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GeographyClass 11Fundamentals Of Physical Geography

Fundamentals Of Physical Geography | Class 11 Geography Notes

By ConceptScroll Team · Published on 17 July 2026 · 4 min read

Fundamentals Of Physical Geography – this guide gives you a concise, exam-ready overview of Fundamentals Of Physical Geography from Class 11 Geography, written by ConceptScroll editors and reviewed against the latest NCERT textbook.

Evolution of Atmosphere and Hydrosphere

Earth's present atmosphere primarily consists of nitrogen and oxygen. Its evolution occurred in three stages. The first stage involved the loss of the primordial atmosphere composed mainly of hydrogen and helium, stripped away by solar winds affecting Earth and other terrestrial planets. The second stage involved volcanic degassing, where gases and water vapor were released from Earth's interior during cooling, forming an early atmosphere rich in water vapor, nitrogen, carbon dioxide, methane, and ammonia but very little free oxygen. Continuous volcanic eruptions contributed to this gaseous envelope. As Earth cooled, water vapor condensed to form rain, which collected in depressions to create oceans within 500 million years of Earth's formation, making oceans about 4,000 million years old. The third stage involved biological modification: photosynthesis by early life forms in oceans produced oxygen, saturating oceans and eventually flooding the atmosphere with oxygen about 2,000 million years ago. This oxygenation was critical for the development of aerobic life.

📊 Diagram: No specific diagram provided, but the process of atmospheric evolution and ocean formation is described.

🔗 Connection: Leads to the final phase of Earth's evolution: the origin of life.

Frequently asked questions

1. Multiple choice questions. (i) Which one of the following figures represents the age of the earth? (a) 4.6 million years (c) 4.6 billion years (b) 13.7 billion years (d) 13.7 trillion years (ii) Which one of the following is not related to the formation or modification of the present atmosphere? (a) Solar winds (c) Degassing (b) Differentiation (d) Photosynthesis (iii) Life on the earth appeared around how many years before the present? (a) 13.7 billion (c) 4.6 billion (b) 3.8 million (d) 3.8 billion

(i) Correct answer: (c) 4.6 billion years Explanation: Scientific evidence from radiometric dating shows that the Earth is approximately 4.6 billion years old.

(ii) Correct answer: (a) Solar winds Explanation: Solar winds are streams of charged particles from the sun and do not directly contribute to the formation or modification of Earth's atmosphere. Differentiation, degassing, and photosynthesis have played roles in atmospheric formation and modification.

(iii) Correct answer: (d) 3.8 billi

2. Answer the following questions in about 30 words. (i) What is meant by the process of differentiation? (ii) What was the nature of the earth surface initially? (iii) What were the gases which initially formed the earth's atmosphere?

(i) Differentiation is the process by which the Earth separated into different layers (core, mantle, crust) based on density during its early molten stage.

(ii) Initially, the Earth's surface was molten and extremely hot, covered by magma and volcanic activity.

(iii) The initial atmosphere was composed mainly of gases like water vapor, carbon dioxide, nitrogen, methane, and ammonia released from volcanic degassing.

3. Answer the following questions in about 150 words. (i) Write an explanatory note on the ‘Big Bang Theory’. (ii) List the stages in the evolution of the earth and explain each stage in brief.

(i) The Big Bang Theory explains the origin of the universe. It states that about 13.7 billion years ago, the universe began from an extremely hot and dense point and has been expanding ever since. This expansion led to the formation of galaxies, stars, and planets including Earth.

(ii) The stages in the evolution of the Earth are:

  • Formation of the Solar System: About 4.6 billion years ago from a nebula.
  • Differentiation: Earth separated into layers (core, mantle, crust).
  • Cooling and solid
Project Work Collect information about the project “Stardust” (website: www.sci.edu/public.html and www.nasm.edu) along the following lines. (i) Which is the agency that has launched this project? (ii) Why are scientists interested in collecting Stardust? (iii) Where from the Stardust is being collected?

(i) The Stardust project was launched by NASA (National Aeronautics and Space Administration).

(ii) Scientists are interested in collecting Stardust because it contains particles from comets and interstellar dust, which provide valuable information about the early solar system and the origin of life.

(iii) Stardust is collected from the coma of comet Wild 2 and from interstellar dust particles in space.

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