General Knowledge - Basics of Planet Earth


  • Total surface area of the Earth is 510,100,500 sq. km, out of which −

    • The total land area is 148,950,800 sq. km (29.08% of total area) and

    • The total water area is 361,149,700 sq. km (70.92%).

  • Diameter of the Earth at Equator is 12,755 km, at the poles 12,712 km, and mean diameter is 12,734 km.

Diameter of Earth
  • Circumference of the Earth at Equator is 40,075 km and at the poles 40,024 km.

  • Equatorial radius of the Earth is 6,377 km.

  • The total mass of the Earth is 5.98 x 1024 kg.

  • Approximate age of the Earth is 4,500 million years.

  • The mean velocity of the Earth in its orbit (around the Sun) is 107,218 km/h.

  • The most abundant elements of the Earth are

    • Iron (about 32.5%),

    • Oxygen (29.8%),

    • Silicon (15.6%), and

    • Magnesium (13.9%)

Structure of Earth

  • The Earth is structured in three layers namely −

    • Crust,

    • Mantle, and

    • Core – Further classified as outer core (fluid layer) and inner core (solid layer).

Structure of Earth
  • The Crust is the uppermost layer of the Earth, largely composed of rocks. Its thickness ranges from 5 km to 60 km and density ranges from 2.7 to 3.

  • The Crust shares about 1 percent of Earth’s volume.

  • The Crust is categorized as ‘Continental Crust’ and ‘Oceanic Crust.’

  • The thickness of Continental Crust ranges from 30 km to 50 km. It is largely composed by granites, which density (i.e. 2.7) is lesser than the Oceanic Crust.

  • The thickness of Oceanic Crust ranges from 5 km to 10 km and it is composed primarily of basalt, diabase, and gabbro.

  • The density of Oceanic Crust is 3.0.

  • The most abundant element of Crust is Oxygen (46.6%) followed by Silicon (27.7%) and Aluminum (8.1%).

  • The Crust is also known as ‘Sial’ (i.e. Silicon and Aluminum)

  • The boundary between the Crust and the Mantle is known as the “Mohorovičić Discontinuity.”

  • The Mantle is located between the Crust and the (Outer) Core, which thickness is about 2885 km.

  • The Mantle shares about 83% of the Earth’s volume and about 65% of the mass.

  • The density of Mantle is about 3.4 g/cm3.

  • The upper layer of Mantle is known as ‘Asthenosphere.’

  • The Crust and the upper part of Mantle collectively known as ‘Lithosphere.’

  • The Core is mostly composed of iron and nickel; therefore, it is also known as ‘Nife’ (i.e. Nickel and Ferrous).

  • The Core shares about 16% of Earth’s total volume and 30% of the mass.

  • The thickness of the Core is about 3,400 km from the Mantle (likewise, the total depth from the Surface of the Earth is 6,300 km).

  • Core is categorized as outer core (which is in molten state) and inner core (which is in solid state).

  • Density of the inner core is about 13 g/cm3.