NCERT Solutions For Class 11 Geography Chapter 2 The Origin and Evolution of the Earth - 2025-26

1. Multiple Choice Questions.

i. Which one of the following figures represents the age of the earth?

• (a) 4.6 million years
• (b) 13.7 billion years
• (c) 4.6 billion years
• (d) 13.7 trillion years

Answer: (c) 4.6 billion years.

ii. Which one of the following is not related to the formation or modification of the present atmosphere?

• (a) Solar winds
• (b) Differentiation
• (c) Degassing
• (d) Photosynthesis

Answer: (b) Differentiation.

iii. Life on the earth appeared around how many years before the present?

• (a) 13.7 billion
• (b) 3.8 million
• (c) 4.6 billion
• (d) 3.8 billion

Answer: (d) 3.8 billion.

2. Answer the following questions in about 30 words.

i. What is meant by the process of differentiation?

Answer: Differentiation is the process through which the materials inside the earth separated out on the basis of their densities. Heavier materials like iron sank toward the core, and lighter materials moved toward the surface, leading to the formation of different layers like crust, mantle, and core.

ii. What was the nature of the earth surface initially?

Answer: Initially, the earth’s surface was barren, rocky, and hot, with a thin atmosphere mostly composed of hydrogen and helium. There was no water or life, and the planet was in a volatile and unstable state.

iii. What were the gases which initially formed the earth’s atmosphere?

Answer: The initial atmosphere of the earth predominantly consisted of hydrogen and helium. Later, gases like water vapour, nitrogen, carbon dioxide, methane, and ammonia were released from the earth’s interior through volcanic eruptions.

3. Answer the following questions in about 150 words.

i. Write an explanatory note on the ‘Big Bang Theory’.

Answer: The Big Bang Theory is the most widely accepted explanation of the origin of the universe. According to this theory, all matter and energy were once concentrated in a tiny, extremely dense and hot point, known as a "singular atom." About 13.7 billion years ago, this point exploded in a massive event known as the Big Bang, resulting in a rapid expansion of the universe.

As the universe expanded, it began to cool, allowing the formation of atomic particles and later simple atoms. Within three minutes, the first atom formed, and within 300,000 years, the temperature dropped enough for atomic matter to take shape, making the universe transparent.

The expansion continues even today, leading to increasing distance between galaxies. The Big Bang Theory has been supported by observations such as the redshift of light from galaxies, which indicates that the universe is still expanding.

ii. List the stages in the evolution of the earth and explain each stage in brief.

Answer: The evolution of the earth occurred in several stages:

• Formation of the Planet: Earth formed about 4.6 billion years ago from accretion of planetesimals.
• Layering of Earth (Differentiation): As temperature increased, heavier elements like iron sank to form the core, and lighter materials formed the crust and mantle.
• Evolution of Atmosphere and Hydrosphere: The inflow of gases from volcanic activity created a new atmosphere; cooling led to condensation of water vapor and formation of oceans.
• Origin of Life: Life began around 3.8 billion years ago as oceans formed, followed by photosynthetic organisms, which increased oxygen in the atmosphere.

Each stage was critical in making the earth hospitable to life as we know it today.

The Origin and Evolution of the Earth – NCERT Solutions 2025-26

Mastering The Origin and Evolution of the Earth NCERT Solutions for 2025-26 helps students understand how our planet formed and changed over time. Grasping core theories like the Big Bang and the evolution of atmosphere ensures a strong foundation for exam success.

By studying stepwise stages such as lithosphere and hydrosphere formation, you’ll be able to answer even tricky questions in exams. Make sure to revise all NCERT exercises and regularly review chapter-wise solutions and key facts.

Use these structured answers to improve your learning and build conceptual clarity about the development of the earth and life. Consistent revision will boost your confidence and enable high scores in both school and competitive exams!

CBSE Class 11 Geography Chapter-wise NCERT Solutions

CBSE Class 11 Geography Study Materials