NCERT Solutions Class 11 Geography Chapter 2: The Origin and Evolution of the Earth

NCERT Solutions Class 11 Geography Chapter 2: The Origin and Evolution of the Earth– This article includes free NCERT Solutions Class 11 Geography Chapter 2: The Origin and Evolution of the Earth according to the latest CBSE Syllabus 2023-24, and guidelines.

It has been developed by the subject matter experts at GFG, to help the students of Class 11 create a solid conceptual base for NCERT Solutions Class 11 Geography Chapter 2: The Origin and Evolution of the Earth and help them solve questions for exams.

NCERT Solutions Class 11 Geography Chapter 2: The Origin and Evolution of the Earth

Page No: 19

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

Page No: 20

(i) What is meant by the process of differentiation?

Answer:

The process by which earth forming material got separated into different layers is called differentiation.

These layers, progressing from the surface towards the core, include the crust, mantle, outer core, and inner core. Density increases from the crust to the core.

(ii) What was the nature of the earth surface initially?

Answer:

The planet earth initially was a barren, rocky and hot object with a thin atmosphere of hydrogen and helium. This is far from the present day picture of the earth.

Undoubtedly, various events and processes must have occurred to facilitate this transformation from a barren, scorching world to the vibrant planet we know today, abundant with water and possessing an atmosphere conducive to supporting life.

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

Answer:

The Earth’s surface initially consisted predominantly of hydrogen and helium gases. The early atmosphere, rich in hydrogen and helium, is believed to have been eroded away due to the effects of intense solar wind. This phenomenon wasn’t exclusive to Earth; all terrestrial planets likely experienced the loss of their original atmospheres due to solar wind.

As Earth cooled, gases and water vapor were released from its solid interior. Ongoing volcanic activity contributed further to the atmosphere’s development by releasing water vapor and gases. This marked the initial stage of atmosphere formation.

3. Answer the following questions in about 150 words.

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

Answer:

The Big Bang Theory, also known as the expanding universe hypothesis, was supported by Edwin Hubble’s observations in the 1920s, indicating that galaxies are moving away from each other as the universe expands.

About the Big Bang Theory:

• This theory states that all matter in the universe was once concentrated in an infinitesimally small, dense “tiny ball” before a violent explosion, leading to a vast expansion.
• It is widely accepted that this event, the Big Bang, occurred approximately 13.7 billion years ago and continues to drive expansion today.
• Initially, energy was converted into matter during rapid expansion immediately after the Big Bang, with the process slowing over time. Within the first three minutes, the first atoms began to form.
• Approximately 300,000 years after the Big Bang, the temperature had cooled to 4,500 Kelvin, allowing for the emergence of atomic matter and rendering the universe transparent.
• The expansion of the universe entails an increase in the space between galaxies. This concept contrasts with Hoyle’s steady-state theory, which posited that the universe remained roughly the same throughout time. However, mounting evidence in favor of an expanding universe has led the scientific community to predominantly support this perspective.

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

Answer:

Stage I:

During its early phase, Earth was primarily volatile, experiencing increasing internal density and temperature. This led to the segregation of materials based on their densities. Heavier elements, such as iron, migrated towards the planet’s core, while lighter materials moved towards the surface.

Over time, as Earth cooled and contracted, solidification occurred, resulting in the formation of the crust. The formation of the Moon further heated Earth through a massive impact event, facilitating the process of differentiation and the establishment of distinct layers: the crust, mantle, outer core, and inner core.

Stage II:

The initial atmosphere, consisting of hydrogen and helium, is believed to have been stripped away by solar winds. As Earth cooled, gases and water vapor were released from its solid interior, initiating the development of the present-day atmosphere. This early atmosphere comprised water vapor, nitrogen, carbon dioxide, methane, ammonia, and minimal oxygen.

The release of gases from the interior, known as degassing, played a crucial role in this process. Condensation of water vapor occurred as Earth cooled, with carbon dioxide dissolving in rainwater, further cooling the atmosphere and precipitating more rain. Accumulation of rainwater in depressions eventually formed oceans, where life initially thrived. Over time, photosynthesis contributed oxygen to the oceans.

Stage III:

The final phase of Earth’s evolution pertains to the origin and development of life. Life likely originated through chemical reactions that produced complex organic molecules capable of self-replication, transitioning inert matter into living substances.

Conclusion

In this article, we provided free NCERT Solutions for Class 11 Geography Chapter 2: The Origin and Evolution of the Earth, adhering to the latest CBSE syllabus for 2023-24. Developed by subject matter experts at GFG, these solutions aim to assist Class 11 students in building a strong conceptual foundation and preparing for exams.

The Origin and Evolution of the Earth- FAQs

What is the age of the Earth according to scientific estimates?

Scientific estimates suggest that the Earth is approximately 4.6 billion years old.

What is the significance of Eons in geological time scales?

Eons represent the longest duration in geological time scales, encompassing billions of years and providing a broad framework for understanding Earth’s history.

How did the Earth’s early atmosphere evolve?

The Earth’s early atmosphere evolved through processes such as degassing, where gases and water vapor were released from the planet’s interior, and condensation, which led to the formation of oceans and the emergence of complex atmospheric compositions.

What is the Big Bang Theory, and how does it explain the origin of the universe?

The Big Bang Theory proposes that the universe originated from a dense, hot state approximately 13.7 billion years ago. It suggests that all matter in the universe was once concentrated in a small, dense “tiny ball” before a violent explosion led to its vast expansion.

How did life likely originate on Earth?

Life likely originated through chemical reactions that produced complex organic molecules capable of self-replication. Over time, these molecules assembled and evolved, eventually giving rise to the diverse forms of life present on Earth today.