Core
Also called: Nife · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 3 "Interior of the Earth"
Meaning
The core is the innermost part of the earth. It runs from about 2,900 km deep to the centre at about 6,371 km. It is made mostly of nickel and iron, so it is called nife. It has two parts. The outer core (2,900-5,150 km) is liquid, so S-waves cannot pass through it. The inner core (5,150-6,371 km) is solid. It is about 5,000-6,000 °C there, but huge pressure keeps the inner core solid. Liquid iron moving in the outer core produces the earth's magnetic field.
Example
S-waves from a large earthquake, such as the Sumatra-Andaman quake of 2004, are not recorded anywhere beyond 105° from the epicentre. This is because the liquid outer core stops them. This "S-wave shadow zone" is the main proof that the outer core is liquid.
Don't confuse with
- Mantle: it is mostly solid iron-magnesium silicate rock. The core is metal (nickel-iron), and its outer part is liquid.