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UPSC Prelims Answer Key 2021 with Solution. UPSC Prelims 2021 Question Paper with Answer Keys, General studies Paper 1

https://www.legacyias.com/upsc-prelims-2021-question-paper-with-answer-keys-general-studies-paper-1/

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#upsc #upscaspirants #upscexam2021 (at Lucknow, Uttar Pradesh) https://www.instagram.com/p/COzqPV4prTG/?igshid=11qdgdsvhzo25

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Cyclones are large scale air mass that rotates around a strong center of low atmospheric pressure. Based on the geographical location, the Cyclones are of two types namely Tropical Cyclones and Temperate Cyclones (Extra Tropical Cyclones). TROPICAL CYCLONES Tropical Cyclones are violent storms that originate over the seas in the Low pressure belt of the tropical areas and move eastward over to the coastal areas. They bring about large scale destruction caused by violent winds, very heavy rainfall and storm surges which make them as one of the most devastating natural calamities. They are known as Cyclones in the Indian Ocean, Hurricanes in the Atlantic, Typhoons in the Western Pacific and South China Sea, and Willy-willies in the Western Australia. They originate only over the seas because of the need of continuous moisture to energize the Cyclones regularly. This is why they dissipate once reaching the land. They are violent because of the energy coming from the condensation process in cumulonimbus clouds surrounding the Cyclones. They move from east to west because they are facilitated by the Trade wind. TEMPERATE CYCLONE This system develops in the mid and high latitude (around 600 latitudes) along the polar front (boundary between the warm air and cold air). As the polar front develops over entire polar frontal system, this cyclone affects a much larger area of around 2000 km. Also it develops over land and sea both as far as there is frontal system. It moves from west to east due to the influence of Westerlies. When the pressure drops along the front, the warm air moves northwards and the cold air move towards south setting in motion for anticlockwise cyclonic circulation. The warm air glides over the cold air and a sequence of clouds appear over the sky ahead of the warm front and cause precipitation. The cold front approaches the warm air from behind and pushes the warm air up. As a result, cumulus clouds develop along the cold front. The cold front moves faster than the warm front ultimately overtaking the warm front. The warm air is completely lifted up and the front is occluded and the cyclone dissipates.

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Atmospheric Pressure

Atmospheric pressure is the weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere. Therefore, at a place, if the air is dense for instance near the Earth’s surface (due to Gravity), the atmospheric pressure will be more. It is expressed in atm (Atmosphere), mb (millibar) and Pa (Pascal). It is measured with the help of a mercury barometer or the aneroid barometer. At sea level, the average atmospheric pressure is 1 atm or 1,013.2 mb or 1,013.2 h Pa (kilo Pascal). VARIATIONS OF ATMOSPHERIC PRESSURE As the Pressure depends on the number of air molecules present at any place, it varies both vertically as well as horizontally. This variation of the Atmospheric Pressure has been playing a very important role in Weather and Climate. Its variation is the main cause of air motion/ wind. VERTICAL VARIATION The pressure decreases with height because air gets thinner. The average decrease is about 1 mb per each 10m increase in elevation, subject to other factors such as Temperature, local topography, closeness to the sea, etc. Therefore, if the surface Atmospheric Pressure at any place is 1,000 mb, then the Pressure at 1 km above the surface will be (1000 – 100) mb i.e. 900mb. Despite high vertical pressure gradient, there is weak upward wind because the pressure gradient gets weakened by the Gravitational force. HORIZONTAL VARIATION The horizontal variation of the Pressure depends on the differential heating (insolation) of the surface which causes the differential air volumes. These variations are highly significant in terms of wind direction and speed. Though the direction and speed depend also on Frictional force and Coriolis force. Horizontal distribution of pressure is studied by drawing isobars (lines connecting places having equal pressure) at constant levels.

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A volcano is a place where gases, ashes and/ or molten rock material ‘ lava’ escape to the ground through fissures and faults, etc. It is from asthenosphere that the molten rock materials find their way to the surface. If the materials remain below the surface, it is called magma. If the materials find a way to come out on the surface, it is called lava. These magma and lava form different types of structure called Volcanic Landforms. These landforms can be extrusive, or intrusive. EXTRUSIVE LANDFORMS The structure formed by Lava and other materials such as Ashes and Pyroclastic materials is called extrusive landforms. These include Shield Volcano, Composite Volcano, Caldera, and Flood Basalt Province, etc. The Shield Volcanoes are formed if the lava has low viscosity. Hence, they are not steep. After the Basalt province, the shield volcanoes are the largest of all the volcanoes. Examples are Mauna Loa, Hawaiian Islands, USA, and Galapagos Islands. Composite Volcanoes form in many years after multiple eruptions. These volcanoes contain pyroclastic materials and ashes other than the thick and highly viscous magmatic lava. Examples are Mount Kilimanjaro and Mount St. Helens. When a large amount of magma erupts in a short time the rock underlying the magma collapses. This result in depressions, called Caldera. These are the most explosive in nature. Highly fluid lava, made of basalt when erupting on the surface, it forms a flood basaltic province. The Deccan Trap is one such example. INTRUSIVE LANDFORMS When the magma remains within the lithosphere, cools over there and forms different types of structure, are called intrusive landforms. These include Lacoliths, Phacoliths, Lapoliths, Sills, Dykes, and Batholiths, etc. Large bodies of magmatic material that cools in the deeper depth of the crust and develop in the form of large domes are Batholiths. These are the cooled portion of magma chambers. Lacoliths are large dome-shaped intrusive bodies with a level base and connected by a pipe-like conduit from below. When the lava makes its way through cracks and the fissure developed in the land, it solidifies almost perpendicular to the ground. It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes. These are the most commonly found intrusive forms in the western Maharashtra area. Sills, unlike dykes, are thin horizontal intrusive igneous landform. Lapoliths are intrusive volcanic landforms having saucer shape and concave to the sky.

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Earthquake Waves

PRIMARY WAVES/P-WAVES P-waves moves longitudinally i.e. the propagation and vibration are in a same direction similar to the sound waves. They are the fastest of all the earthquake waves. They travel through gaseous, liquid and solid materials. SECONDARY WAVES/S-WAVES S-waves are second to reach at the surface after P-waves. As they can travel only through solid materials of the Earth, they cannot pass through Earth’s outer core, therefore their shadow zone is broader than that of P-waves. This reveals that the outer core of the Earth is not in solid form. S-waves propagate transversally i.e. the direction of propagation and the direction of vibration is perpendicular to each other. SURFACE WAVES Surface waves are generated when the body waves interact with the surface rocks. As they move along the surface and the direction of the vibration is perpendicular to the propagation, these waves are considered as the most damaging one. THE EMERGENCE OF SHADOW ZONE Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’. Seismographs located at any distance within 105° from the epicenter, recorded the arrival of both P and S-waves. Seismographs located beyond 145° from the epi-centre record the arrival of P-waves, but not that of S-waves. Thus, a zone between 105° and 145° from epicenter was identified as the shadow zone for both the types of waves.

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UPSC announces Geologist and Geo-Scientist Exam 2021

UPSC Geologist Exam 2021 - Union Public Service Commission (UPSC) has issued exam notification of Combined Geo-Scientist and Geologist Examination 2021. Online applications are invited from the eligible candidates for UPSC Geologist Exam 2021 and Geo-Scientist Exam 2021

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UPSC CDS I 2021 Notification, Exam Date

UPSC CDS I 2021: Union Public Service Commission (UPSC) has released the notification for the Combined Defense Services Examination I (CDS Exam I) 2021. UPSC CDS Exam 2021 (I) is held for recruiting candidates for the course conducted by Indian Military Academy, Indian Naval Academy, Air Force Academy and Officers Training Academy. The CDS exam is conducted twice in a year.