Edexcel AS Geography

1. Edexcel AS Geography Unit 1 – Global Challenges Topic 1 – World at Risk Global Hazard Patterns

2. Hazard Risk in Your Local Area • Looking at disaster hotspots shows that some places are at more risk than others • California and the Philippines suffer from multiple hazards, but you need to think about places closer to home • In the exam, the examiners may ask you about real or potential hazard risk in your local area.

3. Hazard Risk in Your Local Area • You need to be able to talk about: • Any past events that might have happened in the area you live, e.g. droughts that have occurred • Any likely future events that could happen, e.g. Landslides caused by coastal erosion • The impact of these events on people, property and the environment

4. Hazard Risk in Your Local Area • Researching the history of hazard events in your local area could be done by: • Researching historic newspapers • Searching online • Interviewing older residents • Research the 4 main hazards faced by this area (Attiki, Greece)

5. Greece deaths Disaster Date No Killed • Extreme temperature 20/7/1987 1000 • Earthquake 12/8/1953 455 • Earthquake 7/9/1999 143 • Earthquake 1928 103 • Wildfire 24/8/2007 67 • Extreme temperature 3/7/1988 56 • Earthquake 20/6/1978 50 • Volcano July 1956 48 • Storm March 1987 48 • Storm Νοvember 196143 • Source: "EM-DAT: The OFDA/CRED International Disaster Database www.em-dat.net - Université Catholique de Louvain - Brussels - Belgium"

6. Greece affectedDisaster Date No Total Affected • Earthquake 20/6/1978 600100 • Earthquake 7/9/1999 115139 • Earthquake 24/2/1981 80400 • Earthquake 13/9/1986 45300 • Earthquake 9/3/1965 30253 • Earthquake may 1967 16583 • Earthquake 1/9/1966 15123 • Earthquake 13/5/1995 15060 • Earthquake 15/6/1995 13900 • Earthquake 5/2/1966 11050       Source: "EM-DAT: The OFDA/CRED International Disaster Database www.em-dat.net - Université Catholique de Louvain - Brussels - Belgium"

7. Greece monetary lossesDisaster Date Damage (000 US$) • Earthquake 7/9/1999 4200000 • Wildfire 24/8/2007 1750000 • Drought March 1990 1000000 • Earthquake 24/2/1981 900000 • Earthquake 13/9/1986 745000 • Wildfire June 1998 675000 • Flood 2/2/2003 600000 • Earthquake 13/5/1995 450000 • Flood 24/10/1994 437700 • Earthquake 15/6/1995 422700       Source: "EM-DAT: The OFDA/CRED International Disaster Database www.em-dat.net - Université Catholique de Louvain - Brussels - Belgium"

8. Attiki natural disasters • Choose 4 disasters for Attiki and research them to produce some fact files for our local area. You could choose... • Droughts • Earthquakes • Floods • Wild fires Or any others you think are interesting! Remember to cover the impact of these events on people, property and the environment. Also..Which hazard event is most likely to be repeated? How do you rate the risks of such an event?

9. Hazard Distribution – Geophysical • Geophysical hazards (especially volcanoes, earthquakes and to some extent tsunamis) usually occur near plate boundaries so knowledge of plate tectonics in required.

11. Platetectonics • The lithosphere (the Earth’s crust and the rigid upper part of the mantle) is divided into 7 large and several smaller plates. • The plates, which are rigid, float like rafts on the underlying semi-molten mantle (called the asthenosphere) and are moved by convection currents. • Convection currents are generated by hotspots within the asthenosphere which cause magma (molten material) to rise towards the earth’s surface. • These currents can cause the plates above to move together, apart or side by side.

13. Crust • Plates are made of two types of crust: • Continental crust – is composed of older, lighter (less dense) rock of a granitic type • Oceanic crust - is composed of much younger, denser rock of a basaltic composition.

14. Hazard Distribution – Geophysical • Volcanoes and earthquakes most commonly occur at the boundaries where the plates meet. • There are three types of plate boundary – constructive, destructive and conservative. • The type of movement and the degree of activity at the plate margins almost totally controls the distribution, frequency and magnitude of earthquakes and volcanic eruptions.

15. Hazard Distribution – Earthquakes

16. Earthquakes • The main earthquake zones are clustered along plate boundaries. • The most powerful earthquakes are associated with destructive or conservative plate boundaries

17. Destructive Plate Boundaries

18. Destructive Plate Boundaries – plate converge 1. An oceanic plate and a continental plate move towards each other • Eg Alongside South America is the Nazca Plate (oceanic ) and the American Plate (continental) • Also the Philippines • The oceanic plate is forced downwards as it is denser than the continental plate • This results in a subduction zone • An ocean trench forms too – (where the sea water is deeper here) • Friction occurs and the force of the compression as the plates meet causes stresses in the crust and pressure occurs as the oceanic plate subducts • When the pressure is released the point at which it is released is called the focus • The ground surface immediately above shakes • The point on the surface where the maximum damage occurs is the epicentre • The oceanic plate breaks off and melts over a long time period • Newly formed magma rises at the continental plate and forms volcanoes and fold mountains eg Andes

19. Destructive Plate Boundaries • 2. The same process occurs where two plates of oceanic crust are moving towards each other • The denser of the two will be subducted • e.g. This has formed the volcanic islands of Indonesia. • As one plate moves under the other they can get stuck. This causes pressure to build up. • When the pressure becomes too much the plates jerk past each other, causing an earthquake. • Sometimes the magma rises offshore to form an island arc of volcanic islands eg Caribbean islands and Japan

20. Ocean-ocean convergence

21. Continental-continental convergence

22. Destructive Plate Boundaries 3. Collision - Two continental plates move towards each other • They are of equal density so there is no subduction • The rocks are forced upwards to form fold mountains • Eg The Indian and Eurasian plates are moving together forming the Himalayas and Mount Everest is slowly growing • Earthquakes occur in these locations • eg Large areas of countries can be affected by these shallow highly damaging earthquakes eg India and Iran • There is no volcanic activity in these locations • The Kashmir earthquake of 2005 occurred in this way.

23. Constructive Plate Boundary

24. Constructive Plate Boundaries • Both volcanoes and earthquakes occur at constructive plate boundaries • Two plates move away from each other (diverge) due to convection currents in the asthenosphere • Molten magma rises to fill the gap and forms new oceanic crust through volcanic activity • Eg North American plate is moving away from Eurasian plate so Atlantic ocean is getting 3cm larger – USA and Europe are moving apart • Mid oceanic ridges are formed eg The Mid Atlantic Ridge • Islands may be visible above the water’s surface as islands eg Iceland • Earthquakes occur here due to friction and pressure release. • There are many earthquakes here. These earthquakes tend to be shallow and low magnitude as lava rises. • Most (not Iceland!) tend to be under the sea so pose little hazard to humans. • The plates do not move apart in a uniform way – some parts move faster than others. This causes pressure to build up. When the pressure becomes too much, the plate cracks, making a fault line and causing an earthquake. Further earthquakes may also occur along the fault line once it has been created.

25. Constructive/Divergent

26. Conservative/Transform Plate Boundary

27. Conservative Plate Boundaries • Earthquakes also occur at Conservative boundaries • A conservative boundary occurs where two plates are movingpast each other laterally • The two plates get locked together in places and pressure builds up. As with destructive boundaries, this causes the plates to jerk past each other (or to crack forming fault lines) releasing the energy as an earthquake • For example, the Pacific plate is moving past the North American plate. • Many earthquakes occur along this boundary and its fault lines, e.g. The San Andreas Fault runs through California. • These earthquakes are often shallow and some are very high magnitude.

29. Other earthquakes • A small minority of earthquakes occur within plates, usually involving the reactivation of ancient faultlines eg Shropshire, UK • Also earthquakes can occasionally occur due to human activity such as dam and reservoir building, which increase the weight and therefore stress on the land. Earthquakes then can happen where there is no record of earthquakes. • Eg Killari, India (1993)10,000 killed by an earthquakes caused by dam construction.

30. Earthquake hazards • Primary hazards – result from ground movement and shaking. The surface waves can cause buildings and infrastructure (like pipelines and roads)to collapse. • Secondary hazards – soil liquefaction, landslides, avalanches, tsunamis and exposure to adverse weather. These increase the death toll. Read p 9-10 Pearson

31. Volcanoes

33. Most of the world’s active volcanoes are at constructive and destructive plate margins as well as hotspots. • However, hazard risk can also come from dormant volcanoes that have not erupted in living memory eg Mt St Helens

34. Constructive boundaries • Constructive plate boundaries – most of the magma that reaches the earths surface wells up as volcanoes at ocean ridges, such as the mid Atlantic ridge. • These volcanoes are mostly on the sea floor and do not represent major hazards except on islands like Iceland. • Rift valleys are also present where continental crust is being stretched eg East African Rift valley has 14 active volcanoes which can produce big explosions.

35. East African Rift Valley

38. The East African Rift is a geological zone where continental plates in Eastern Africa have developed a tectonic plate boundary. A rift is a fracture in Earth's surface that widens over time. • This is a part of the larger Great Rift Valley, where the African Plate is in the process of dividing into two new tectonic plates called the Somali Plate and the Nubian Plate.

39. Destructive boundaries • Destructive plate boundaries – some 80% of the worlds most active volcanoes occur along destructive boundaries. • Soufriere Hills in Montserrat formed when 2 oceanic plates converged. • When oceanic plates are sub ducted beneath continental plates, explosive volcanoes, such as Mt St Helens, are formed. • The ‘Ring of Fire’ around the pacific has many such volcanoes, including those in the Philippines

40. Hotspots • Volcanoes can occur far away from any plate boundaries, e.g. in Hawaii • These volcanoes are thought to be caused by in localised areas of the lithosphere where there is a high heat flow and where magma is rising from a large chamber beneath the crust as a plume. • As a lithospheric plate moves over the hotspot a chain of volcanoes forms. • Areas like Hawaii are called volcanic hotspots

41. Hawaii hotspot

43. Volcanic hazards • Volcanic Hazards – Apart from the local impacts of lava flows the most catastrophic impacts of volcanoes are pyroclastic flows, ash falls, tsunamis and mudflows/lahars. • Read p 10-11 Pearson

44. Hazards: Distribution – Slides Slides include a variety of rapid mass movements – eg rock slides, debris flows, snow avalanches, rainfall and earthquake induced landslides. Land Slides Landslides are the 7th biggest killer with over 1,400 deaths per year, ranking above both volcanoes and droughts. Most places that are vulnerable to landslides are mountainous areas, often after abnormally heavy rain and/or seismic activity. Human factors also play a part. Deforestation of hill sides, eg SE Asia, and building upon hill slopes, eg Hong Kong, are problematic if there are heavy rains.

45. Landslides

46. Snow avalanches • Snow avalanches are concentrated in high mountainous areas such as Rockies of N America, S. Alps of N Zealand. • Avalanches tend to occur on slopes that are more than 35 degrees. • On average 40 deaths occur in Europe and 100 in North America from avalanches. • Recent research has reported that global warming may be increasing avalanche activity. • However trends in deaths have slowed due to better management. Read p 11 Pearson

47. Hydro meteorological Hazards: These extreme weather hazards tend to be more widespread in their distribution . They are growing in frequency. They are increasingly unpredictable in their locations.

48. Drought • Droughts have a dispersed pattern. • Over one third of the earth’s land surface has some level of drought exposure. • This includes 70% of the worlds people and agricultural value. • This means drought has a vast impact on the worlds food security.

50. Causes of droughts • 1. Variations in the movement of the inter tropical convergence zone (ITCZ). As it moves N or S through Africa it brings a band of seasonal rain. In some years high pressure bands expand which block the rain bearing winds. This can lead to famines in Ethiopia where farmers depend on the rains. • 2. E Nino can bring major changes to rainfall patterns. It brings drought conditions to Australia and Indonesia