The Earth's Layers

Discussion Questions
Answers

1. How did Andrija Mohorovicic discover that the Earth's crust is made of less dense rock than the mantle.
   By studying earthquake waves. The waves moved at different speeds through the different layers The speed of movement through the crust was much slower than through the mantle. This meant that the crust was less dense and had to be made of a different material than the mantle.
   
    
2. Write in your own words the definition of a discontinuity.
   A discontinuity is the boundary between the layers of the Earth.
    
3. Name the four layers of the Earth in order from the outside to the centre of the Earth.
   1.Crust 2. Mantle 3. Outer Core 4. Inner Core
    
4. What causes the mantle to "flow"?
   The mantle flows because of convection currents that are caused by very hot material in the mantle rising, cooling, and then sinking. This circular pattern causes the mantle to flow.
    
5. What are the two main metals that make up the outer and inner core?
   Nickel and Iron
    
6. Describe in your own words how the Earth's layers were formed.
   As the Earth cooled the densest, heaviest materials sank to the middle of the Earth. The lightest materials rose to the top. This material was made mostly of rock. Rock makes up the crust of the Earth. Denser rock makes up the mantle. The most dense materials, iron and nickel, make up the inner and outer core.