Earthquakes and seismic waves - Physics


Earthquakes and Seismic Waves

The Earth and earthquakes

The Earth is not a solid ball, it has many layers.

  • The inner core is very hot and dense solid iron.
  • The outer core is very dense and liquid, mostly iron.
  • The mantle is hot, less dense and a mixture of solid and molten rock.
  • The crust is a very thin layer of solid rock.

The layered Earth (

The crust floats on a very hot liquid called magma. When magma comes to the surface from erupting volcanoes, it is called lava.

The Earth's crust is split into sections known as tetonic plates, which move very slowly due to convection currents in the magma. 

Sudden movement of tetonic plates causs the shaking of the ground, we call earthquakes.

  • As two plates try to slide past each other, friction between them at first prevents them from moving.
  • Eventually, the frictional forces cannot keep the plates still and they suddenly slip.
  • The immense energy stored in the compressed plates is released in the form of seismic waves.

Alfred Wegener first suggested the movement


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