Bridgmanite Mineral in Meteorite

Composition of Earth

• The Earth is made out of many things. 
• Deep inside Earth, near its center, lies Earth’s core which is mostly made up of nickel and iron. 
• Above the core is Earth’s mantle, which is made up of rock containing silicon, iron, magnesium, aluminium, oxygen and other minerals. 
• The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon, aluminium, iron, calcium, sodium, potassium and magnesium. 
• Earth’s surface is mainly covered with liquid water and its atmosphere is mainly nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapour and other gases.

Image Courtesy: Science 

• Crust:
  • The Earth’s outermost layer, its crust, is rocky and rigid. 
  • There are two kinds of crust: 
    • continental crust, and
    • Ocean crust. 
  • Continental crust is thicker, and predominantly felsic in composition, meaning that it contains minerals that are richer in silica. The composition is important because it makes continental crust less dense than oceanic crust.
  • Ocean crust is thinner and predominantly mafic in composition.  Mafic rocks contain minerals with less silica, but more iron and magnesium. Mafic rocks (and therefore ocean crust) are denser than the felsic rocks of continental crust.
  • The crust floats on the mantle.  Continental crust floats higher in the mantle than oceanic crust because of the lower density of continental crust.  An important consequence of the difference in density is that if tectonic plates happen to bring ocean crust and continental crust into collision, the plate with an oceanic crust will be forced down into the mantle beneath the plate with continental crust.
• Mantle:
  • The mantle is almost entirely solid rock, but it is in constant motion, flowing very slowly. 
  • It is ultramafic in composition, meaning it has, even more, iron and magnesium than mafic rocks, and even less silica.  
  • Although the mantle has a similar chemical composition throughout, it has layers with different mineral compositions and different physical properties.  
  • It can have different mineral compositions and still be the same in chemical composition because the increasing pressure deeper in the mantle causes mineral structures to be reconfigured.
  • Rocks higher in the mantle are typically composed of peridotite, a rock dominated by the minerals olivine and pyroxene. 
• Core:
  • The core is primarily composed of iron, with lesser amounts of nickel. 
  • Lighter elements such as sulfur, oxygen, or silicon may also be present. 
  • The core is extremely hot (~3500° to more than 6000°C). But despite the fact that the boundary between the inner and outer core is approximately as hot as the surface of the sun, only the outer core is liquid. 
  • The inner core is solid because the pressure at that depth is so high that it keeps the core from melting.