Class 11 Geography - GUJARAT
Composition and Structure of Atmosphere
The chapter 'Composition and Structure of Atmosphere' in Class 11 Geography for GSEB explores the layers of gases, water vapor, and dust particles that envelop the Earth. Students learn about the permanent and variable gases, the greenhouse effect, and the vertical division of the atmosphere into the troposphere, stratosphere, mesosphere, thermosphere, and exosphere based on temperature variations. Understanding this chapter is crucial for board exams as it forms the foundational base for climatology, explaining weather phenomena, temperature lapse rates, and why life is sustained only in the lower layers of Earth's atmospheric envelope.
Start Learning FreeKey Concepts
Composition of the Atmosphere
The atmosphere is made up of gases, water vapor, and dust particles. Nitrogen (78%) and Oxygen (21%) make up the bulk, while variable gases like carbon dioxide and ozone play vital roles in heat retention and filtering harmful UV rays.
Structure of the Atmosphere (Vertical Layers)
The atmosphere is divided into five distinct layers based on temperature conditions: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
Troposphere
The lowest and densest layer of the atmosphere where all weather phenomena occur, and temperature decreases with increasing height at a rate of 1°C for every 165 meters (Normal Lapse Rate).
Stratosphere
The layer above the troposphere containing the ozone layer, which absorbs harmful ultraviolet radiation and causes temperatures to increase with altitude.
Normal Lapse Rate
The rate at which atmospheric temperature decreases with an increase in altitude, specifically about 6.5°C per kilometer in the troposphere.
Important Formulas
Board Exam Info
In the Gujarat Board (GSEB) Class 11 Geography exams, this chapter typically carries around 4 to 6 marks. Questions frequently include short notes on the layers of the atmosphere, reasons for temperature decrease in the troposphere, and MCQs regarding the percentage of gases like nitrogen and oxygen.
Frequently Asked Questions
Why does temperature decrease with height in the troposphere?
The troposphere is heated from below by the Earth's surface (terrestrial radiation) rather than directly by the sun, so as you move further away from the heat source (higher altitude), the temperature drops.
What is the difference between weather and climate?
Weather is the day-to-day atmospheric condition of a specific place, while climate is the aggregate of weather conditions and variations averaged over a long period (usually 30 years or more).
Why is the ozone layer important and in which layer is it found?
The ozone layer is found in the stratosphere and is crucial because it absorbs harmful ultraviolet (UV) rays from the sun, protecting life on Earth from skin cancer and other health hazards.
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