photo.jpg

### Quick-thinking Fill in the blanks. 1. **The core** is the innermost layer of the Earth. 2. **The upper part of the Earth's crust** that forms the large landmasses is known as the **continental crust**. 3. **The lower part of the Earth** is also known as **Barysphere**. ### Rocks and Minera...

### Quick-thinking Fill in the blanks. 1. **The core** is the innermost layer of the Earth. 2. **The upper part of the Earth's crust** that forms the large landmasses is known as the **continental crust**. 3. **The lower part of the Earth** is also known as **Barysphere**. ### Rocks and Minerals The Earth's crust is primarily made up of rocks, such as granite, slate and limestone, and minerals such as coal, iron ore and mica. Rocks are solid masses made up of minerals found in the Earth's crust. The term `rock` can refer to both `hard, dense materials` like granite and `softer, loose particles` like sand, silt, and clay. Rocks come in a variety of colors, textures, sizes, and structures because of different types and amount of `minerals` present in them. Minerals, on the other hand, are naturally occurring `inorganic substances` that are `solid and have a distinct chemical composition` such as in iron (Fe), gold (Au) and sodium (Na). ### Rocks 1. Rocks are solid masses of minerals obtained from the Earth's crust. 2. A rock has no definite chemical composition. 3. Examples of rocks include basalt, granite, sandstone and quartz ### Minerals 1. Minerals are solid inorganic substances that occur naturally. 2. Minerals have a definite chemical composition. 3. Examples of minerals include Iron, silicon, magnesium and sodium. **Did You Know** Rocks are mined to extract minerals. Such rocks are commonly called `ores`. After removing the minerals, the leftover rock is called `taillings`. ### 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 metamorphic rocks. It was formed when the Gondwana land broke apart and the plateau features rounded hills. Based on this information, answer the following questions: 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? 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 and may have large mineral crystals, such as granite and dolerite. ### Extrusive igneous rocks Extrusive igneous rocks, on the other hand, form from lava that cools quickly after flowing onto the Earth's surface and may have small crystals. Examples include basalt and gabbro. ### Word Galaxy * **crystal** a mineral that forms in a distinct shape and structure when it solidifies, unlike rocks which are aggregates of minerals.