Geography notes for F.6

1. Geography notes for F.6 • Natural Landscape

2. What is geomorphology? • It is the study of the origin and evolution of landforms on the earth’s surface . • Most of the earth’s landforms are created mainly by tectonic or endogenic forces (內在) operating in the earth’s crust.

3. Continental Drift • Alfred Wegener,published a book on continental drift in 1915. • His idea is widely accepted into the theory of plate tectonics

4. Evidence of continental drift • Geometric matching of continental borders (like jigsaw puzzle)

6. Geological evidence - the form and pattern of the ancient fold mountains - evidence yielded by rocks - belt of Mesozoic basalt (it can be find everywhere)

7. c) Biological evidence - diverse and specialised groups on various continental fragments

8. d) Palaeoclimatic evidence (史前氣候因素) • fossils found in conditions seem impossible - coal was found in Antarctica

9. e)Palageomagnetic evidence (古地磁學) - Palaeomagnetism is the study of earth magnetism during the geological past

10. - minerals sensitive to the magnetic field align themselves to the earth’s magnetic pole when it cooled and solidified

11. 2. Seafloor spreading • It provide an explanation for continental drift • mid-oceanic ridge is formed • Evidence : Heat flow with minerals, young ocean floor and palaeomagnetic evidence

12. Examples of moving plate

13. The first ship used for geological study

14. Modern ship used for geological survey

15. 3. Plate tectonic • It is a theory combining the concepts of continental drift and seafloor spreading • It is divided into a number of plates “floating” on the asthenosphere • Volcanic and earthquake zones are confined to the plate boundary • The growth of new lithosphere below the ocean is balanced by the destruction of the lithosphere along the convergent boundaries

16. Causes of plate movement • Convection Currents • it is fuelled by radioactive process in the mantle • Difference heating in rock cause rising-sinking motions • It cause a dragging force on the lithospheric plate

18. The mechanism • all continents once formed one supercontinent called PANGAEA (聯合古陸) • It split into Laurasian and Gondwanaland

20. B Internal structure of the earth • Earth has a diameter of 6370 km and about 40000km in circumference • It consist of a solid crust (about 6km beneath the oceans and 35-40 km under mountains ) • A solid mantle(about 3000km thick) • A core (solid inner core and liquid outer core)

22. Materials in the earth crust

23. Moho (Mohorovicic Discontinuity)(莫霍界面) • The thickness of the earth is found by a Yugoslavian scientists ,Andrija Mohorovicic • It is the abrupt change (突然轉變)in density between the crust and the mantle • This boundary zones averages about 10 km below sea level in oceans basin and and about 30 km beneath high mountains

24. Some important terms • The mantle is much hotter than the crust .It compose of mineral olivine. • The density is 5g/cm • The inner core is solid while the outer core is liquid • Lithosphere is the crust and rigid uppermost parts of upper mantle,at a depth of about 100km • Asthenosphere (軟流圈)is a zone of weaker and more plastic rocks and extend to 240km

25. Waves • When an earth tremor(震動),primary and secondary waves are transmitted through the epicentre (震央),the point at which the earthquakes occur • Primary waves travel through solids and liquid while secondary waves travel through only solids

26. A. Constructive plate margin • It is a boundary where two plates move apart. A fissure develops,allowing hot ,molten rock to well up from the mantle and to from new materials as it solidifies,the fissure is called a spreading,or “pull apart” centre.

27. Mid-oceanic ridge map by computer

28. Mauna Loa in Hawwii

29. Erta Ale in East Africa – an active zone of rift valley

30. Mid- Atlantic ridge is a good example • It will cause volcanic activity, Iceland and the Azores • High magnitude volcanic eruptions on and around the ridges,volcanic island produced

32. B. Destructive plate margin • It is a boundary where two plates collide. The more dense plate will normally be deflected beneath the less dense plate,and will be destroyed and absorbed at depth. • Such action take place at the zone of subduction. Crumped (摺曲、扭曲) mountain ranges,volcanoes earthquakes and ocean trenches (海溝)are found

33. Andes Mountain – a type of destructive plate boundary

34. Three types of collision • Collision between oceanic plate and continential plate

35. Collision between oceanic plates

36. Collision between continental plates

39. The moving path of Indian plate

40. Conservative plate margin • It is also called transform fault

41. The formation of transform fault

43. San Andrea’s fault

44. Plate tectonics and Man • The existing features of the continents and ocean basins are explained by the theory of plate tectonic • Produce environmental hazards: volcanic eruptions and earthquakes • Produce mineral resources

45. Ring of Fire

47. Earthquakes • Magnitude of earthquakes refer to the energy released at the source • It is measured by either by Richter Scales (0-8logarithmic scale) (里氏震級表) or Mercalli Scales (12 gradations) • There is no direct relationship between the magnitude and the damage caused in the earthquake

48. Human Response to Earthquakes • Made seismic hazard zone maps for landuse planning • Man-made measure to trigger small earthquakes • Drills and shock-proof buildings are designed • Extensive monitoring of the earthquakes

49. Seismometers (地震儀)are used to detect small earthquake • Tiltmeters (傾斜儀) and electronic distance measurers (電子距離儀) are used to measure the shape of the volcanoes • Fertile soil is produced • Iron,copper,zinc,lead,uranium ,etc

50. Hotspot (熱點)