Dr. Manishika Jain explains the NCERT Class 7 Geography Chapter 2: Inside our Earth\r<br>\r<br>Onion Peel: Demonstrating Earths Interior\r<br>Crust\r<br>Continental - Silica & Aluminum (SIAL) – 35 km\r<br>Oceanic – Silica & Magnesium (SIMA) – 5 km \r<br>B/w upper & lower crust – Conrad Discontinuity \r<br>B/w crust & mantle – Moho Discontinuity \r<br>Jigsaw puzzle\r<br>Thinnest Layer\r<br>\r<br>\r<br>Mantle\r<br>About 2900 km thick\r<br>85% by volume\r<br>64% by mass\r<br>Made of iron but mainly silicates\r<br>Asthenosphere – Upper mantle – Convection currents \r<br>Viscous, weak and ductile\r<br>Just below lithosphere\r<br>Main source of Magma\r<br>B/w Upper & lower mantle – Repetti Discontinuity\r<br>B/w Mantle & Core – Guttenberg Discontinuity\r<br>Core\r<br>Radius of about 3500 km\r<br>Made of Iron & Nickel (NIFE)\r<br>High temperature & pressure \r<br>15% of earths volume\r<br>32.5% of earths mass\r<br>B/w Outer & Inner Core – Lehmann Discontinuity \r<br>Outer Core – Liquid (Slow Moving – Produces Earths Magnetic Field)\r<br>Pressure, Density increases towards center\r<br>\r<br>Rocks\r<br>Earths Crust\r<br>Natural mass of matter that makes the crust\r<br>Differ in Size, Color & Texture\r<br>3 Types of Rocks\r<br>Igneous\r<br>Sedimentary\r<br>Metamorphic\r<br>Igneous Rocks\r<br>Molten Magma Cools & Solidifies\r<br>Also known as Primary Rocks\r<br>Two Types\r<br>Intrusive – Cools inside, Slowly cools, Forms Large grains - Granite\r<br>Extrusive – Comes on Surface – Basalt (Deccan Plateau) – Fine Grained\r<br>\r<br>Sedimentary Rocks\r<br>Rocks roll, crack & hit to break\r<br>Sediments are transported\r<br>Then compressed & hardened\r<br>Sandstone – made from sand\r<br>Red Fort – red sandstone\r<br>Include fossils\r<br>Metamorphic Rocks\r<br>Igneous & Metamorphic change under heat & pressure\r<br>Clay → Slate\r<br>Limestone → Marble\r<br>Taj Mahal – White Marble\r<br>Rock Cycle – Transformation\r<br>Minerals\r<br>Naturally occurring substances \r<br>Have certain physical properties \r<br>Definite chemical composition\r<br>Fuels – Coal, Petroleum & Natural Gas\r<br>Industries – Iron, Aluminum\r<br>Medicines – Calcium, Phosphorus, Magnesium\r<br>For NCERT Based questions refer - \r<br>\r<br>For IAS Refer -
