Hazards 2


At the centre of the Earth is the core, which is split into an inner core and an outer core:

  • The inner core is a solid ball containing lots of iron and nickel.
  • The outer core is semi-molten and also contains lots of iron and nickel.

Around the core is the mantle, which is mostly made of silicate rocks:

  • The part of the mantle nearest the core is quite rigid.
  • The layer above this, called the asthenosphere, is semi-molten.
  • And the very, very top bit of the mantle is rigid.

The outer layer of the Earth is called the crust.

The rigid top part of the mantle and the crust together are called the lithosphere.

There are two types of crust - continental and oceanic:

  • Continental crust is thicker (30-70 km thick) and less dense.
  • Oceanic crust is thinner (6-10 km thick) and more dense.

The core and mantle are very hot - the inner core is about 6,000 degrees and the mantle is around 1,000-3,500 degrees. This heat is the Earth's main source of internal energy. Some of the heat energy is left over from when the Earth formed, and some comes from radioactive decay of elements, such as uranium.

The Earth's surface is separated into tectonic plates:

The lithosphere is divided into…


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