CBSE Class 11 Fundamental of Physical Geography: Chapter 2 - The Origin and Evolution of the Earth NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

CBSE Class 11 Fundamental of Physical Geography Chapter 2 introduces the Earth's formation and evolution. This chapter explores the age of our planet and the geological time scale, including eons, periods, eras, and epochs. It details the processes that shaped Earth's atmosphere and discusses the differences between terrestrial and Jovian planets. The early emergence of life and various theories on Earth's origin, such as those by Kant, Laplace, Chamberlain, and Moulton, are examined. A significant focus is placed on the process of differentiation, which resulted in Earth's distinct layered structure. These explanations are designed to enhance exam preparation and deepen the understanding of planetary science.

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Quick info

Board	CBSE
Class	Class 11
Subject	Fundamental of Physical Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 2

Chapter summary

Chapter 2 of Fundamental of Physical Geography focuses on the origin and evolution of the Earth. It covers the estimated age of the Earth, the hierarchical structure of geological time scales, and factors influencing atmospheric development. The chapter also differentiates between inner terrestrial planets and outer gas giants, discusses the timeline of life's emergence, and presents various hypotheses on Earth's formation. Key concepts like planetary differentiation are explained. These NCERT Solutions provide clear answers to all questions, aiding students in grasping these fundamental geological concepts.

Learning outcomes

Understand the estimated age of the Earth.
Differentiate between geological time scales (eons, eras, periods, epochs).
Identify factors influencing the formation of Earth's atmosphere.
Distinguish between terrestrial and Jovian planets.
Explain different theories on the origin of the Earth.
Define and explain the process of planetary differentiation.

Topics covered

Paper topics

Age of the Earth
Geological Time Scale (Eons, Eras, Periods, Epochs)
Formation of the Atmosphere
Terrestrial Planets
Origin of the Earth Theories (Kant, Laplace, Chamberlain, Moulton)
Planetary Differentiation
Appearance of Life on Earth

Important topics

Age of the Earth
Geological Time Scale
Terrestrial Planets
Theories of Earth's Origin
Planetary Differentiation

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Questions and Solutions

Question 1

Multiple choice question: Which one of the following figures represents the age of the earth?

4.6 million years
13.7 billion years
4.6 billion years
13.7 trillion years

Solution: The scientifically accepted age of the Earth is approximately 4.6 billion years. This age has been determined through various radiometric dating techniques applied to rocks and meteorites. Therefore, option (c) is the correct representation of the Earth's age.

Question 2

Multiple choice question: Which one of the following has the longest duration?

Eons
Period
Era
Epoch

Solution: The geological time scale is divided into hierarchical units. The largest and longest divisions are called Eons. Eras are subdivisions of Eons, Periods are subdivisions of Eras, and Epochs are the smallest subdivisions of Periods. Thus, Eons represent the longest duration among the given options.

Question 3

Multiple choice question: Which one of the following is not related to the formation or modification of the present atmosphere?

Solar winds
Differentiation
Degassing
Photosynthesis

Solution: Differentiation is the process by which the Earth's materials separated into layers based on density (core, mantle, crust). While crucial for Earth's internal structure, it is not directly involved in the formation or modification of the atmosphere. Solar winds influenced the early atmosphere, degassing released gases from the Earth's interior, and photosynthesis produced oxygen, all of which are related to atmospheric evolution.

Question 4

Multiple choice question: Which one of the following represents the inner planets?

Planets between the sun and the earth
Planets between the sun and the belt of asteroids
Planets in gaseous state
Planets without satellite(s)

Solution: The inner planets, also known as terrestrial planets, are Mercury, Venus, Earth, and Mars. These planets are located in the inner solar system, between the Sun and the asteroid belt. They are characterized by their rocky composition, unlike the gaseous outer planets.

Question 5

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

13.7 billion
4.6 billion
3.8 million
3.8 billion

Solution: Scientific evidence, primarily from fossil records and geochemical analysis, suggests that the earliest forms of life appeared on Earth approximately 3.8 billion years ago. This was significantly after the Earth's formation (around 4.6 billion years ago).

Question 6 (i)

Why are the terrestrial planets rocky?

Solution: The terrestrial planets (Mercury, Venus, Earth, and Mars) are rocky because they formed in the inner solar system, closer to the Sun. The intense heat from the young Sun evaporated the lighter elements like hydrogen and helium in this region. Consequently, only heavier materials, primarily rock and metals, were left to accrete and form these dense, solid planets.

Question 6 (a)

What is the basic difference in the arguments related to the origin of the earth given by Kant and Laplace?

Solution: Immanuel Kant's original hypothesis proposed that the Earth and other planets formed from a slowly rotating, cold, dusty cloud that gradually condensed due to gravitational attraction. Pierre-Simon Laplace later revised this idea with his nebular hypothesis, suggesting that the planets formed from a hot, rotating gaseous cloud (nebula) associated with the young Sun, which flattened and shed rings of material that eventually coalesced into planets.

Question 6 (b)

What is the basic difference in the arguments related to the origin of the earth given by Chamberlain and Moulton?

Solution: Chamberlain and Moulton proposed the planetesimal hypothesis. They suggested that the Earth originated from the collision of smaller solid bodies called planetesimals. This event was triggered when another star passed close to our Sun, causing tidal forces that pulled out filaments of solar material. These filaments then broke into smaller pieces (planetesimals) that eventually accreted to form the planets.

Question 6 (iii)

What is meant by the process of differentiation?

Solution: Differentiation refers to the process during the Earth's formation when its materials separated into distinct layers based on their density. Heavier elements, like iron and nickel, sank towards the center to form the core, while lighter silicate materials rose to form the mantle and crust. This process resulted in the layered internal structure of the Earth, similar to an onion, comprising the crust, mantle, outer core, and inner core.

Common mistakes

Confusing millions and billions of years for the age of the Earth or life.
Incorrectly ordering or defining geological time scales.
Misunderstanding the characteristics that define terrestrial planets.
Confusing the details of different origin theories (e.g., Kant vs. Laplace).

Revision tips

Memorize the age of the Earth and the approximate time of life's appearance.
Create a table to compare and contrast the different theories of Earth's origin.
Understand the key characteristics that distinguish terrestrial planets.
Focus on the definition and significance of planetary differentiation.
Review the hierarchy of geological time units.

Practice MCQs

Q1. What is the scientifically accepted age of the Earth?

Q2. Which of the following geological time units represents the longest duration?

Q3. Which process is NOT directly related to the formation or modification of the present atmosphere?

Q4. The inner planets, also known as terrestrial planets, are characterized by:

Q5. Approximately when did life first appear on Earth?

Frequently asked questions

What is the estimated age of the Earth according to NCERT?

According to the NCERT solutions for Chapter 2, the age of the Earth is estimated to be 4.6 billion years.

What are the main divisions of the geological time scale mentioned?

The main divisions of the geological time scale discussed are Eons, Eras, Periods, and Epochs, with Eons representing the longest duration.

Why are the inner planets called terrestrial planets?

The inner planets (Mercury, Venus, Earth, Mars) are called terrestrial because they are primarily composed of rock and metal, similar in composition to Earth, and formed in the inner solar system.

What is the process of differentiation in the context of Earth's formation?

Differentiation is the process where the Earth's constituent materials separated into different layers (crust, mantle, core) based on their density during its formation.

Which theories about the origin of the Earth are discussed?

The chapter discusses theories proposed by Immanuel Kant, Laplace, Chamberlain, and Moulton regarding the origin of the Earth.

When did life first appear on Earth?

Life is estimated to have appeared on Earth around 3.8 billion years before the present.

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