IAS Prelims (GS) preparation 2018
Day # 14 (April 6, 2017)
Topics of the day: Geography 7th NCERT chapter 1 and 2 key points
ENVIRONMENT:
The word Environment is derived from French word Environer which means neighbourhood.
The place, people, things and nature that surround any living organism is called environment.
Environment is our basic life support system.
It provides the air we breath, the water we drink, the food we eat and the land where we live.
It is a combination of natural and human made phenomena.
Biotic is the world of living organisms. e.g. plants and animals.
Abiotic is the world of non living elements. eg - land
LITHOSPHERE:
Lithosphere is the solid crust or the hard top layer of the earth.
It is made up of rocks and minerals and covered by a thin layer of soil.
It is an irregular surface with various landforms such as mountains, plateaus, plains, valleys, etc.
Landforms are found over the continents and also on the ocean floors.
Lithosphere is the domain that provides us forests, grasslands for grazing, land for agriculture and human settlements.
It is also a source of mineral wealth
HYDROSPHERE:
The domain of water is referred to as hydrosphere.
It comprises various sources of water and different types of water bodies like rivers, lakes, seas, oceans, etc.
ATMOSPHERE:
The atmosphere is the thin layer of air that surrounds the earth.
The gravitational force of the earth holds the atmosphere around it.
It protects us from the harmful rays and scorching heat of the sun.
It consists of a number of gases, dust and water vapour.
The changes in the atmosphere produce changes in the weather and climate.
BIOSPHERE:
Plant and animal kingdom together make biosphere or the living world.
It is a narrow zone of the earth where land, water and air interact with each other to support life.
Ecosystem: It is a system formed by the interaction of all living organisms with each other and with the physical and chemical factors of the environment in which they live, all linked by transfer of energy and material.
On 5 June every year the World Environment Day is celebrated.
INTERIOR OF THE EARTH:
CRUST:
The uppermost layer over the earth’s surface is called the crust.
It is the thinnest of all the layers.
It is about 35 km. on the continental masses and only 5 km. on the ocean floors.
The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica andal-alumina).
The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium).
MANTLE:
Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
CORE:
The innermost layer is the core with a radius of about 3500 km.
It is mainly made up of nickel and iron and is called nife (ni– nickel and fe–ferrous i.e. iron).
The central core has very high temperature and pressure.
The crust forms only 0.5 per cent of the volume of the earth, 16 per cent consists of the mantle and 83 per cent makes the core.
The radius of the earth is 6371 km.