Through this article, we have tried to help 9th standard students of CBSE to get some idea on how to write a CBSE Class 9 Social Science Disaster Management Project on Volcanic Eruptions. The topic that we are covering is Volcanic Eruption. Hope you'll enjoy the page -
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My project is on the topic ‘Volcanic Eruptions’. This project is on the disaster taking place due to volcanic activity and the loss of life and property due to this. There are many volcanic activities taking place in the world and the lives being damaged. This is to show formation of volcano, its resources and the type of volcanoes. This activity is happening due to extreme temperature or rise in temperature of earth’s surface.
Volcano, mountain or hill formed by the accumulation of the materials erupted through one or more openings called volcanic vents on the earth’s surface. The word ‘volcano’ can also be used for the vents themselves. Most volcanoes have steep slopes but some can be very gentle slope mountains or flat plateaus or even plains. Most of the world volcanoes are located beneath the sea, formed along the global oceanic ridge system that crisscrosses the deep ocean flow. More than 1,500 above-sea volcanoes have been active during the last ten thousand years, more than 500 of them erupting one or more times during the written history. On an average 50 to 60 above-sea volcanoes are active worldwide in a given year. Volcanic eruptions in populated regions are threat to property, agriculture and people. The danger comes because of the fast flows of explosively erupted materials, lava, falling ash, poisonous gases and volcanic debris flows. In addition to this, volcanic eruption in areas which are not populated would cause pollution anyway which would lead to danger to life.
Volcanoes are formed by magma accumulation which can erupt through volcanic vents (more than one). Vents can be single or multiple openings or a long crack called fissure. It forms deep within the earth usually on the upper part of mantle or within the base of earth’s crust. The solid mantle or crystal rock must be melted under conditions which typically reach at the depth of 80 to 100 kilometers below earth’s surface. Once tiny droplets of magma are formed, it begins to rise as magma is less dense than the solid rock surrounding it. The magma moves upward towards lower pressure regions squeezing into spaces between minerals in the solid rock. As droplets rise, they start to combine themselves hence making larger blobs and together rise towards the surface. Rising magma slowly tends to accumulate in underground storage regions which are also called as magma reservoirs. With each eruption the material erupted adds another layer on the top of the surface. After many eruptions the volcanic material piles up around the vent thus forming a hill or mountain like structure which we recognize as a volcano.
Three types of materials have been identified to have been erupted out of active volcanoes. These materials are:
Lava is the magma that breaks the volcano’s top layer and erupts out of it. Lava flows are continuous, smooth, or they also be ropy or billowy surface called PAHOEHOE flows while AA flows have a jagged surface composed of lose, irregularly shaped lava chunks while PAHOEHOE forms smooth rocks on cooling, AA formed jagged rocks. Lava can also be described using its composition and the type of rock that it forms upon being cooled. Basalt, andesite and rhyolite are all different kidns of rocks which are formed by the cooling of lava. Each type of rock and the lava from which it is formed contains different amounts of silicon dioxide in them.
Tephra is a pyroclastic material which is made of rock fragments created by explosive shattering of sticky magma material. The term ‘pyroclastic’ itself means ‘fire-broken’. Tephra refer to any airborne pyroclastic material regardless of shape and size. The best known tephras are pumice, cinders and volcanic ash. These particles are exploded when the pressure of gases builds up inside the volcano beneath the surface. This pressure is responsible for the explosion of volcanic blocks or bombs and are the largest fragments of tephra. Some are more than 65mm in diameter.
During eruptions of volcanoes, gases are the primary form of steam that are released. All explosive or non-explosive eruptions are accompanied by volcanic gases being released into the earth’s atmosphere. The sudden escape of high pressure volcanic gas from magma is the primary driving force for the explosion of volcanic eruptions. Gases come from the magma or water evaporated by magma’s contact underground.
|Hibok||Philippines||1951||More than 500|
|El Chichon||Mexico||1982||More than 2000|
Volcanoes erupt differently depending upon the composition of the magma which causes the eruption. The differences are the amounts of gas in the magma and the type of vent from which it erupts. The more vicious or stiffer, the lava, the more explosive the eruptive activity. During explosive eruptions, the lava that gets erupted is torn into shreds forming a variety of pyroclastic or fragmental materials depending on the state of lava, physically as well as it depends on the force of explosion. Eruptions can eject a large amount of volcanic material into the atmosphere. Non explosive eruptions make a lot of lava flows and comparatively very little pyroclastic material being released into the air. Following are the two types of eruptions –
Explosive eruptions can eject semisolid as well as liquid lava. Also, they can eject solid fragments of volcanic materials or non-volcanic rocks which have been carried along by the rising magma before eruptions. These eruptions can last for several hours to days and are capable or ejecting a huge amount of pyroclastic material. Some volcanoes produce more energetic eruptions resulting in materials being ejected farther from the vents due to their andesitic and elastic composition. The stiffer lava usually produces more explosive eruptions.
Hawaiian volcanoes are the best examples of non-explosive eruptions as in their case if the eruption is non-explosive, the lava flows are produces instead of explosions. The lava comes out of rifts by the sides of the volcano or vents in a rift. In non-explosive eruptions the ejection of tephra is very rare. Non-explosive eruptions are characterized by ejection of basaltic lava and the type of volcanoes they form are known as shield volcanoes.
Volcanoes come in different shapes and sizes, depending on the magma, the style of eruption and the frequency of their eruption (how often the eruptions take place). The major types of volcanoes roughly in increasing order of size are cinder cones, composite volcanoes, shield volcanoes, calderas and plateaus. Calderas and plateaus are shaped differently. Following is the description of the different types of volcanoes –
Cinder cones and composite volcanoes are similar in their looks. They have cone like shape which is usually famous for volcanoes. Some of these are very beautiful symmetric volcanoes which look like hills or mountains. They are the result of explosive eruptions with a lot of fragmental lava in the eruptions.
Shield volcanoes get their name from their distinctive mountain like shape which have gentle slopes which look like fighting shields used in battles by ancient warriors. They are made up of ballistic lava and can be small or very large in size. Example – Mauna Loa and Kilauea.
It is a round or oval shaped area which is low-lying that forms when the ground collapses during explosive eruptions. The eruption can explode the top off the mountain or eject all of the magma. Calderas can be bigger than the largest shield volcanoes in diameter. Some calderas have hills and mountains rising with them called as resurgent domes that reflect volcanic activity after initial collapse. Some calderas are filled with water. Example – Crater lake in Oregon.
Not all volcanoes look like hills. Some of the largest volcanoes on earth are volcanic plateaus. Volcanic plateaus are extensive, nearly flat-top accumulations of erupted materials. These materials form volcanic plateaus or plains. The basaltic lava flows are called flood or plateau basalts and are erupted from many fissure vents. Volcanic materials might have been far travelled pyroclastic flows or as usual lava flows. Example – Italo is one of the flood basalts. The yellow stone plateau of Wyonung is built of pyroclastic flows.
The magma forming regions of earth and the volcanoes built above them are confined to several zones and special places and are not randomly scattered. While these volcanically active areas have long been known, the scientific reason for their distribution lies in the theory of plate techtonics. According to this the earth’s surface is broken into a dozen or so large solid slabs. These plates are made of rigid upper mantle material as well as crystal material. They are about 50 to 150 km thick and ride from hotter, more free flowing mantle. The two types of locations of volcanoes are –
The three main type of plate boundaries are – divergent, convergent and transform. Divergent boundaries are where non-explosive volcanoes are formed. Most of the world’s above-sea volcanoes are located along the convergent boundaries.
Some volcanoes are located thousands of kilometers from any active plate boundary. They form well defined volcanic chains at times. Hawaiian ridge is one of the best example of such a mid-plate hot-spot vocalnism.
Eruptions pose volcano hazards directly and indirectly to people and property both on ground and in air (flying elements). Pyroclastic flows, lava flows, falling ash and debris flows are direct hazards. Pyroclastic flows are mixtures of gas, hot ash and rock fragments. Their temperature is 850 degree Celsius or higher and have a speed of 250 kmph and above and thus they are deadly. Heavy accumulation of ash can collapse roofs and damage crops especially when aided by rainfall. Indirect hazards are usually non-volcanic effects that follow eruptions or accompany them. Indirect hazards also include large deposits of volcanic materials coming from eruptions. These deposits can form a blanket over grazing lands and farm fields leading to loss of crops, livestock and health of people resulting from them (consumption of crops, usage of livestock). Starvation of people dependent on crops as well as livestock is also one indirect hazard posed by volcanic eruptions. Jet aircraft encounters with airborne volcanic ash during the early 1980s was a volcanic hazard that attracted a lot of attention as indirect hazard resulting from volcanic eruptions. During that time, about 60 airplanes usually commercial jetliners were damaged by such encounters.
It is quite obvious that volcanic eruptions can potentially cause serious human, economic and environmental impacts negatively. However, volcanoes can also be very rich in natural resources. Perhaps the greatest resource that we can get from volcanoes is the land formed by the materials they erupt. Volcanic activity can be credited with some of the most scenic and fertile regions on the planet. Since early twentieth century, harnessing the natural heat of volcanic systems has provided a nearly pollution free source of thermal and electrical energy. For example, the steam from the geysers. Many valuable ore deposits for instance that of lead, nickel, zinc, aluminium, copper, silver and gold are contained in volcanic rocks or in magmatic rocks that form deep routes of volcanoes. Crushed lava rocks, cinders, pumice, and other eruptive products are a source of raw material for building roads, manufacturing, construction and landscaping industries. Hence it can be said that while volcanic eruption is destructive in nature by default, they can prove to be very useful for the human race at the same time.
With the eruption of Eyjafjallajokull, which is a volcano in Iceland, it has been an interesting topic for more than a year. The volcano has erupted for the second time in less than a month, reducing air quality and forcing hundreds of people to flee from rising flood water. This happened in the year 2010. The volcanic ash forced the cancellation of many flights and disrupted air traffic all across Northern Europe stranding thousands of passengers. A volcano in Southern Japan erupted on Feb 1, 2011 sending ash over a wide area and forcing the residents for evacuation. The eruptions destroyed trees and sent bolders hurtling onto roads and smashed hundreds of windows in hotels and offices upto 5 miles away. More than a thousand residents in high risk areas were advised to take shelter in emergency refuse centers amid fears of large amounts of debris, falling ash and landslide of the area.
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