Class 7 – Social Science- NCERT – Geography
Chapter 2 Inside Our Earth
1. Interior of the Earth
– Crust – The outermost layer of the Earth, which is the thinnest and made of rocks and minerals.
– Mantle – The layer beneath the crust, extending up to 2900 km below the surface.
– Core – The innermost layer of the Earth, made of nickel (Ni) and iron (Fe), also called Nife. It has high temperature and pressure.
– Lithosphere – The solid outer part of the Earth, including the crust and upper mantle.
2. Rocks and Their Types
– Rock – Any natural solid mass of minerals that makes up the Earth’s crust.
– Igneous Rocks – Rocks formed from the cooling and solidification of molten magma.
– Extrusive Igneous Rocks – Formed when lava cools quickly on the Earth’s surface, creating fine-grained rocks (e.g., Basalt).
– Intrusive Igneous Rocks – Formed when magma cools slowly deep inside the Earth, creating large-grained rocks (e.g., Granite).
– Sedimentary Rocks – Rocks formed from sediments (small particles of rocks, sand, and minerals) that are compressed and hardened into layers (e.g., Sandstone).
– Metamorphic Rocks – Rocks that are formed when igneous or sedimentary rocks undergo heat and pressure, changing into a new type of rock (e.g., Limestone → Marble, Clay → Slate).
– Rock Cycle – The continuous process in which rocks change from one type to another over time.
3. Fossils and Minerals
– Fossils – The remains of dead plants and animals trapped in layers of sedimentary rocks.
– Minerals – Naturally occurring substances with a definite chemical composition and physical properties.
– Sial – The part of the continental crust made of silica (Si) and alumina (Al).
– Sima – The part of the oceanic crust made of silica (Si) and magnesium (Ma).
– Nife – The core of the Earth, made of nickel (Ni) and iron (Fe).
4. Word Origins (Etymology)
– Igneous – From the Latin word “Ignis”, meaning fire.
– Sedimentary – From the Latin word “Sedimentum”, meaning settle down.
– Metamorphic – From the Greek word “Metamorphose”, meaning change of form.
~~The END~~
Chapter 2 Inside Our Earth
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