PLATE TECTONICS & BOUNDARIES (M2)

• Plate Tectonics


  The theory is that Earth's outer shell is divided into large slabs of solid rock, called "plates", that glide over Earth's mantle, the rocky inner layer above Earth's core.
• Alfred Wegener 


  A German Meteorolgist. Hypothesized that all of the continents were at one time connected as one large mass called Pangaea.
• Plates


  The Earth's crust and upper mantle are broken into sections called plates. It move around on top of the mantle like rafts.
• Continental Drift Theory

  Observation that the continents fit together like puzzle pieces, and may once have been connected.
• Ideas that supported Wegener's Theory:

  • Matching Fossil plants and reptile remains found on two continents.
  • Nearly identical sedimentary rock types of same age in widely separate location.
• Plate Tectonics Theory:


  Earth's lithosphere is composed of fragments or plates that move around and interact with one another.
• Plate Tectonics is thought to be caused by convection currents in Earth's mantle. It can also be a direct cause of forming mountain ranges.
• Mountain Ranges


  Formed due to the movement of plates, either apart or toward each other. (Some are formed underwater or on seabed, or on top of continental crust.)
• Mid-Ocean Ridge


  An underwater mountain system that consists of various mountain ranges.
• Volcano distribution 


  Mostly found along plate margin or areas where there is subduction of plates.
• Pacific Ring of Fire


  Where many active volcanoes are found.
• Types of Plate Boundaries

  • Divergent Plate Boundary
  • Convergent Plate Boundary
  • Transform Plate Boundary

  
• Seafloor Spreading 


  A geologic process where there is gradual addition of new oceanic crust in the ocean floor through volcanic activity while moving the older rocks away from the mid-oceanic ridge. The mid-ocean ridge is where the seafloor spreading occurs, in which tectonic plates—large slabs of Earth's lithosphere—split apart from each other.
• Lithospheric Plates


  The moving of irregularly shaped slabs that fit together to form the surface of the Earth's crust.
• Subduction


  Process in which DENSER crust (oceanic crust) moves below, toward the asthenosphere, forming a volcano.
• Convergent plate boundary

  Plates move towards each other which results to a collision. (Occurs when two plates move together)
• Divergent Plate Boundary 


  Plates move apart from each other, resulting in the production of a new seafloor.
• Transform Plate Boundary 


  The plates slide past horizontally to each other without destroying the lithospheric plates.
• Three types of Collisions (Convergent plate boundaries):

  • Oceanic-Continental
  • Oceanic-Oceanic
  • Continental-Continental
• Oceanic-Continental convergence 


  Type of collision between an oceanic crust and continental crust. Where subduction happens.
• Convergent plate boundary causes one of the slabs of the lithosphere to subduct beneath an overriding plate. It is also known as the destructive plate boundary.
• In subduction zone, volcanoes occurs.
• Trench


  A deep, narrow depression on the ocean seafloor caused by the collision or subduction.
• Rift Valley


  Another feature that results from plate movement.
• Oceanic-Oceanic convergence


  Type of collision between two oceanic crustal plates.
• Continental-Continental coonvergence


  Type of collision, two continental crustal plates move toward one another.
• Geological events of Divergent Plate Boundary:

  1. When there is a crack in the continental crust, it creates a rift valley or the splitting of the continental crust.
  2. Mid-Ocean ridge created in the oceanic crust
  3. Earthquakes, if the rift would be wider and wider away, it would be filled up with water. In places where molten lava fill up, Volcanic Islands can be formed.
• Continental and Oceanic plates Geological events in order:


  1. Occurence of Subduction
  2. Subduction zone
  3. Formation of Trench
  4. Volcanic arc
  5. Earthquake caused by the grinding of two plates.
• Oceanic and Oceanic convergent plate boundaries:


  1. The denser oceanic plates subducts
  2. Subduction zone
  3. Formation of trenches
  4. Earthquakes
  5. Formations of Volcanic arcs
  6. Trench will flick upwards causing a Tsunami
• Findings that support sea floor spreading:

  • Rocks are younger at the mid-ocean ridge
  • Rocks farther form the mid-ocean ridge are older
  • Sedimentary rocks are thinner at the ridge
  • Rocks at the ocean floor are younger than those at the continental crust
• Transform plate boundary event:

  1. Fault - constant grinding will cause
  2. Shallow Earthquake - the deeper the fault, the stronger the earthquake
• Subduction zone 


  Process at which the oceanic crust sinks down the continental and goes back to the mantle.
• Pangaea is dubbed as the supercontinent.
• Panthalassa is the water surrounding the Pangaea and it is dubbed as the superocean
• Contracting Earth Theory


  Geophysical theory by James Dwight Dana explaining the cooling and contraction of the Earth's surface.
• Long ago, the Earth's surface was primary composed of molten rock. As time progressed, the surface eventually cooled and contracted, causing the crust to buckle.
• Evidences of the Continental Drift theory:

  • Geologic Evidence
  • Fossil Evidence
  • Climatic Evidence
• Geologic Evidence:

  • Landmasses of Europe, Africa, and Asia fit together like puzzles
  • Similarities between layers of rock and mountain ranges across continents
• Fossil Evidence:

  • Fossils of the same species were scattered across the continents.
• Climatic Evidence:

  • Ancient climate patterns such as glaciers near the equator, tropical coral reefs, and coal swamps near cold areas.