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What is Macro-Geology??

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Big things happen to planet Earth, like earthquakes, volcanoes and tsunamis.  These are obvious to an observer (and often television viewers).  These events, along with landslides, caves, and other forms of erosion, can be called Macro-Geology.


Underlying many of the more spectacular events is the theory of Plate Tectonics.  Simply put, plate tectonics is the concept of new crustal material (Earth’s surface) being continually made and consumed.

The idea of plate tectonics debuted in 1962.  Before that time, scientists had struggled to explain how mountains were formed.  Plate tectonics explains mountains, ocean trenches, volcanoes and much more.  Plate tectonics is the concept that the earth’s surface (about the top 10-120 miles) is mobile and floats on the layer underneath.  That underlying layer is rock, but hotter and slightly more fluid, allowing the overlaying rocks to move.  (The reason that the surface layers move is still under study.) 


Rocks that make up Earth’s land masses are generally lighter than those that make up the ocean floors.  Therefore, when ocean-floor rock moves against land rock, the ocean-floor rock goes beneath the land rock in a process called subduction.  The subducted rock is melted and modified, and comes back to the surface as magma, lava emitted by volcanoes.


When the plates bump into, push against each other, the adjoining rocks are stressed.  This stress is responsible for several things: one being earthquakes when the stress is removed quickly; another effect of the stress is the folding of the land -- rocks -- into mountains.


Macro-Geology can be explained in two broad categories:  Building, or Depositional, and Tearing Down.  Building includes activities such as volcanoes, earthquakes and of course plate tectonics discussed above.  Tearing down is another way to look at erosion.  The erosion agents of water and wind create some of our favorite places, for instance the Grand Canyon and Mammoth Cave.

Build It Up, Tear It DownText Box: To learn more about the Building processes, click in this box.
Text Box: To learn more about the Tearing Down processes, click in this box.