LESSON 9 GEOLOGY

• Continental Drift


  Originally speculated by Dutch cartographer Abraham Ortelius in 1596. It was further developed by Alfred Wegener in 1912.
• Alfred Wegener


  he proposed that modern-day continents once fitted into a single, massive super-continent called Pangaea (or Pangea).
• Evidences for Continental Drift


  Jigsaw fits for some continents
• Biological evidences


  • Matching fossils on continents now located thousands of kilometers apart.
• Evidences for Continental Drift


  Matching geologic structures including mountain chains, ore deposits, and rocks having same features, and age.
• Evidences for Continental Drift


  Climate change evidence, such as glacial deposits at the present-day equator, fossilized palm trees in Greenland
• mid ocean ridges.


  • World War II submarines using SONAR found mountains under the oceans, called
• Dr. Harry Hess from Princeton University in 1962.


  Sea floor drilling showed rocks younger than expected and youngest towards the center of the mid-ocean ridge suggested by ______
• theory of Sea Floor Spreading


  •Occurs at mid-ocean ridges. •New oceanic crusts are formed through volcanic activity, and then gradually moves from the ridge, effectively pushes away older rocks from the ridge.
• Oceanic crust


  is mainly basalt and dolerite, usually 5-10 km thick, forming all the ocean floors. It is created and destroyed at the plate boundaries.
• Continental crust


  is mainly granite and gneiss, some 20-80 km thick, of lower density than oceanic crust. It forms all the continents, submerged continental shelves and adjacent islands.
• Plate Boundaries


  Tectonic plates currently exist on the earth's surface with roughly definable boundaries.
• Transform plate boundaries (conservative)

  are margins where two plates grind past each other without the production or destruction of the lithosphere
• Divergent plate boundaries (constructive)


  are margins where two plates slide apart from each other
• Convergent plate boundaries (destructive)


  also known as active margins, are margins where two plates slide toward each other, to form either of the following
• Subduction zone


  when one plate moves underneath the other
• Continental collision


  when two plates stitched or "sutured" together
• Major plates


  category of tectonic plates - having more than 20M km2 area
• Minor plates


  category of tectonic plates - less than 20M km2 but greater than 1M km2
• Microplates


  category of tectonic plates - less than 1M km2
• 1. Somali Plate 2. Nazca Plate 3. Philippine Plate 4. Arabian Plate 5. Caribbean Plate 6. Cocos Plate 7. Caroline Plate 8. Scotia Plate 9. Burma Plate 10.New Hebrides Plate


  minor plates - dictate atleast 5
• lithosphere.


  Plates are made of rigid ______
• Ocean ridges


  are continuous elevated zones on the floor of all major ocean basins. The rifts at the crest of ridges represent divergent plate boundaries
• Rift valleys


  are deep faulted structures found along the axes of divergent plate boundaries. They can develop on the sea floor or on land.
• Oceanic-oceanic subduction zones


  it happens when two oceanic slabs converge and one descends beneath the other. This produces volcanic island arcs as volcanoes emerge from the sea.
• Continental-continental subduction zones


  it happens when subducting plates contain continental material, or when two continental plates collide. This produces mountain ranges
• •Earthquake patterns

  •Ocean drilling

  •Hot spots


  Evidences for Plate Tectonics
• hot spot


  is a concentration of heat in the mantle capable of producing magma, which rises to earth's surface