Earth Systems


Summarize the structure of the earth, including the layers, the  mantle and core based on the relative position, composition and density.

  • The earth is composed – primarily – of rock. 
  • Three-fourths of the earth’s surface is covered by a relatively thin layer of water (some of it frozen), and the entire planet is surrounded by a relatively thin layer of gas we call the atmosphere. 
  • The Earth has a solid inner core that is surrounded by a liquid outer core. 
  • The inner core is a solid section of the Earth and is unattached to the mantle, being suspended by the molten outer core. 
  • The inner core is predominantly iron metal with significant amounts of the element nickel. 
  • This inner layer in mutual combination with the rotational motion of the Earth creates a dynamo effect where a force field is generated.  This field is also known as Earth’s magnetic field.
  • In terms of the physical aspects of the outer core, the layer is dense but not as dense as pure molten iron. 
  • Surrounding the entire dense, metallic core is a thick, hot, convective layer called the mantle.  
  • The crust consists of many continental and oceanic plates that have slowly moved and changed positions on the globe throughout geologic time.

Explain how crustal plates and ocean basins are formed, move and   interact using earthquakes, heat flow and volcanoes to reflect forces   within the earth

  • The earth's plates sit on a dense, hot, somewhat melted layer of the earth. 
  • These plates range in thickness from a few to more than 100 kilometers.  
  • Lithospheric plates the size of continents and oceans constantly move at rates of centimeters per year as a result of movements in the mantle coupled with characteristics of the plates themselves. 
  • The plates move very slowly, pressing against one another in some places and pulling apart in other places, sometimes scraping alongside each other as they do. 
  • Mountains form as two continental plates, or an ocean plate and a continental plate, press together.
  • Major geological events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions.  There are worldwide patterns to major geological events (such as earthquakes, volcanic eruptions, and mountain building) that coincide with plate boundaries. 
  • Ocean floors are the tops of thin oceanic plates that spread outward from mid-ocean rift zones.
  • Land surfaces are the tops of thicker, less-dense continental plates. 
  • Earth is made up of 4 different layers: inner core, outer core, mantle, crust. 
  • Seismologists have studied how wave energy travels through the different layers of Earth. 
  • Waves have characteristics: frequency, wavelength, amplitude and speed. 
  • During an earthquake, energy is released into the Earth as: Primary waves, Secondary waves and Surface waves.