tectonic plates

• Oceanic-oceanic convergent plate boundaries occur when two oceanic plates collide, leading to the formation of volcanic island arcs.
• Transform plate boundaries occur where two plates slide past one another, earthquakes and right-lateral strike-slip faults form along these boundaries.
• Convergent plate boundaries occur where two plates collide, the lighter plate is forced below the denser plate forming deep ocean trenches.
• Divergent plate boundaries occur where two plates move apart, magma from below rises to the surface forming mid-ocean ridges.
• There are seven major tectonic plates on Earth, including the North American Plate, South American Plate, African Plate, Eurasian Plate, Antarctic Plate, Indo-Australian Plate, and Pacific Plate.
• Tectonic plates are the outermost layer of the earth's lithosphere, which includes both the crust and upper mantle.
• Transform plate boundaries occur where two plates slide past each other horizontally without any deformation at their boundary.
• Continental-continental convergent plate boundaries are rare but can form due to the collision of continents or the subduction of one continent under another.
• Oceanic-continental convergent plate boundaries occur when an oceanic plate collides with a continental plate, resulting in the formation of mountain ranges and volcanic activity.
• The lithosphere consists of rigid blocks called plates that move over the asthenosphere due to convection currents within the mantle.
• Destructive plate boundary occurs at subduction zones where one plate dives beneath another into the mantle.
• Plates move about 10 cm per year relative to each other.
• Sea floor spreading is the process by which molten rock rises up between two plates, cools and solidifies, forming new seafloor.
• Preserved plate boundary forms as plates move away from each other, leaving no visible evidence on Earth's surface.
• Types of convergent boundaries

  • Oceanic and continental lithosphere
  • Oceanic and oceanic lithosphere
  • Continental and continental lithosphere
• Oceanic and continental convergent boundaries

  1. Oceanic crust subducts underneath the continental crust

  2. Oceanic lithosphere collides with the continental crust, abducts underneath, sinks, magma is formed, rises to the surface, may form volcanic mountains, earthquakes may occur, deep trenches may be formed
• Oceanic and continental convergent boundaries


  • Example: Nazca plate subducts underneath the South America plate, Atacama Trench formed in the ocean, volcanic mountain range like the Andes on land
• Oceanic and oceanic convergent boundaries


  Older oceanic crust subducts underneath younger crust, magma rises to the surface, volcanic island arcs may be formed
• Oceanic and oceanic convergent boundaries


  • Example: North American plate subducts underneath the Pacific Ocean plate, Aleutian Islands created from this collision
• Continental and continental convergent boundaries

  Both crusts do not subduct, no magma or earthquakes occur, plates buckle and create folded mountains
• Continental and continental convergent boundaries

  • Example: Indian plate collides with the Eurasian Plate, creating the Himalayan mountain range
• Faults are formed due to the movement of tectonic plates and the resultant stresses that cause rocks to fracture along planes of weakness. These fractures allow movement between rock blocks, leading to the formation of faults.
• Transform boundaries


  The sliding motion of plates past each other
• Earthquakes occur at transform boundaries due to the sliding motion of plates past each other
• Stresses build up

  1. As plates move

  2. When the stress exceeds the strength of the rocks

  3. They suddenly slip along the fault plane

  4. Generating an earthquake
• Convergent boundaries


  Where plates collide
• Earthquakes are common at convergent boundaries due to intense compressional forces
• Subduction

  1. One plate is forced beneath another

  2. Rocks are subjected to immense pressure

  3. Causing them to fracture and generate earthquakes
• Divergent boundaries


  Where plates move apart
• Earthquakes occur at divergent boundaries as the crust stretches and fractures
• Earthquakes at divergent boundaries are typically less intense than those at convergent boundaries but can still cause significant shaking</b>
• Normal faults


  Forming as the crust pulls apart