The Earth and Its Layers

What does our Earth look like and how does it work?

The Earth's Chemical Layers

As the Standard SC.912.E.6.1 states, we'll be learning about the Earth's layers today.

Earth is composed of 3 main layers and then some sub layers.

The Main layers are;


  • Crust - about 5-70 km in thickness (oceanic crust is thinner than continental crust)
  • Mantle - about 2,885 km in thickness (composed of upper and lower mantle)
  • Core - 3,486 km in thickness (composed of an Inner and outer core)

The Earth's Mechanical Layers

Each of Earth's layers is composed of sublayers, each with unique chemical and mechanical properties.



  1. The Lithosphere, the outermost part of the Earth that consists of the crust and some of the upper mantle. It is about 100 km thick and thicker in continents than it is on oceans.
  2. The Asthenosphere is the layer beneath, measuring around 100 km thick. It is mostly mantle and has little strength. This is because the Asthenosphere is more flexible and can accommodate to the shifting plate tectonics.
  3. The Mesosphere lies beneath, and much like the Asthenosphere, it is softer and flows, however it flows much more than the Asthenosphere, this is key to the movement of plate tectonics.
  4. The Outer Core is the part of the Core that is liquid, mostly molten nickel and Iron. This is the only internal part of the Earth that is Liquid.
  5. The Inner Core is the final part of the Earth's layers, compressed with 3 million times more pressure than the atmosphere's pressure on Earth, the Earth's Inner Core is so hot and compressed that it is a solid and has a magnetic orientation and magnetic force that protects our Earth's atmosphere from the Sun's solar winds.
Why Does The Earth Have Layers?

The Earth's Crust and Plate Tectonics

SC.912.E.6.3

Earth has on it's crust, right on top of the Mantle enormously large pieces of land that we call Plates. These plates often have a continent or some piece of land in it, and as they move, so do the land masses above them.


Plates flex and move around, colliding and separating from each other. They behave this way because of the movement of the semi-molten mantle rising, cooling, sinking, melting and then heating up and rising again.


There are 3 main types of plate tectonic movement;


  1. Convergent - Happens when two plates collide against each other, the less dense sinking below the bigger, more dense plate.
  2. Divergent - Occurs when 2 plates separate from each other, leaving empty space between where more magma can rise and cool, forming more crust.
  3. Lateral - to plates sliding past each other, grinding, moving and changing, without clashing or separating.


Plates move very slowly, often on an average of an inch per year. This is why these changes are hard to notice, and require time.

Plate Tectonics Explained