NCERT Notes Earth Origin and Evolution [Geography Notes For UPSC]
NCERT Notes Earth Origin and Evolution [Geography Notes For UPSC]
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NCERT Notes Earth Origin and Evolution Geography Notes For UPSC

NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about the Geography syllabus for IAS exam as an assimilating discipline as a science of spatial characteristics and Divisions of geography and the significance of physical geography. NCERT Notes Earth Origin and Evolution Geography Notes For UPSC

The origin and evolution of the earth

Early Theories

Nebular Hypothesis

  • Immanuel Kant, a German philosopher gave this theory.
  • In 1796, a mathematician Pierre-Simon Laplace reexamined it.
  • According to this hypothesis, the planets were molded out of a
    cloud of material associated with a young Sun, which was
    rotating slowly.

Binary theories

  • As per these theories, the sun had a companion.

Revised Nebular Hypothesis

  • Revised Nebular Hypothesis was propounded by Carl Weizascar in Germany and Otto Schmidt in Russia.
  • They regarded that a solar nebula surrounded the sun and that the
    nebula comprised of chiefly hydrogen, helium and something called dust.
  • The collision of particles and the friction caused a disk-shaped
    cloud to be formed and then the planets were created via the accretion
    process.

Modern theories

Big Bang Theory

  • Alternatively called the expanding universe hypothesis.
  • As per this theory, in the beginning, all matter or substance
    forming this universe existed at one place as a tiny ball. This tiny
    ball had an extremely small volume, infinite density and temperature.
  • At the Big Bang, this ball blasted fiercely and forcefully and
    started a substantial process of expansion which continues to this day.
  • Now it is accepted that this event took place 13.7 billion years ago.

Origin of Earth

Formation of Planets

The following are regarded as the stages in the planets’ development:

  • The stars are localised gas lumps inside a nebula.
  • A core to the gas cloud as well as a spinning disc of dust and gas are created because of the gravitational force within the lumps.
  • After this, the cloud of gas condenses and the matter over the core is changed into tiny rounded objects.
  • These small round objects develop into what are called planetesimals by a cohesion process.
  • The smaller objects start forming larger bodies by colliding with one another and they stick together because of gravitational force.
  • In the last stage, these large number of small planetesimals aggregate to develop into a smaller number of large bodies called planets. NCERT Notes Earth Origin Evolution

Lightyear

  • It is a unit of astronomical distance which is equal to the distance light travels in one year.
  • A light-year is a measure of distance and not of time.
  • Light travels at a speed of 300,000 km/second. binary theories in geography

Solar system

  • Solar system consists of eight planets.
  • Mercury, Venus, Earth, Mars, Jupiter, Uranus, Saturn and Neptune.
  • The inner planets are Mercury, Venus, Earth, and Mars.
  • After an asteroid belt come the outer planets, Jupiter, Saturn, Uranus, and Neptune.

The Moon

  • The moon is the only natural satellite of the earth.

Evolution of the Earth

  • The age of Earth is approximately one-third of the age of the universe.
  • Earth formed around 4.54 billion years ago by accretion from the solar nebula.

Lithosphere, Atmosphere, and Hydrosphere of the Earth

  • Lithosphere: The firm outer part of the earth, comprising of the crust and upper mantle.
  • Atmosphere: A layer of gases encircling a planet that is seized in place by the gravity of that body.
  • Hydrosphere: It is the collective mass of water found on, under, and above the surface of the earth.
  • The first stage of the evolution of Lithosphere, Atmosphere, and Hydrosphere is marked by the loss of the primordial atmosphere.
  • In the second stage, the hot interior of the earth contributed to the evolution of the atmosphere.
  • Finally, the composition of the atmosphere was modified by the living world through the process of photosynthesis.
  • The present composition of earth’s atmosphere is chiefly contributed by nitrogen and oxygen. binary theories in geography NCERT Notes Earth Origin Evolution

Geological Scale

ncert

The Beginning: The Big Bang Theory

The story of our Earth begins with the Big Bang, a massive explosion that occurred around 13.8 billion years ago. This explosion led to the formation of the universe. Imagine a tiny dot, smaller than a pinhead, suddenly expanding into the vast universe we know today. This marked the birth of time, space, and all the matter in the universe.

Formation of the Solar System

Fast forward a few billion years, and we arrive at the formation of our solar system. About 4.6 billion years ago, a giant cloud of gas and dust, known as the solar nebula, started to collapse under its own gravity. As it collapsed, it began to spin, forming a flat disk with the Sun at its center.

The remaining material in this disk started to clump together, forming the planets, moons, asteroids, and other celestial bodies. Our Earth was one of these clumps, initially a hot, molten mass.

The Cooling of Earth

Over time, Earth began to cool. As it cooled, a solid crust formed on its surface. This crust was constantly reshaped by volcanic activity and the impacts of celestial objects like meteorites. Imagine a hot ball of lava slowly hardening into a solid rock, with constant eruptions and bombardments creating a dynamic and ever-changing surface.

Formation of the Atmosphere and Oceans

As volcanic eruptions released gases from Earth’s interior, our planet’s early atmosphere began to form. This atmosphere was vastly different from what we breathe today, composed mainly of water vapor, carbon dioxide, methane, and ammonia.

Eventually, Earth cooled enough for water vapor to condense and fall as rain, filling the planet’s basins and forming the first oceans. These oceans played a crucial role in the development of life, acting as a cradle for the first simple organisms.

The Origin of Life

Life on Earth began in the oceans around 3.5 billion years ago with simple, single-celled organisms. These microorganisms gradually evolved into more complex forms, leading to the rich diversity of life we see today. Think of it as a tiny seed sprouting and eventually growing into a vast and varied forest.

Continental Drift and Plate Tectonics

One of the most fascinating aspects of Earth’s history is the movement of its continents. This concept, known as continental drift, was proposed by Alfred Wegener in the early 20th century. According to this theory, Earth’s continents were once part of a supercontinent called Pangaea, which eventually broke apart and drifted to their current positions.

This movement is driven by plate tectonics, where Earth’s outer shell (the lithosphere) is divided into several plates that float on the semi-fluid mantle below. These plates constantly move, causing earthquakes, volcanic activity, and the formation of mountains.

Human Evolution

Humans are a relatively recent addition to Earth’s story. The first human-like beings, known as hominins, appeared in Africa around 6-7 million years ago. Over millions of years, these early humans evolved, developing larger brains and more sophisticated tools.

Modern humans, Homo sapiens, emerged around 300,000 years ago. Our ability to adapt and innovate has allowed us to thrive and shape the world we live in today.

Conclusion

Understanding the origin and evolution of Earth is crucial for anyone preparing for the UPSC exam. It provides a foundation for comprehending more complex geographical and environmental concepts. By breaking down these topics into simple, relatable terms, we hope to make your study journey a bit easier and more enjoyable.

Remember, the Earth has a dynamic and fascinating history, much like our own lives. Embrace the learning process, stay curious, and keep exploring the wonders of our planet. Good luck with your UPSC preparations!

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FAQs on Earth Origin and Evolution for UPSC

1. What is the Big Bang Theory?

The Big Bang Theory is the most widely accepted explanation for the origin of the universe. It suggests that the universe began as an extremely hot and dense point around 13.8 billion years ago, which suddenly expanded, leading to the formation of galaxies, stars, and planets.

2. How did the solar system form?

The solar system formed about 4.6 billion years ago from a giant cloud of gas and dust called the solar nebula. The nebula collapsed under its own gravity, spinning into a flat disk with the Sun at its center. The remaining material clumped together to form the planets, moons, and other celestial bodies.

3. What led to the formation of Earth’s atmosphere and oceans?

Volcanic eruptions released gases from Earth’s interior, forming the early atmosphere, which consisted mainly of water vapor, carbon dioxide, methane, and ammonia. As Earth cooled, water vapor condensed to form rain, which filled basins and created the first oceans.

4. How did life on Earth begin?

Life on Earth began in the oceans about 3.5 billion years ago with simple, single-celled organisms. Over time, these organisms evolved into more complex forms, leading to the diversity of life we see today.

5. What is continental drift?

Continental drift is the theory that Earth’s continents were once part of a single supercontinent called Pangaea. Over millions of years, Pangaea broke apart, and the continents drifted to their current positions. This movement is driven by plate tectonics.

6. What are plate tectonics?

Plate tectonics is the theory that Earth’s outer shell (lithosphere) is divided into several plates that float on the semi-fluid mantle below. These plates constantly move, causing earthquakes, volcanic activity, and the formation of mountains.

7. When did humans first appear on Earth?

The first human-like beings, known as hominins, appeared in Africa around 6-7 million years ago. Modern humans, Homo sapiens, emerged around 300,000 years ago.

8. Why is understanding Earth’s origin and evolution important for UPSC preparation?

Understanding Earth’s origin and evolution provides a foundational knowledge necessary for comprehending more complex geographical and environmental concepts. This knowledge is crucial for answering questions in the geography section of the UPSC exam.

9. How did Earth’s continents move to their current positions?

Earth’s continents moved to their current positions through the process of continental drift, driven by plate tectonics. The movement of tectonic plates causes continents to shift, leading to their current configurations.

10. What is the significance of the solar nebula in the formation of the solar system?

The solar nebula is significant because it was the cloud of gas and dust that collapsed to form the Sun and the rest of the solar system. Its collapse and subsequent spinning led to the formation of planets, moons, and other celestial bodies.

Previous Years’ Questions on Earth Origin and Evolution for UPSC

UPSC Prelims Questions:

  1. Which one of the following is the correct sequence of events in the origin of Earth according to the Big Bang Theory?
    • A) Formation of the Universe, Formation of the Solar System, Formation of the Earth
    • B) Formation of the Solar System, Formation of the Universe, Formation of the Earth
    • C) Formation of the Earth, Formation of the Solar System, Formation of the Universe
    • D) Formation of the Universe, Formation of the Earth, Formation of the Solar System
  2. Consider the following statements:
    1. The Earth’s crust was initially molten.
    2. The formation of the oceans began only after the Earth cooled down.
    3. Life on Earth began in the oceans.
    Which of the statements given above are correct?
    • A) 1 and 2 only
    • B) 2 and 3 only
    • C) 1 and 3 only
    • D) 1, 2, and 3
  3. Which of the following gases was not part of the Earth’s early atmosphere?
    • A) Water vapor
    • B) Oxygen
    • C) Methane
    • D) Ammonia
  4. What is the term used to describe the theory that Earth’s continents were once joined together in a single landmass?
    • A) Plate Tectonics
    • B) Continental Drift
    • C) Sea-Floor Spreading
    • D) Volcanism

UPSC Mains Questions:

  1. Discuss the Big Bang Theory and its significance in understanding the origin of the universe. (200 words)
  2. Explain the process of the formation of the solar system. How did the Earth and other planets come into existence from the solar nebula? (250 words)
  3. Describe the early atmosphere of Earth. How did it evolve to its current state? (150 words)
  4. Critically analyze the theory of continental drift proposed by Alfred Wegener. How did it contribute to the development of the plate tectonics theory? (250 words)
  5. Evaluate the significance of ocean formation in the evolution of life on Earth. (200 words)

UPSC Geography Optional Questions:

  1. Trace the evolution of Earth’s lithosphere and discuss the role of plate tectonics in shaping Earth’s surface. (300 words)
  2. Describe the impact of volcanic activity on the formation of Earth’s early atmosphere. How did volcanic gases contribute to the development of oceans? (250 words)
  3. Examine the evidence supporting the theory of continental drift. How did this evidence lead to the acceptance of plate tectonics? (300 words)
  4. Discuss the significance of the fossil record in understanding the evolution of life on Earth. How do fossils provide insights into past climatic and environmental conditions? (250 words)

These questions cover a range of topics related to the origin and evolution of Earth, and they highlight the importance of these concepts in the UPSC examination. Studying these questions will help you gain a deeper understanding of the subject and prepare effectively for the exam.