Earth, Page 27: [Previous Page] [Next Page] [Class Home Page] Textbook pages 119 - 122

Plate Tectonics

The surface of the Earth is cracked like a hard-boiled egg. Individual land masses, referred to as `Plates', are in constant motion relative to each other.




The word tectonic refers to motion, and indeed, where plates are moving against each other, quite interesting things occur: Mid-Ocean Ridges. (Divergent) Spreading centers where the mantle is up-welling. (Middle of Atlantic Ocean)
Subduction Zones or Trenches. Where oceanic crust is being lost. Occurs a little at a time, with sudden motions. (Nazca Plate into the S.A. plate)
Transform Faults. Where two plates are sliding against each other, though no crustal material is lost. (San Andreas Fault)