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Earth's Structure — Revision Notes

ICSE · Class 9 · Geography

Earth's Structure revision notes for ICSE Class 9 Geography: 4 topics in quick points. Part of the ICSE Class 9 Geography syllabus.

51 questions34 flashcards4 formulas & key relations5 concepts

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A cross-section diagram showing the Earth's main layers: Crust, Mantle (Upper and Lower), and Core (Outer and Inner), with their approximate depths and key compositions.
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Key Topics to Revise

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1. Earth’s Interior: Main Layers

  • Earth is composed of three parts: crust, mantle, and core.
  • The crust is the outermost layer and is also called the lithosphere.
  • The mantle lies between the crust and the core.
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2. Crust: Lithosphere, Sial, and Sima

  • The word lithosphere comes from the Greek word Lithos meaning rock.
  • The crust is about 6 to 48 km thick in one description and 5 to 60 km in another description.
  • The crust has two layers: Sial and Sima.
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3. Temperature, Pressure, and Density Inside Earth

  • Temperature increases as depth increases.
  • The rate of temperature increase is 1°C for every 32 metres of descent.
  • At a depth of 48 km, the temperature is between 1200°C and 2000°C.
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4. Mantle: Position, Extent, and Parts

  • The mantle is the second layer of the Earth.
  • It lies between the crust and the core.
  • Its upper boundary is the Mohorovicic Discontinuity and its lower boundary is the Gutenberg Discontinuity.

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Full Notes

Key Concepts

The crust is the outermost layerSial is the upperSima is the lowerThe Moho is the contact zoneThe mantle is the second layer

Frequently Asked Questions

What are the important topics in Earth's Structure for ICSE Class 9 Geography?
Key topics in Earth's Structure include Earth’s Interior: Main Layers, Crust: Lithosphere, Sial, and Sima, Temperature, Pressure, and Density Inside Earth, Mantle: Position, Extent, and Parts. Study these first, then practise questions on each for Class 9 exams.
How should I revise Earth's Structure for Class 9 exams?
Learn the core ideas first, then work through the 51 practice questions on Earth's Structure. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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