PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth

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This PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth will help you in revision during exams.

PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth

→ Lithosphere: It includes the earth’s crust called Sial. The normal width of this part is almost 100 kms. It has more Silicon and Aluminium.

→ Minerals: These are those natural substances that are made up of one element or a combination of elements.

PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth

→ Rocks: The combined form of natural minerals is called Rocks. These are of three types Igneous, Sedimentary and Metamorphic.

→ Magma: In the depth of the earth, most substances are found in a melt state called Magma.

→ Lava: When magma reaches the earth’s surface, it is called lava.

→ Igneous and Metamorphic Rocks:

  • The molten lava cools down, gets solidified, and thus comes into existence-Igneous Rocks.
  • Metamorphic rocks come into existence through Igneous and Sedimentary rocks.
  • In fact, Igneous and sedimentary rocks undergo a transformation that is chemical as well as structural because of pressure and heat.
  • As a result, the construction and structure of these rocks changes, and these are called Metamorphic rocks.
  • Example: Granite is an igneous rock while Gneiss made up of Granite is a metamorphosized rock.

→ Metallic and Non-metallic Minerals: Metallic minerals contain metals like iron, silver, etc. while Non-metallic minerals don’t contain metals like Abhrak, Potassium, Gypsum, etc.

→ Preservation of Minerals: It takes hundreds of years the make minerals, so these must be preserved.

→ Crust: The outermost layer of earth.

→ Core: The innermost layer of the earth.

→ Sedimentary rocks: Any rock formed by the deposition of sediments.

PSEB 7th Class Social Science Notes Chapter 2 The Internal and External Face of the Earth

→ Mantle: The mantle is the intermediate layer between the crust and the core of the earth.

→ Minerals: A mineral is a naturally occurring substance having a definite chemical composition and physical properties.

→ Lithospheric plates: A large segment of earth crust that can ‘float’ across the heavier, semi-molten rock below.

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