Describe the nature and mode of origin of the main types of rock at the earth's crust.

Rocks present in the Earth's crust are vital for extraction of minerals and oils. However, they differ in terms of their nature and mode of origin. [Diagram description: Rock Cycle showing formation of Igneous Rock through cooling, then to Sedimentary Rock through erosion and deposition, and to Metamorphic Rock through heat and pressure, with processes labeled] A. Igneous rocks: 1. They are formed due to volcanic eruption, when the lava cools down. 2. If the lava is cooled down quickly, it has smooth granules [eg: Granite, Basalt etc.]

it has smooth granules [eg: Granite, Basalt etc.] B. Sedimentary Rock: (1) It is formed due to deposition of sediments and lithification leading to layering. (2) It can be of different types such as organic coal or mechanical conglomerate etc. C. Metamorphic rock: (1) It is formed due to the subjection of other rocks to high pressure and temperature. (2) It can be of different origin such as marble, gneiss etc. Various rocks signifies the various geomorphological processes of earth.