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Physical Geography Tidbits: Oceania

Physical Geography Tidbits: Oceania. Formation of Oceania Islands. Reason for Movement. Excess heat from radioactive decay creates liquid outer core (and magnetic field), and forces mantle to have convection. Exactly how mantle moves?. ASU view. Stream Systems on Dynamic Earth.

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Physical Geography Tidbits: Oceania

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  1. Physical Geography Tidbits: Oceania

  2. Formation of Oceania Islands

  3. Reason for Movement Excess heat from radioactive decay creates liquid outer core (and magnetic field), and forces mantle to have convection

  4. Exactly how mantle moves? ASU view

  5. Stream Systems on Dynamic Earth 3 TYPES OF PLATE INTERACTION

  6. New Zealand - 2 of the 3

  7. Mid Atlantic Ridge East Pacific Rise Mid Indian Ridge

  8. Millions of years before present

  9. Island Arcs from Ocean-Ocean Convergence

  10. Trench Island arc

  11. Older colder ocean plate subducts

  12. Convergence & Tsunami

  13. Effects Of Plate Locking

  14. EQ (or landslide or volcanic eruption ) Movement Generates the Wave that travels about 500 mph

  15. Animated gif

  16. Mega-Quake Set off 2004 Tsunami & will happen again Energy ripple

  17. Sumatra Uplift Sri Lanka

  18. Indonesia

  19. Indonesia

  20. Has Happened, Will Happen Again Chile EQ generated Tsunami that destroyed Hilo in 1960 Hilo, 1960

  21. Hot Spots Focus here on Hawaii & Oceania Often in the middle of a plate

  22. Hawaiian Hotspot

  23. Hawaii - also example of isostacy

  24. Trail of the Hot Spot Note change in direction 43 myr ago Change in direction 43 myr ago

  25. Are plumes real?

  26. Alternative Hypothesis

  27. After Formed … Sink

  28. This NOAA animation shows the dynamic process of how a coral atoll forms. Corals (represented in tan and purple) begin to settle and grow around an oceanic island forming a fringing reef. It can take as long as 10,000 years for a fringing reef to form. Over the next 100,000 years, if conditions are favorable, the reef will continue to expand. As the reef expands, the interior island usually begins to subside and the fringing reef turns into a barrier reef. When the island completely subsides beneath the water leaving a ring of growing coral with an open lagoon in its center, it is called an atoll. The process of atoll formation may take as long as 30,000,000 years to occur. http://www.oceanservice.noaa.gov/education/kits/corals/media/supp_coral04a.html

  29. Fringing Reef Grand Cayman Is. Holand Island

  30. Oeno, Fringing Reef Tureia, Coral Atoll

  31. Bora Bora Atoll

  32. Climate: What would you expect? Realm of the Intertropical Convergence Zone

  33. Hadley Cell Ascending moist aircondenses & rains ITCZ Descendingwarms & dries In subtropics Descendingair warms & dries in subtropics Trade winds Trade winds 0º Equatorial & Tropical Latitudes influenced by ITCZ Desertzone Desert Zone

  34. Global Circulation Patterns Hadley Cell

  35. Little Seasonal Change in Temp

  36. Soils of the Tropics Soils form over tens of thousands of years Gives you a “map” of the “average” location of rainforests & savanna Synonym: Oxisol Soils

  37. Process of Latosol or Oxisol Soils

  38. Laterization soil development Oberlander & Muller, 1984 Soil Name Oxisol Latosol (synonyms in different classifications) Clay type (kaolinite) Not hold nutrients

  39. Oxisol Profiles • Little organic matter • Red from iron oxides • Loose & friable texture

  40. Paradox: Poor soils because few nutrients, yet great rainforests Why? Natural nutrient recycling

  41. With Deforestation • organic matter leached • nutrients lost • Gradual loss of fertility

  42. With deforestation • soil structure hardened by desiccation and compaction into laterite • Can make “laterite” by drying out the soil

  43. Deforestation has always occurred: traditional swidden (slash and burn)agriculture – burn to release nutrients and move to another plot

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