Structure of the Earth

STRUCTURE OF THE EARTH

The Lithosphere

•  includes the brittle upper portion of the mantle and the crust, 
• the most rigid of the Earth's layers
  
• although the rocks of the lithosphere are still considered elastic, they are not viscous
• the coolest of Earth’s layers
• Oceanic lithosphere is associated with oceanic crust, and is slightly denser than continental lithosphere
• Continental lithosphere, associated with continental crust, can be much, much thicker than its oceanic cousin

The Asthenosphere 

•  zone of Earth’s mantle lying beneath the lithosphere
• believed to be much hotter and more fluid than the lithosphere
• heated by contact with hot materials that make up the mesosphere beneath it
• extends from about 100 km (60 miles) to about 700 km (450 miles) below Earth’s surface
• convection currents generated within the asthenosphere push magma upward through volcanic vents
• Convection currents also stress the lithosphere above, and the cracking that often results manifests as earthquakes
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