Dr. Manishika Jain explains the NCERT Class 7 Geography Chapter 2: Inside our Earth\rbr\rbrOnion Peel: Demonstrating Earths Interior\rbrCrust\rbrContinental - Silica & Aluminum (SIAL) – 35 km\rbrOceanic – Silica & Magnesium (SIMA) – 5 km \rbrBw upper & lower crust – Conrad Discontinuity \rbrBw crust & mantle – Moho Discontinuity \rbrJigsaw puzzle\rbrThinnest Layer\rbr\rbr\rbrMantle\rbrAbout 2900 km thick\rbr85 by volume\rbr64 by mass\rbrMade of iron but mainly silicates\rbrAsthenosphere – Upper mantle – Convection currents \rbrViscous, weak and ductile\rbrJust below lithosphere\rbrMain source of Magma\rbrBw Upper & lower mantle – Repetti Discontinuity\rbrBw Mantle & Core – Guttenberg Discontinuity\rbrCore\rbrRadius of about 3500 km\rbrMade of Iron & Nickel (NIFE)\rbrHigh temperature & pressure \rbr15 of earths volume\rbr32.