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Volcanic Eruptions

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Sneha Biju

on 20 June 2014

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Transcript of Volcanic Eruptions

The Earth's crust is made up of huge slabs called plates, which fit together
like a jigsaw puzzle. These plates sometimes move. The friction causes earthquakes and volcanic eruptions near the edges of the plates. The theory that explains this process is called plate tectonics.In a volcanic eruption, hot lava spews out from beneath the Earth's crust up to the Earth's surface. This lava is actually hot melted rock called magma. Just underneath the Earth's crust is a layer called the mantle, which is made of up plates that are always moving and shifting. Sometimes the plates separate. That creates heat and causes the mantle to melt into magma. The magma comes up through the crack between the plates. It spreads out, cools down, and becomes rock again. The solid magma stays beneath the Earth's surface.

A volcano is basically a mountain or hill, having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the earth's crust.When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash and floods. Volcano eruptions have been known to knock down entire forests. An erupting volcano can trigger tsunamis, flash floods, earthquakes, mud flows and rockfalls.

What are volcanoes?

Volcanoes are formed when magma from within the Earth's upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger. While the gases get thrown into the air, the magma and ash cool down forming distinctive volcanic landforms.To understand in detail, the process of formation of volcanoes, we have to understand what lies beneath the surface of the Earth.

How are volcanoes formed?
What are the different types of volcanoes?

There are many great volcanic eruptions,in the past and in the present.But one of the greatest of them all is the eruption of Mount Vesuvius in Pompeii,Italy.Basically,Pompeii was a place where roman generals or soldiers including rich and posh people and middle classed villagers lived in.They used to do very bad sins as you will find out in your quiz song ,and many believe that is why this tragic catastrophe happened.The people weren’t warned although some knew but didn’t have much time to flee.The whole city was covered by lava and was coated with ashes.Even if you visit today,you can still walk down the streets and see the remains of houses,palaces,people standing in a pose,ancient objects and rock-hard resources around.Tears will fill your eyes when you see mothers hugging her children ,many trying to protect themselves and trying to run away but getting caught in the hot molten lava.

Greatest Volcanic Eruptions
Scientists have categorized volcanoes into three main categories: active, dormant, and extinct. An active volcano is one which has recently erupted and there is a possibility that it may erupt soon. A dormant volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future. An extinct volcano is one which has erupted thousands of years ago and there’s no possibility
What are the different stages of a volcano?
Cinder Cones
Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent
Composite Volcanoes
Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris. Mt. Rainier and Mount St. Helens are examples of this type of volcano

Shield Volcanoes
Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Basalt lava flows from these volcanoes are called flood basalts. The volcanoes that formed the basalt of the Columbia Plateau were shield volcanoes.

Lava Volcanoes
Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent. The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.

Any Questions?
Please raise your hand
Our Reflection:

How and Why do volcanoes erupt?
First,form a circle
A volunteer will
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