Science g10

• Plate tectonics


  Consists of crust and the upper portion of the mantle, in constant but slow motion
• Plate tectonics


  • The Arctic Ridge has the slowest rate (less than 2.5 cm/yr)
  • The East Pacific Rise near Easter Island has the fastest rate (more than 15 cm/yr)
• Plates


  Large pieces of the upper few hundred kilometers of Earth that move as a single unit as it floats above the mantle
• Plates


  • In constant motion
  • Important geological processes take place along their margins, such as the formation of mountain belts, earthquakes, and volcanoes
• Lithosphere


  The movement of the lithosphere
• Crust


  • Oceanic crust is thicker but less dense than the continental crust
  • Continental crust floats higher than the oceanic crust
• The Philippine Island is not formed because of the convergence of the Philippine plate and the Pacific plate
• • Some Philippine islands are products of subduction process
  • Mostly are part of the Philippine Mobile Belt, except for Palawan, Mindoro and Zamboanga
  • Originated geologically in an oceanic-oceanic convergence
• The world's earthquakes are not randomly distributed over the earth's surface. They tend to be concentrated in narrow zones
• • Some earthquakes are located near the edges of the continents, some are in mid-continents, while others are in ocean
  • But not ALL edges of continents, mid-continents, or oceans can be places where earthquake might occur
• Large part of the pacific ocean, northernmost Asia, majority of Europe, Eastern portion of North and South America and western Africa are places with no earthquakes
• It is important to identify areas which are prone to earthquakes

  So that necessary precautions could be done if ever you're living in one of those places
• Volcanoes are not randomly distributed. Majority of them are found along the edges of some continents
• Majority of volcanoes are found along the edges of some continents, particularly in the western coast of North and South America, East and South East Asia
• Earthquake epicenters and volcanoes are both situated at the same locations
• Mountain ranges are found in places where volcanoes and/or earthquake epicenters are also located
• Geologic activities such as seismicity (occurrence of earthquake), volcanism and mountain formation are the basis of scientists in dividing the earth's lithosphere
• Plate boundaries


  The places on earth where most of the earthquakes originated or some mountains and volcanoes were formed mark the boundaries of each lithospheric plate<|>Each plate is slowly moving relative to each other, causing geologic events to happen along their boundaries
• Plates


  • In constant motion
  • As they interact along their margins, important geological processes take place, such as the formation of mountain belts, earthquakes and volcanoes
• If you are about to visit a place in the Pacific known to be along converging plates


  You will expect to see: Active Volcanoes, Mountain Ranges, Volcanic Islands
• When crustal plate A is moving away from crustal B, the expected average rate of change in position between A and B is a few centimeter away
• Divergent Boundary


  Wherein plate boundary move apart, creating a zone of tension
• Divergent boundary


  1. Plates are moving apart and new crust is created by magma pushing up from the mantle

  2. Submarine mountain range such as the mid-Atlantic Ridge

  3. Volcanic activity in the form of fissure eruptions

  4. Shallow earthquake activity

  5. Creation of new seafloor

  6. Widening ocean basin
• Divergent boundary between continental plates


  1. Rift valley formation which will soon develop into linear sea

  2. Shallow earthquake activities

  3. Numerous normal faults
• Convergent Plate Boundary


  Wherein plate boundary moving toward each other
• Transform Fault Boundary


  Where plates slide or grind past each other without diverging or converging
• Transform Fault Boundary

  • San Andreas fault which is bounded by the North American plate and the Pacific plate
• Transform-fault boundaries


  • Most are found on the ocean floor
  • Commonly offset active spreading ridges, producing zigzag plate margins
  • Generally defined by shallow earthquakes
• Toward each other


  Plates collide
• Away from each other


  Lithosphere is being pulled apart
• Slide past each other


  Plates move
• Two continental plates in collision

  • Rocks caught in between are squeezed, crumpled, and lifted, mountains are built like the Himalayan Range
• Two oceanic plates in collision

  • One plate dives under the other, the process is called subduction
  • Diving plate will eventually reach a place inside Earth where melting occurs, magma will rise to Earth's surface to form volcanic islands
  • Volcanic islands are always accompanied by trenches
• Trench


  Depression in the ocean floor where one plate is subducting under another plate, the deepest part of the ocean
• Trenches

  • Marianas Trench (east of the Marianas), Philippines Trench (east of the Philippines), Java Trench (south of Indonesia)
• Philippine


  An Island arc
• When two oceanic plates converge

  They undergo subduction process, giving rise to the formation of volcanic island arcs, trenches and generating shallow, intermediate or deep earthquakes
• Strong earthquakes generated at the ocean floor


  May cause displacement of large volume of water and launch big waves called tsunami
• Oceanic and continental plates in collision

  • The oceanic plate being the denser plate subducts or dives under the continental plate, subduction will produce a trench and initiate volcanism
• Divergent boundary


  1. Crust is generated as the plates separate and pull away from each other in a very slow movement

  2. Formation of rift valleys and oceanic ridges

  3. Oceanic ridges and subduction zone are boundaries between plates of lithosphere

  4. When the oceanic lithosphere divides along the ocean ridge, there is a gap created

  5. Gap is filled with magma that rises from the asthenosphere

  6. New materials will slowly cool and solidifies to produce new ocean floor

  7. Rate of spreading along these ridges averages 2.5 cm per year or may vary from 2 to 20 cm per year