KERALA PSC / PHYSICAL GEOGRAPHY / VOLCANOES / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

 

KERALA PSC / PHYSICAL GEOGRAPHY / VOLCANOES / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

KERALA PSC / PHYSICAL GEOGRAPHY / VOLCANOES / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE

·      A volcano is formed when the molten magma in the earth’s interior escapes through the crust by vents and fissures accompanied by steam gases (hydrogen sulphide, Sulphur dioxide, hydrogen chloride, carbon dioxide etc) and solid materials.

·      The molten rock material is the most common form of volcanic matter ejected during volcanic activity. This material is called Magma. Upon reaching the surface of the earth, it is called Lava.

·      Volcanic activity is an important process of construction on the earth’s surface.

·      Crater is a funnel shaped depression having a circular plan and a neck at the centre. Craters are formed by explosion or subsidence.

·      Sometimes, the volcanic material may not be able to reach the surface and it may get deposited in the layers of the crustal rocks. This type of activity is called intrusive volcanic activity.

·      There are two main types lavas – Basic lavas and Acid lavas

·      Basic Lavas: These are the hottest lavas about 1000ºC and are highly fluid. They are dark coloured like basalt, rich in iron and magnesium but poor in silica. Due to their high fluidity, they flow readily with a speed 10 to 30 miles per hour. The resultant volcano is gently sloping with a wide diameter and forms a flattened shield or dome.

·      Acid Lavas: These lavas are highly viscous with a high melting point. They are light coloured of low density and have a high percentage of silica. They flow slowly and the resultant cone is steep sided. Sometimes they lavas are so viscous that they form a spine or plug, at a crater. Eg: Pelee in Martinique.

·      Circular deposit of lava may remain higher than the areas surrounding it. Such a feature is called a volcanic plug.

·      Concave Saucer shaped deposits of lava in the crustal rocks are called lopoliths.

·      There are three types of volcanoes – active, dormant and extinct.

·      An active volcano erupts occasionally. Eg: Mount Stromboli in Italy, Barren Islands in India (The only active volcano in India), Mt.Etna in Sicily and Cotopaxi in Ecuador

·       Mt. Stromboli whose frequent eruptions that resulted in more like a summit glow, have earned it a crown title ‘Light house of the Mediterranean’

·      A dormant volcano has not been seen to erupt, but it shows evidence of recent activity.

·      Mt. Vesuvius and Mt. Krakatau are examples of dormant volcano

·      An extinct volcano shows no sign of life. Eg: Mt. Kilimanjaro

·      Fumaroles are fissures in the ground of volcanic areas through which gases including nitrogen, ammonia, carbon monoxide and methane are given off.

·      The Pacific belt is known as the Ring of fire because of the largest number of active volcanoes along the coasts of America and Asia on the ocean.

·      Batholiths are a large mass of magma which often forms the root of a mountain and is made up of granite

·      Famous volcanoes of the world: Cotopaxi (Ecuador), Mt. Kilimanjaro (Tanzania), Mt. Etna (Italy), Mt. Vesuvius (Italy), Mt. Popa (Myanmar), Mauna Lao, Mt. Kenya, Mt. Stromboli (Italy)

·      The volcanic islands of Hawai in the mid pacific, the famous hot water geycers of the Yellow Stone region of North America are examples of inplate volcanoes.

·      Surtsey, is an island born from a series of volcanic explosions from deep within the earth’s core culminated in the creation of a barren crest of rock that jutted from the Atlantic Ocean.

·      Geysers and Hot springs are natural sources of hot water. A Geyser through up jet of hot water alternating with steem at regular intervals. They are associated with volcanic or thermal regions.

·      Springs are sources of water from which the water flows out on its own. Some of the spring provides hot water and they are called hot spring or thermal springs

·      In some regions the hot spring are found in large numbers, they are harnessed to produce energy. This energy is called geothermal energy. Eg: Manikaran in Kulu region

KERALA PSC / PHYSICAL GEOGRAPHY / VOLCANOES / NOTES / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE