Earth

1
Earths Structure and Movement

• Earths Composition and Plate Tectonics

2
Density Stratification
3
Evidence of Composition

• Earthquakes
• Seismic Waves Travel through earth, bend and
  reflect while travelling back to the surface.
  This can tell us about the Earths composition.
  (2 types)
• 1) Surface Waves move on surface, property
  damage
• 2) Body Waves Primary (P) Waves and
  Secondary (S) Waves
• Seismograph Measures P waves which travel faster
  then S waves

4
Important Events

• 1900 Richard Oldham Waves travelled at
  different speeds as they moves through the earth
  due to density differences.
• 1906 Oldham - S waves are absorbed when they hit
  the earths core. (Shadow Zone portion of earth
  where S waves do not exist.)
• 1935 Lehmann P waves speed up at the core due
  to increased density

5
Confirmation of Layers

• 1964 Near Anchorage, Alaska earthquake with
  magnitude of 9.2.
• Seismographs all over the world monitored the P
  and S waves, data confirmed the existing
  knowledge of the earths density stratification.

6
Also called Mantle
7
The Layers (Outer to Inner)

• Crust 0.4 of Earths Total Mass
• Less then 1 of its volume
• Oceanic Mostly Basalt (Heavy)
• Continental Mostly Granite (Lighter)
• Mantle 68 of Earths Total Mass
• 83 of its volume
• Mostly Silicon and Oxygen
• Core Mostly Iron and Nickel
• 31.5 of Earths Total Mass
• 15 of its volume

8
Outer Layers

• Crust and upper Mantle float (2 Parts) over the
  warmers inner MantleCrust and Upper Mantle
• 1) Lithosphere cool, outer ridge (Crust and
  outer most Mantle
• 2) Asthenosphere hot, partially melted upper
  Mantle
• Lower Mantle
• Hotter then upper but does not melt due to
  pressure

9
The Core

• Outer Core Dense Liquid
• Inner Core Solid

10
Keeping the Continents Afloat

• Buoyancy Thicker continental crust and
  lithosphere floats on the flowing layers below.