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## Types of Rocks Rocks can be classified into three types based on their origin: igneous, sedimentary, and metamorphic rocks. ### Case Study The Peninsular Plateau is a flat-topped landmass made up of ancient crystalline, igneous, and metamorphic rocks. It was formed when the Gondwana land broke...

## Types of Rocks Rocks can be classified into three types based on their origin: igneous, sedimentary, and metamorphic rocks. ### Case Study The Peninsular Plateau is a flat-topped landmass made up of ancient crystalline, igneous, and metamorphic rocks. It was formed when the Gondwana land broke apart and drifted making it one of the oldest land masses on Earth. The plateau features wide, shallow valleys and rounded hills. 1. What caused the formation of the Peninsular Plateau? 2. Why is it considered one of the oldest land masses on Earth? 3. What is the reason behind the crystalline nature of the rocks in the plateau? 4. In which region of India can the Peninsular Plateau be found? ### Igneous rocks The geological history of regions like the Peninsular Plateau involves the formation of various types of rocks, including igneous rocks. Igneous rocks get their name from the Latin word "ignis," meaning fire, as they are formed by the cooling of molten materials called magma after volcanic eruptions. They solidify to create primary rocks. They are called primary rocks because they were the initial ones to form in the rock cycle and they do not contain any organic remains. Based on their mode of existence, igneous rocks are classified as intrusive igneous rocks and extrusive igneous rocks. - **Intrusive igneous rocks** Intrusive igneous rocks form when magma cools slowly below the earth's surface, resulting in large mineral crystals, such as granite and dolerite. - **Extrusive igneous rocks** Extrusive igneous rocks, on the other hand, form from the quick cooling of molten lava on the earth's surface and may have small crystals. Examples of extrusive igneous rocks include basalt and gabbro.