc. are located here and their movements created convergent boundaries. 

Hence, we see deep oceanic trenches or volcanic islands and violent earthquakes.

It should be noted that in the Atlantic Ocean, there are mid-ocean ridges, which are the world's biggest chain of rivers and mountains. The ridges are created due to divergent boundaries. 

Final takeaway

So volcanoes form due to the Earth's inner disturbances caused by the movement of tectonic plates and convection currents. And magma is another core factor for volcanoes because the formation of magma and its liquidity are responsible for the different shapes of volcanic mountains.

And the final note is to just read the article carefully by analyzing the images. If you once understand the image and the behind-the-scenes concept, it will be printed in your mind for a lifetime.

To get the article in PDF format, just click here.

Reference

1. Decker, B. B., & Decker, R. W. (2024, June 29). Volcano: Definition, Types, & Facts. Encyclopedia Britannica. https://www.britannica.com/science/volcano

2. Types of volcanoes, British Geological Survey. (2021, June 23). British Geological Survey. https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form/

3. Wei-Haas, M. (2018, January 15). Volcanoes, explained. Environment. https://www.nationalgeographic.com/environment/article/volcanoes

4. Leong, G. C. (1995). Certificate in Physical and Human Geography. Oxford University Press, India. http://books.google.ie/books?id=XhJ4RAAACAAJ&dq=certificate+physial+and+human+geography+gc+leong+ch+3+vulcanism+and+earthquack&hl=&cd=1&source=gbs_api