1.3 What are the major internal forces and processes, and the resulting landforms?

1. 1.3 What are the majorinternal forces and processes, and the resulting landforms?

2. How do plate movements shape the land? Internal forces (compressional, tensional and lateral forces) Convection currents Plate movements These will be the focus of this Unit. Internal processes Folding Landforms Faulting Vulcanicity

3. What is folding? How does compressional force affect rocks? How does compressional force affect rocks? What internal force does the experiment simulate? 1-3-1e.mpg NSS eBook: 01_e_movie_02.mpg (Modify CertGeog 1.2_01e.mpg) Compressional force. Rocks are folded up under compressional force. Please click above for footage

4. What is folding? The process by which rock layers are folded up undercompressional force is called folding. Let’s study the structure of a fold. Syncline(downfold) Anticline(upfold) Trough Crest Axial plane Limbs Compressional force Compressional force

5. 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

6. 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

7. What is folding? An example of fold

8. What is folding? What landform does folding form? What is the relationship between fold mountains and plate boundaries? Folding develops parallel ranges of mountains. They are known as _______________. fold mountains Rockies Alps Atlas Mountains Himalayas Andes All fold mountains are found at( constructive / destructive ) plate boundaries, where compressional force occurs.

9. What is faulting? What will happen when forces act on fractured rocks? Please click above for footage

10. Fault plane Fault (the crack along which rocks are displaced) Relative movement What is faulting? Faulting occurs when rocks at both sides of a crack are displaced horizontally or vertically Horizontal displacement Vertical displacement

11. Relative movement What is faulting? There are three types of faults. Lateral force Compressional force Tensional force The block is pushed up along the fault plane Two adjacent blocks slide past each other The block slides down the fault plane Tear fault Normal fault Reverse fault

12. Drag the listed fault types and internal forces into the correct boxes. What is faulting? Let’s revise what we have learned about faults. If the game cannot work properly, click here to download the latest Adobe Flash Player.

13. What is faulting? An example of fault

14. What is faulting? What landforms does faulting form? Block mountains (Horsts) Faulting Rift valleys (Grabens)

15. What is vulcanicity? Why does the soft drink spill out of the can? What internal force does this experiment simulate? Please click above for footage

16. What is vulcanicity? Pressure of magma is released. Magma rises through the crust along cracks. Vulcanicity Cracks extend downward and reach the magma chamber Cracks develop in the crust Magma beneath the crust is under great pressure in the crust Magma flows from the asthenosphere to the magma chamber

17. What is vulcanicity? There are two types of vulcanicity. Vulcanicity Intrusive vulcanicity Extrusive vulcanicity

20. The Alps Many of the highest mountains in the world are formed by the folding of sedimentary rocks (Credit: Tom Bean/Corbis) Sedimentary rocks are formed by the accumulation of sediment in the sea, therefore fossils of sea creatures are often found in fold mountains

21. Relative movement Block mountains (Horsts) Block mountains or horsts are flat-top mountains formed between two faults. Example: The Black Forest in Germany They can be formed by both compressional and tensional forces. Rocks may be eroded away Block mountain Compressional force Central block is uplifted

22. Relative movement Block mountains (Horsts) Block mountains or horsts are flat-top mountains formed between two faults. Example: The Black Forest in Germany They can be formed by both compressional and tensional forces. Block mountain Tensional force Side blocks sink

23. Relative movement Rift valleys (Grabens) Rift valleys or grabens are flat-bottom valleys produced between two faults. Example: Rhine Rift Valley They can be formed by both compressional and tensional forces. Rocks may be eroded away Rift Valley Compressional force Side blocks are pushed up

24. Relative movement Rift valleys (Grabens) Rift valleys or grabens are flat-bottom valleys produced between two faults. Example: East African Rift They can be formed by both compressional and tensional forces. Rift Valley Tensional force Blocks are pulled away from each other. Central block sinks

25. What is vulcanicity? Intrusive vulcanicity 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. Please click above for animation

26. Dyke Bedding plane Sill What is vulcanicity? • ________-shaped feature • Parallel to the bedding plane Intrusive vulcanicity Dome • ________-like feature • Vertical or tilted wall Laccolith • ________-shaped chamber • Formed deep underground Dome • ________-like feature • Parallel to the rock layers Sheet Batholith

27. 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. The pressure of the rising magma is ( small / great ). The magma that reaches the earth’s surface is called lava. Why does magma eject from the crust?

28. What is vulcanicity? Extrusive vulcanicity Extrusive vulcanicity is divided into two types. Vent eruptions: Volcanoes Fissure eruptions: Lava plateaux

29. Dykes A dyke in Namibia in southern Africa (Credit: M. Lohmann/Blickwinkel)

30. Eruption of rock debris, fragments, ash, steam and gas Eruption of rock debris, fragments, ash, steam and gas Crater Crater Layers of volcanic materials Vent Parasitic cone Landforms developed from vent eruptions: Volcanoes 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. Magma chamber Volcanic eruption of Mount St Helens, the USA

31. Secondary cone or conelet Volcanic island Landforms developed from vent eruptions: Volcanoes A volcano will develop other features with time. Minor eruptions at the vent produce small volcanoes called secondary cones or conelets. When they form in crater lakes, they become volcanic islands. A crater

32. Crater lake The former cone Solidified lava Landforms developed from vent eruptions: Volcanoes A volcano will develop other features with time. Violent eruptions may blow off the top of the volcano. A large depression, called a caldera, is formed. Caldera Watch a video clip of Crater Lake, North America Please click to browse online Cooled magma

33. 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. Watch a video clip of the fissure eruption at Kilauea, Hawaii Please click to browse online Lava flows in a sheet form, forming ______ ______ lava flow Sheets of lava pile up, forming a ______ _________ Lava flow Example: Deccan Plateau, India lava plateau