2. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit 1.3What are the major internal forces and processes, and the resulting landforms?

3. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Internal forces (compressional, tensional and lateral forces) How do plate movements shape the land? Convection currents Plate movements Internal processes Folding Faulting Vulcanicity Landforms These will be the focus of this Unit.

4. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is folding? How does compressional force affect rocks? 1-3-1e.mpg NSS eBook: 01_e_movie_02.mpg (Modify CertGeog 1.2_01e.mpg) Please click above for footage What internal force does the experiment simulate? Compressional force. How does compressional force affect rocks? Rocks are folded up under compressional force.

5. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Syncline (downfold) Anticline (upfold) Axial plane Trough Crest Limbs The process by which rock layers are folded up under compressional force is called folding. Let’s study the structure of a fold. What is folding? Compressional force

6. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is folding? What will happen when the compressional forces from both sides are equal in strength? The gradient on both sides:  the same  different The axial plane of fold:  tilted  vertical

7. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is folding? What will happen when the compressional forces from both sides are unequal in strength? The gradient on both sides:  the same  different The axial plane of fold:  tilted  vertical

8. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is folding? An example of fold

9. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is folding? What landform does folding form? Folding develops parallel ranges of mountains. They are known as _______________. fold mountains What is the relationship between fold mountains and plate boundaries? Atlas Mountains Alps Himalayas Rockies Andes All fold mountains are found at ( constructive / destructive ) plate boundaries, where compressional force occurs.

10. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is faulting? What will happen when forces act on fractured rocks? Please click above for footage

11. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Relative movement What is faulting? Fault plane Fault (the crack along which rocks are displaced) Vertical displacement Horizontal displacement Faulting occurs when rocks at both sides of a crack are displaced horizontally or vertically

12. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Normal faultReverse fault Tear fault What is faulting? There are three types of faults. Relative movement The block slides down the fault plane Two adjacent blocks slide past each other The block is pushed up along the fault plane Tensional force Lateral force Compressional force

13. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is faulting? If the game cannot work properly, click here to download the latest Adobe Flash Player.click here Let’s revise what we have learned about faults. Drag the listed fault types and internal forces into the correct boxes.

14. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is faulting? An example of fault

15. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is faulting? What landforms does faulting form? Faulting Block mountains (Horsts) Rift valleys (Grabens)

16. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? Please click above for footage Why does the soft drink spill out of the can? What internal force does this experiment simulate?

17. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Magma beneath the crust is under great pressure in the crust What is vulcanicity? Magma flows from the asthenosphere to the magma chamber Cracks develop in the crust Cracks extend downward and reach the magma chamber Pressure of magma is released. Magma rises through the crust along cracks. Vulcanicity

18. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? There are two types of vulcanicity. Vulcanicity Intrusive vulcanicity Extrusive vulcanicity

19. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit

20. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit

21. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Many of the highest mountains in the world are formed by the folding of sedimentary rocks Sedimentary rocks are formed by the accumulation of sediment in the sea, therefore fossils of sea creatures are often found in fold mountains The Alps (Credit: Tom Bean/Corbis)

22. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Block mountains (Horsts) Block mountains or horsts are flat-top mountains formed between two faults. They can be formed by both compressional and tensional forces. Compressional force Block mountain Rocks may be eroded away Relative movement Example: The Black Forest in Germany Central block is uplifted

23. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Block mountains (Horsts) Block mountains or horsts are flat-top mountains formed between two faults. Tensional force They can be formed by both compressional and tensional forces. Example: The Black Forest in Germany Side blocks sink Block mountain Relative movement

24. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Rift valleys (Grabens) Rift valleys or grabens are flat-bottom valleys produced between two faults. They can be formed by both compressional and tensional forces. Compressional force Relative movement Rift Valley Rocks may be eroded away Example: Rhine Rift Valley Side blocks are pushed up

25. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Rift valleys (Grabens) Rift valleys or grabens are flat-bottom valleys produced between two faults. They can be formed by both compressional and tensional forces. Example: East African Rift Tensional force Relative movement Rift Valley Blocks are pulled away from each other. Central block sinks

26. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? Intrusive vulcanicity Please click above for animation Intrusive vulcanicity refers to the process by which magma enters _________ or __________ in the crust from the asthenosphere. cracks chambers When magma cools and solidifies in the crust, intrusive volcanic features are formed.

27. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? Intrusive vulcanicity Laccolith Batholith Sill Dyke Bedding plane ________- shaped feature Parallel to the bedding plane Dome ________-like feature Vertical or tilted wall ________-like feature Parallel to the rock layers Sheet ________- shaped chamber Formed deep underground Dome

28. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? Extrusive vulcanicity Extrusive vulcanicity refers to the process by which the rising magma ejects from the crust through a vent or a fissure. Why does magma eject from the crust? The pressure of the rising magma is ( small / great ). The magma that reaches the earth’s surface is called lava.

29. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit What is vulcanicity? Extrusive vulcanicity Extrusive vulcanicity is divided into two types. Vent eruptions: Volcanoes Fissure eruptions: Lava plateaux

30. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Dykes A dyke in Namibia in southern Africa (Credit: M. Lohmann/Blickwinkel)

31. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Layers of volcanic materials Magma chamber Vent Parasitic cone Crater When lava erupts through these cracks, a small cone at the side of the main cone may form. This cone is called a parasitic cone. Eruption of rock debris, fragments, ash, steam and gas Landforms developed from vent eruptions: Volcanoes Eruption of rock debris, fragments, ash, steam and gas Crater Volcanic eruption of Mount St Helens, the USA

32. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Landforms developed from vent eruptions: Volcanoes A volcano will develop other features with time. A crater Minor eruptions at the vent produce small volcanoes called secondary cones or conelets. Secondary cone or conelet When they form in crater lakes, they become volcanic islands. Volcanic island

33. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Landforms developed from vent eruptions: Volcanoes A volcano will develop other features with time. Solidified lava Caldera Crater lake The former cone Cooled magma Violent eruptions may blow off the top of the volcano. A large depression, called a caldera, is formed. Watch a video clip of Crater Lake, North America Please click to browse online

34. © Oxford University Press 2009 Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Quit Landforms developed from fissure eruptions: Lava plateaux A fissure eruption refers to the process by which  lava erupts from the crust through a vent.  lava wells out through a crack or a fault on a surface. Lava flows in a sheet form, forming ______ ______ lavaflow Sheets of lava pile up, forming a ______ _________ Lava flow lavaplateau Example: Deccan Plateau, India Watch a video clip of the fissure eruption at Kilauea, Hawaii Please click to browse online