General Knowledge – Rocks – Notes For W.B.C.S. Examination.

সাধারণ জ্ঞান – শিলা – WBCS পরীক্ষার  জন্য নোট ।

Rock is the solid mineral material that forms part of the surface of the earth, exposed on the Earth’s surface or underlying the soil.Continue Reading General Knowledge – Rocks – Notes For W.B.C.S. Examination.

Rock is divided into following three types −

Igneous Rocks

Sedimentary Rock

Metamorphic Rock

Igneous Rock

• Igneous Rock is normally formed by the solidification of the molten magma.
• All other types of rocks are formed by the igneous rock; therefore, igneous rock is also known as primary rock.
• About 95% of the Earth’s crust is made of igneous rock.
• Granite, Basalt, and Volcanic rock are the major types of igneous rock.

Sedimentary Rock

• The rocks, which is formed because of the deposition of weathered remains of igneous rocks, is known as ‘Sedimentary Rock.’
• Sedimentary rocks share 5% of the Earth’s surface, but cover (in terms of area) about 75% of Earth’s (exposed) surface.
• Sedimentary rocks also contain organic materials (i.e. source of energy for the human beings).
• Major examples of sedimentary rocks are Gypsum, Limestone, Chalk, Coal, Conglomerates, Sandstone, Claystone, etc.

Metamorphic Rock

• Because of the intense pressure, high fluctuating temperature, and presence and absence of moisture and chemicals, over a period of time, igneous rock or sedimentary rocks get modified (metamorphosed) and called as ‘Metamorphic Rock.’
• Major examples of metamorphic rock are Slate, Gneiss, Marble, Quartzite, etc.

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