Core Within Earth’s Core


    In News

    • The recent findings show that the Earth’s innermost inner core completely differs from the remainder of the planet’s centre.

    More about the study

    • About:
      • In order to comprehend planetary origin and evolution, scientists have been investigating the Earth’s centre for a very long time.
      • Until recently, it was believed that the crust, mantle, outer core, and inner core made up the structure of the Earth. 
    • Fifth layer:
      • New research published in Nature Communications confirms that there is actually a fifth layer.
      • Researchers said the intensive study of Earth’s deep interior, based on the behavior of seismic waves from large earthquakes, confirmed the existence of a distinct structure inside our planet’s inner core – a wickedly hot innermost solid ball of iron and nickel about 800 miles (1,350 km) wide.
    • Earth’s internal structure:
      • Earth’s diameter is about 7,900 miles (12,750 km). The planet’s internal structure comprises four layers: 
        • A rocky crust on the outside, 
        • A rocky mantle, 
        • An outer core made of magma and 
        • A solid inner core
          • This metallic inner core, about 1,500 miles (2,440) wide, was discovered in the 1930s, also based on seismic waves traveling through Earth.
    • Significance of Earth’s inner core (IC):
      • Earth’s inner core (IC), which accounts for less than 1% of the Earth’s volume, is a time capsule of our planet’s history
      • As the IC grows, the latent heat and light elements released by the solidification process drive the convection of the liquid outer core, which, in turn, maintains the geodynamo.

    More about the layers of Earth’s interior

    • The Crust 
      • It is the outermost solid part of the earth. 
      • It is brittle in nature. 
      • The thickness of the crust varies under the oceanic and continental areas. 
        • The oceanic crust is thinner compared to the continental crust. 
        • The continental crust is thicker in the areas of major mountain systems.
    • The Mantle 
      • It is the portion of the interior beyond the crust. 
      • The asthenosphere
        • The upper portion of the mantle is called the asthenosphere. 
        • The word ‘astheno’ means weak.
        • It is the main source of magma that finds its way to the surface during volcanic eruptions.
      • The lower mantle extends beyond the asthenosphere. 
      • The lithosphere 
        • The crust and the uppermost part of the mantle are called lithosphere. 
        • It is in a solid state.
    • The core 
      • The earthquake wave velocities helped in understanding the existence of the core of the earth. 
      • The outer core is in a liquid state while the inner core is in a solid state. 
      • The core is made up of very heavy material mostly composed of nickel and iron. 


    Seismic waves

    • About:
      • When an earthquake occurs, the shockwaves of released energy that shake the Earth and temporarily turn soft deposits are called seismic waves.
        • The term comes from the Greek ‘seismos’ meaning ‘earthquake’.
    • Occurrence:
      • These are usually generated by movements of the Earth’s tectonic plates but may also be caused by explosions, volcanoes and landslides.
    • Seismographs:
      • Seismologists use seismographs to record the amount of time it takes seismic waves to travel through different layers of the Earth.
    • There are three basic types of seismic waves: 
      • P-waves, S-waves and Surface waves (Rayleigh and Love waves)
        • P-waves and S-waves are sometimes collectively called Body Waves.
      • Body waves:
        • Generated due to the release of energy at the focus and move in all directions travelling through the body of the earth. Hence, the name – body waves.
        • Travel only through the interior of the earth.
        • Faster than surface waves.
        • There are 2 types of body waves: P- primary waves and S-secondary waves.
          • P waves travel through gaseous, liquid and solid materials whereas S waves travel only through solid materials.
      • Surface Waves:
        • When the body waves interact with surface rocks, a new set of waves is generated called surface waves. 
        • These waves move along the earth’s surface.
        • Surface waves are transverse waves in which particle movement is perpendicular to the wave propagation. Hence, they create crests and troughs in the material through which they pass.
        • They are the most damaging waves. 
        • 2 common surface waves are Love waves and Rayleigh waves.
    • Speed of different Waves in descending order: 
      • Primary Waves > Secondary Waves > Love Waves > Rayleigh Waves.

    Source: TH