Earth is composed of four main layers - crust, mantle, outer core, and inner core. The crust is the outermost layer and is made up of either continental or oceanic crust. Below the crust is the mantle, which is divided into lithosphere, asthenosphere, upper mantle, and lower mantle. The outer core is a liquid layer made of nickel and iron that generates Earth's magnetic field. The inner core is made of solid iron deep within Earth. Overall, Earth's composition is approximately 34.6% iron, 29.5% oxygen, and 15.2% silicon.

1. INTRODUCTION TO EARTH

3. SOME FACTS ABOUT THE EARTH

6. STRUCTURE OF EARTH The structure of earth (also referred as cross–section) is divided into mainly four layers namely Crust, Mantle, Inner Core and Outer Core .

7. STRUCTURE OF EARTH

8. STRUCTURE OF EARTH Divisions,Thickness & Materials of the layer

14. STRUCTURE OF EARTH

15. STRUCTURE OF EARTH

16. COMPOSITION OF EARTH As discussed earlier, the mass of the Earth is approximately 5.98×10 24 kg. When taken as a whole, the Earth's chemical composition (by mass) has been approximated as given in the table below. The students should remember the top three with their percentages S.No. Component Percentage by Mass 1 Iron 34.6% 2 Oxygen 29.5% 3 Silicon 15.2% 4 Magnesium 12.7% 5 Sulfur 2.4% 6 Nickel 1.9% 7 Calcium 1.5% 8 Aluminium 1.4% 9 Trace Elements 0.8%