Why do Shield Volcanoes have Weak Eruptions?

What are Shield Volcanoes? What makes Volcanic Eruptions weak? Are Shield Volcanoes less explosive? Which are the Smallest Volcanoes?
why do shield volcanoes have weak eruptions
Photo by March Szeglat

The largest volcanoes on Earth are shield volcanoes, which don’t generate mountains with peaks. They are large volcanoes with gentle slopes and flat shields like those used by warriors. Typical lava flows are used to construct shield volcanoes. They are designed with the idea of recurrent eruptions that take place sporadically over a range of time periods. If you don’t have any idea of what are shield volcanoes then let us discuss this in detail. You will also learn why do shield volcanoes have weak eruptions or why are shield volcanoes less explosive.

1. Why do Shield Volcanoes have Weak Eruptions?

The magma that forms under these volcanoes is called basalt. They are extremely hot and do not contain gas. This shows that the lava does not exit the volcano explosively as compared to other volcanoes which have more acids and are rich in silica. This is the answer to why do shield volcanoes have weak eruptions.

Thus, other volcanoes do not have weak eruptions, they produce a lot of lava in an eruption than any other volcanoes. They are flat at the peak and have a bulging form. When compared to other volcanoes, they are extremely enormous in terms of size and volume. (See Why do people live near Volcanoes?)

2. What makes a Weak Volcanic Eruption?

why do shield volcanoes have weak eruptions 1
Photo by Marc Szeglat

The Hawaiian eruptions have the weakest type of eruption. The following reasons are responsible for what makes a weak volcanic eruption:

  • They have an expansive eruption of the fluid called basalt lava which had low gas content, unlike other volcanoes.
  • The material in the Hawaiian eruptions is less than half of what is found in other eruptive types.
  • They die as the lava begins to penetrate a few of the vents. Central vent eruptions take the form of large lava fountains where that can reach heights of hundreds of meters or more. 

3. Why are Shield Volcanoes less explosive?

The magma that creates a shield is less gluey. Why do shield volcanoes have weak eruptions? It is because these are non-explosives. Shield volcanoes are built in many layers. The less viscous lava spreads out more which makes volcanoes much larger and flatter than stratovolcanoes. Must read why do buildings collapse during an earthquake?

4. Which is the Smallest Volcanoes?

It is located 2 hours south of Manila, in lake Taal. It starts with the journey through the lakeside towns of Talisay and San Agoncillo.

5. What are the Types of Eruptions?

  • Hydrothermal Eruptions,
  • Phreatic Eruptions,
  • Vulcanian Eruption, and
  • Plinian Eruptions.  

6. What are Explosives Eruption?

Explosive eruptions occur where the magma inside the volcano has high gas content and high viscosity, and they are thick and sticky. Underground, magma has very high pressure and has gases involved in it. When it reaches the earth’s surface the gases come out of the solution. The magma is usually thick and sticks for long hours. It requires a great deal of energy to break and explode. (See what is the difference between Oceanic Crust and Continental Crust?)

7. Mt Fuji Eruption: How and When it Happened?

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Photo by Cedric Letsch on Unsplash

Mt Fuji is located in Japan and is said to have the biggest explosion. The last eruption of Fuji ejected tons of tephra into the atmosphere. This Tephra has all solid volcanic material having no lava or volcanic gas. It was preceded by a huge earthquake. It was released during the 1707 eruption of Fuji. It covered almost all the parts of Tokyo and was 62 miles away. There are two types of volcanoes; Old Fuji and new Fuji.

This volcano has caused deaths from disasters and tsunamis. It is known as the Hoei eruption. Moreover, the tephra reduced agricultural productivity in the region, which caused many people to die. (See How Convection Current causes the Lithospheric Plate to move?)

8. What Gases are released after the Eruption?

A lot of gasses from the volcano blow away quickly. They release heavy gases like carbon dioxide and hydrogen sulfide. The commonly released gas is water vapor, carbon dioxide, and sulfur dioxide. These glasses can cause breathing problems for both healthy and unhealthy people. Other gasses are hydrogen chloride, carbon monoxide, and hydrogen fluoride. However, these gasses vary from one eruption to another. Must read What would You expect from an Unstable Air Mass?

9. What creates Volcanic Roar?

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Photo by Jack Ebnet on Unsplash

The sound is created due to the turbulence and friction created by hot gasses which come upward from the volcanic surface vent. These gases have magma particles, ash, and other particles that come through strong inner walls. These sounds can damage ears and can also break the glass. Check out What do Tornadoes Sound like?

The slope of shield volcanoes is gentle, and the proportion at the summit is low. Low viscosities and spreading lava are the causes of their intensity. They come from the lava tunnels and have mild explosions. They resemble mountains but are actually the world’s largest volcanoes. The tectonic plates contain these kinds of volcanoes. All of these points must have answered your question why do shield volcanoes have weak eruptions. (See How are Volcanoes Distributed on the Map?)

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