Earth’s Interior: Layers, Composition, and Characteristics

Posted on Sep 29, 2024 in Geology

Chapter 4: Earth’s Structure

Layers of the Earth’s Interior

1. NIFE: The Earth’s Core

Q: In which part of the earth is NIFE found? What is it composed of?

A: The core of the earth is called NIFE. It is composed of Nickel (Ni) and Iron (Fe).

2. Pressure and Temperature in the Earth’s Interior

Q: What are the consequences of the pressure and temperature in the interior of the earth?

A:

  • The temperature in the core ranges from 4400°C to about 6000°C.
  • Pressure and density increase towards the interior of the earth.
  • The inner core is in a solid state due to high pressure and density, which compresses the molten rock material.
  • The outer core is in a liquid state as there is not enough pressure to keep it in a solid state.

3. Meteorites and Earth’s Interior

Q: How do meteorites help scientists to know about the interior of the earth?

A: The earth is said to be constituted of the same materials as meteorites. So, scientists study meteorites to know more about the interior of the earth.

4. Composition of the Earth’s Crust

Q: What is the composition of the earth’s crust?

A:

  • The crust of the earth is a sphere of solid rocks.
  • It is only 1% of the earth’s mass.
  • It is made up of rocks with a large content of silicates, feldspar, mica, etc.
  • The crust is divided into two broad divisions: SIAL and SIMA.
  • SIAL is composed of Silica and Aluminium, while SIMA is composed of Silica and Magnesium.

5. The Lithosphere

Q: What is the lithosphere?

A: The crust of the earth is called the lithosphere as it is a sphere of solid rocks with a thickness of 60 km below high mountains and just 5-10 km below the oceans.

6. Layers and Boundaries of Earth’s Interior

Q: Name the three layers of the earth’s interior. Name their boundaries.

A:

  • The three layers of the earth’s interior are the Core, Mantle, and Crust.
  • The boundaries between the three layers of the earth’s interior are:
    • Gutenberg Discontinuity: It lies between the mantle and the core.
    • Mohorovicic Discontinuity: It lies between the crust and the mantle.

7. The Mantle

Q: Describe the mantle. State its two chief characteristics.

A:

  • The mantle lies below the crust.
  • It makes up 84% of the earth’s total volume.
  • The mantle is divided into two parts: the upper mantle and the lower mantle.
  • Two chief characteristics of the mantle are:
    • Its average thickness is 2900 km.
    • The temperature varies between about 1000°C to around 3700°C.

8. The Asthenosphere

Q: Where is the asthenosphere found? In which form does it exist?

A: The asthenosphere is found at a depth of around 100-410 km. It exists in a partially molten form.

9. Moho vs. Gutenberg Discontinuity

Q: Write one difference between Moho Discontinuity and Gutenberg Discontinuity.

A:

  • Moho Discontinuity: The boundary between the crust and the mantle.
  • Gutenberg Discontinuity: The boundary between the mantle and the core.

10. Solid State of Earth’s Interior

Q: Why is the earth’s interior in most part found in a solid state despite great heat and pressure?

A: The solid state of the inner core is due to high density and pressure, which have compressed the molten rock material.

Detailed Description of Earth’s Layers

L1. Layers and Chemical Composition

Q: Describe the layers of the interior of the earth and their chemical composition.

A: The layers of the interior of the earth are as follows:

  • Crust: It is the topmost layer of the earth. It is made up of rock with a large content of silicates, feldspar, mica, etc. It also contains silica and aluminium.
  • Mantle: It lies between the crust and the core. It can be divided into the upper and lower mantle. The upper mantle is solid, while the lower mantle is partially molten. It is mainly composed of oxygen, silicon, and magnesium.
  • Core: The core is the innermost inaccessible part of the earth. It is mainly composed of Nickel and Iron.

2. Transitional Zones

Q: There are two transitional zones between the two consecutive layers of the interior of the earth. Name them and state their chief characteristics.

A:

  • Moho Discontinuity: The transitional zone between the crust and the mantle. It is the dividing zone between the solid and semi-solid states of rocks due to the increase in temperature with an increase in depth. It is found at about 8 km beneath the oceans and about 32 km beneath the continents.
  • Gutenberg Discontinuity: The boundary between the mantle and the core. It begins at a depth of 2800 km. Below this zone, both density and temperature increase.

3. Geographical Reasons

Q: Give a geographical reason for each of the following:

A:

  1. Temperature starts rising gradually towards the interior of the earth.
    Due to increasing density and pressure, the temperature increases gradually towards the interior of the earth.
  2. The asthenosphere is in a semi-molten state.
    The asthenosphere is in a semi-molten state because of high temperature, pressure, and density.
  3. The inner core of the earth is in a solid state.
    The inner core of the earth is in a solid state due to high density and pressure.

4. Labeling and States of Earth’s Parts

Q (i): Label the parts: (1), (2), (3), (4), and (5).

A: (1) Atmosphere, (2) Crust, (3) Mantle, (4) Core, (5) Ocean

Q (ii): Name the state (solid, liquid, or gas) in which each part exists.

A: (1) Atmosphere – Gaseous, (2) Crust – Solid, (3) Mantle – Semi-molten and solid, (4) Core – Solid, (5) Ocean – Liquid

Q (iii): Which part of the earth is suitable for human habitation? Why?

A: The crust is suitable for human habitation due to favorable conditions for survival, i.e., the atmosphere for air, the lithosphere for settlement due to ideal temperature, the hydrosphere for the hydrological cycle for providing rainfall and fresh water bodies on the earth, and oceans for navigation and trade routes, etc.

5. Characteristics of Earth’s Crust

Q: State two chief characteristics of the earth’s crust.

A:

  • It is a sphere of solid rocks with a thickness of 60 km below high mountains and just 5-10 km below the oceans.
  • It is made up of rocks with a large content of silicates, feldspar, mica, etc.

6. Earth’s Magnetic Field

Q: Which layer is responsible for the earth’s magnetic field? Why?

A: The core of the earth is responsible for the earth’s magnetic field as it is composed of iron and nickel.

7. Geographical Reasons

Q: Give a geographical reason for each of the following:

A:

  1. NIFE is so-called.
    NIFE is so-called as Ni stands for Nickel and Fe stands for Iron.
  2. The core of the earth is the most inaccessible part of the earth.
    The core of the earth is the most inaccessible part of the earth because it lies thousands of kilometers deep inside the earth.
  3. The earth’s crust undergoes many changes.
    The earth’s crust undergoes many changes due to the forces of nature.