[Physics Class Notes] on Volcanic Explosions Pdf for Exam

The volcano is the fracture in the surface of planetary mass substances, which permits hot lava, volcanic ash and gases to come out from a magma chamber below the crust. Down the ground, the planet earth is made up of several tectonic plates. The volcanoes of the Earth are the result of the broken crust of 17 vital tectonic plates. They stayed in the hotter and softer layer within the mantle of the Earth. So, volcanoes are often seen where the tectonic plates are separating or intersecting.

Volcano Eruption: What is Volcanic Eruption?

The components within the Earth such as hot lava, rocks, dust when coming out of a volcano in the form of explosion, is known as a volcanic eruption. An explosion can occur from the side branches or the upper part of the volcano. It may be dangerous if vast amounts of rock and volcanic ash start to erupt. These kinds of explosions sometimes take away the lives of many people.

How do Volcanoes erupt?

Down inside the Earth, the temperature is very high. Gradually the extreme heat causes liquefaction of huge stones, and they become a thick liquid substance. The substance is called magma. Eventually, the magma, less in weight than the surrounding rocks, starts its upward motion. It is collected in a magma chamber. In due course, the magma creates pressure and strives to come up through grooves and outlets within the Earth’s crust.

 

As a result, a volcanic eruption has taken place. The magma which has erupted is known as lava. How does the explosion occur? Well, to see the answer, first we need to study the construction of the Earth. The upper portion of the Earth, known as the lithosphere, is the external layer made of upper-crust with a heavy burden. The density of the layer varies from 10km to 100km in mountain areas. They mainly contain silicate rocks.

Reasons for Volcanic Eruptions

Within the ground, the Earth has various layers, which can be divided into multiple groups according to each of their seismology. The classification involves top mantle which varies between 8- 35 km to 410km; transition area extends from 400- 660 km; and then comes the bottom crust which covers an area between 660- 2891 km. Sometimes drastic switch over in conditions occurs from the surface to inner crust. The pressure suddenly increases up to 10000 c. For the rise of temperature, the sticky and melted substances gathered into vast chambers within the Earth’s mantle.

Magma is lighter than the surrounding rocks. So it rises towards the facet. It searches for fissures and vents in the mantle. After it approaches near the crust, the magma erupts from the zenith point of a volcano. Within the layer, the molten rocks are called magma, but after the explosion the magma exits in the form of ash.

After every explosion, rocks, lava and ash are made up within the volcanic cracks. The kind of the blast is absolutely up to the viscosity of the magma. If the lava remains in liquid form, it can cover more distance and release huge volcano shields. When the lava is stiffer, it can create a volcano and can burst. They are called lava domes.

Causes of Volcanic Eruptions in Points

• Inside the Earth’s mantle, the rocks get melted due to high temperature. But its substance stayed within and increased in volume as it transformed into a liquid. The substance is light in weight, as it is less thick than the adjoining rocks. The thin lava then comes up to the crust because they can float easily. If the density of the magma between the area of its creation and the crust is less than the enclosed rocks, the magma gets to the surface and bursts.

• Magmas are formed with andesitic and rhyolitic components. Some dissolved volatiles such as water, sulfur dioxide and carbon dioxide are also present in them. It is proved in the experiments that the amount of liquefied gas in magma at universal pressure is zero, but it hikes with growing force. As magma gradually moves upwards, the solubility of water in it goes down. 

What happens when a Volcano erupts?

Lava that flows from the volcano is so hot that it can destroy cities, livelihoods, plants and animals living around it. The ash, dust and pyroclastics that are emitted from the cinder cones also spoil the environment when they settle down on the ground. If the lava emitted from the volcano is joined by an earthquake or rainfall, it inundates the entire surrounding into the mud. Sometimes, the ash joined by the rainfall damages the surroundings. Apart from these physical threats, volcanoes are associated with health issues like respiratory issues, burns, infectious diseases etc. Volcanoes can also deteriorate rain and water quality, damage crop, and destroy the environment. They could even lead to tsunamis in coastal areas. On the other hand, there are also some positive effects of volcanoes like the creation of new landforms like islands, plateaus, mountains etc, The dust and ash emitted from the volcanoes improve the fertility of the soil and help in improving crop production. When the rocks formed out of lava are weathered, they add a lot of fertility to the soil. Timber can be grown on steep volcanoes and it enhances economic activity.

The excess water is broken up with magma by creating bubbles. The more it comes closer to the surface, the water level decreases and in the channel gas/magma proportion rises. When the volume of the bubbles is about 75%, the magma breaks into pyroclasts and bursts out.