Special Topic – UPSC Geography Synopsis
UPSC Prelims Geography Revision | Page 1
Introduction to Physical Geography
Physical Geography deals with the study of the Earth, its structure, landforms, atmosphere, oceans and natural processes. It is one of the most important subjects for UPSC, APPSC, TSPSC and other competitive examinations.
Structure of the Earth
The Earth is divided into three major layers:
- Crust
- Mantle
- Core
Crust
The crust is the outermost layer of the Earth. It is thin and solid. Continental crust is mainly composed of “SIAL” while oceanic crust contains “SIMA”.
Mantle
The mantle lies below the crust. It is composed of semi-molten rocks called magma. Convection currents in the mantle are responsible for plate movements.
Core
The core is the innermost layer of the Earth. It is mainly composed of iron and nickel. The outer core is liquid while the inner core is solid.
Important Discontinuities
- Mohorovicic Discontinuity – Between crust and mantle
- Gutenberg Discontinuity – Between mantle and core
- Lehmann Discontinuity – Between outer core and inner core
Continents and Oceans
Seven Continents
- Asia
- Africa
- North America
- South America
- Europe
- Australia
- Antarctica
Five Oceans
- Pacific Ocean
- Atlantic Ocean
- Indian Ocean
- Southern Ocean
- Arctic Ocean
Asia is the largest continent, while the Pacific Ocean is the largest ocean.
Latitude and Longitude
Latitude and longitude help in locating places on Earth.
Important Latitudes
- Equator – 0°
- Tropic of Cancer – 23½° N
- Tropic of Capricorn – 23½° S
- Arctic Circle – 66½° N
- Antarctic Circle – 66½° S
The Prime Meridian passes through Greenwich in London.
Atmosphere
The atmosphere is the blanket of gases surrounding the Earth. It protects life and regulates temperature.
Composition of Atmosphere
- Nitrogen – 78%
- Oxygen – 21%
- Other gases – 1%
Layers of Atmosphere
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Troposphere
Weather phenomena occur in the troposphere. Temperature decreases with altitude.
Stratosphere
The ozone layer is located in the stratosphere. It protects Earth from harmful ultraviolet rays.
Weather and Climate
Weather refers to short-term atmospheric conditions, while climate refers to long-term weather patterns.
- Temperature
- Humidity
- Rainfall
- Pressure
- Wind
Climate influences agriculture, vegetation and human activities.
Earth Movements
Rotation
The Earth rotates on its axis from west to east. It causes day and night.
Revolution
The Earth revolves around the Sun. It causes seasons.
Important UPSC Facts
- Earth is the third planet from the Sun
- Pacific Ocean is the deepest ocean
- Mount Everest is the highest peak
- Mariana Trench is the deepest trench
- Ozone layer protects life on Earth
Quick Revision Box
- Crust → Outermost layer
- Mantle → Semi-molten rocks
- Core → Iron & Nickel
- Troposphere → Weather layer
- Rotation → Day & Night
- Revolution → Seasons
Mind Map – Physical Geography
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Physical Geography
- Earth Structure
- Atmosphere
- Continents & Oceans
- Latitude & Longitude
- Weather & Climate
- Earth Movements
Shaktimatha Learning
UPSC Geography Synopsis – English Version
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