Earth's Structure
ICSE · Class 9 · Geography
Summary of Earth's Structure for ICSE Class 9 Geography. Key concepts, important points, and chapter overview.
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Earth’s interior is understood through indirect evidence such as earthquake waves, lava, temperature change, pressure, and density. The Earth is divided into three main parts: crust, mantle, and core. The crust is the outer shell, the mantle lies beneath it, and the core forms the central part. As d
Key Concepts
The crust is the outermost layer
The crust is the outermost layer of the Earth. The word Lithosphere comes from the Greek word Lithos, meaning rock. It is about 6 to 48 km thick and m
Sial is the upper
Sial is the upper, continental layer of the crust. It is made mainly of silica and aluminium, has a density of about 2.7, and is similar to granite. I
Sima is the lower
Sima is the lower, continuous layer of the crust. It is made mainly of silica and magnesium, has a density of about 2.95, and is similar to basalt. It
The Moho is the contact zone
The Moho is the contact zone between the crust and the mantle. It is named after the Yugoslav scientist who discovered it.
The mantle is the second layer
The mantle is the second layer of the Earth, lying between the crust and the core. It extends from about 35 km to 2900 km depth and is divided into th
Learning Objectives
- Understand the three main parts of the Earth: crust, mantle, and core
- Describe the composition and thickness of the crust, mantle, and core
- Explain the meaning of Sial, Sima, Moho, and Gutenberg Discontinuity
- Recognize how temperature, pressure, and density change with depth
- Understand the state and composition of the inner and outer parts of the Earth
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