Edexcel AS Geography Unit 1 – Global Challenges Topic 1 – World at Risk Global Hazard Patterns.
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Edexcel AS Geography Unit 1 – Global Challenges Topic 1 – World at Risk Global Hazard Patterns
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.
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
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
Attiki natural disasters factfile
Greece deaths Disaster Date No Killed Extreme temperature 20/7/ Earthquake 12/8/ Earthquake 7/9/ Earthquake Wildfire 24/8/ Extreme temperature 3/7/ Earthquake 20/6/ Volcano July Storm March Storm Νοvember Source: "EM-DAT: The OFDA/CRED International Disaster Database - Université Catholique de Louvain - Brussels - Belgium"
Greece affected Disaster Date No Total Affected Earthquake 20/6/ Earthquake 7/9/ Earthquake 24/2/ Earthquake 13/9/ Earthquake 9/3/ Earthquake may Earthquake 1/9/ Earthquake 13/5/ Earthquake 15/6/ Earthquake 5/2/ Source: "EM-DAT: The OFDA/CRED International Disaster Database - Université Catholique de Louvain - Brussels - Belgium"
Greece monetary losses Disaster Date Damage (000 US$) Earthquake 7/9/ Wildfire 24/8/ Drought March Earthquake 24/2/ Earthquake 13/9/ Wildfire June Flood 2/2/ Earthquake 13/5/ Flood 24/10/ Earthquake 15/6/ Source: "EM-DAT: The OFDA/CRED International Disaster Database - Université Catholique de Louvain - Brussels - Belgium"
Attiki natural disasters factfile Our local area has many natural hazards. Earthquakes Droughts Floods Wild fires Cause most of the deaths, injuries, damages etc. We need to think about 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?
1999 earthquake Magnitude of 6.0 Richter Occurred on September 7, 1999, at 2:56:50 pm local time and lasted approximately 15 seconds in Ano Liosia. The tremor was epicentered approximately 17 km to the northwest of the city center, in a sparsely populated area near Mount Parnitha National Park. This proximity to the Athens Metropolitan Area resulted in widespread structural damage,
143 dead 2,000 injured 50,000 homeless 53,000+ buildings damaged or destroyed Northern Athenian suburbs of Kifissia, Metamorfosi, Kamatero and Nea Philadelphia worst affected. More than 100 buildings (including three major factories) across those areas collapsed trapping scores of victims under their rubble while dozens more were severely damaged.
It was the biggest disaster in almost half a century. This event took Greek seismologists by surprise as it came from a previously unknown fault, originating in an area that was for a long time considered of a particularly low seismicity.
Future earthquake risk? Greece has thousands of earthquakes a year (the vast majority extremely mild) The strict building codes are upgraded and reinforced after every major quake and this has given the Greeks a certain quiet confidence in their buildings, which translates into an almost relaxed attitude towards earthquakes. Education pays back - learning how to prepare for earthquakes has been mandatory in all schools for some time.
This ensures that younger generations grow up knowing what to do and they then disseminate the information to their parents and into their local community.
1987 extreme temperatures Summer of 1987 saw a heat wave with temperatures as high as 44 degrees C and low wind speeds 1000 people died in Athens from July – more than double the usual for this period Smog also accompanied the heat wave so made the stress greater for the people Elderly and retired people were particularly susceptible
2960 people were administered to 68 Athens hospitals at this period The deaths were from heat stroke, heat exhaustion etc
2007 wild fires 28 June 2007  - 3 September 2007  A series of massive forest fires that broke out in several areas. The most destructive and lethal infernos broke out on 23 August, expanded rapidly and raged out of control until 27 August, until they were put out in early September. In total 84 people lost their lives because of the fires, including several fire fighters. 8] 8]
Some of these firestorms are believed to be the result of arson while others were indeed the result of mere negligence.   Hot temperatures, that included three consecutive heat waves of over 40 °C, and severe drought rendered the 2007 summer unprecedented in modern Greek history. From the end of June to early September, over 3,000 forest fires were recorded across the nation.
A total of 2,700 square kilometers of forest, olive groves and farmland were destroyed in the fires, which was the worst fire season on record in the past 50 years. Many buildings were also destroyed in the blaze. The fire destroyed 1,000 houses and 1,100 other buildings, and damaging hundreds more. Economic losses of US$ 1.75 billion
The first major fire of the summer of 2007 was started on 28 June It is perceived to have been started by either an exploding electrical pylon or by arsonists. Significant parts of the Parnitha National Park were destroyed and in total, the fire burnt area of km 2 making it one of the worst recorded wildfires in Attica since the Penteli fire of July 1995.
The magnitude of the devastation was unforeseen. Environmental studies in Greece report that the Athenian microclimate will significantly change to warmer during the summer season, and flooding is now a very probable danger for the northern suburbs of the city. Mount Parnitha was considered the lungs of Athens; following its considerable burning, both the city and local flora and fauna are expected to feel the consequences.
24 August NASA
Future risk of fires? Attica is the highest risk zone in Greece The high forest fire risk potential is most probably increasing due to increasing temperatures, decreasing precipitation and consequently rising drought potential caused by climate change It is mainly due to the development dynamics of Athens conurbation – ie further urbanisation.
Athenians are moving back to countryside on the edge of the city so residential areas are intermixed in forestlands. Eg. Penteli 50% urbanised from 1940s -1990s (Varela at all, 1999). Tourism has become a new form of land use, and has in some areas replaced traditional economic activities (farming and grazing). Seasonable employee in tourists activities as well as tourists do not develop an attitude of responsibility towards the land they are visiting (Pyne, 1997).
1994 Greek floods Flooding constituted the second most frequent natural disaster in Greece during 1928–2005 (15 episodes; 23.4% of total) after earthquakes. It led to 78 deaths, 10,990 affected people and 719,518,000 US$ damage and repair costs (World Health Organisation 2005).
Nevertheless, the 28 episodes of flooding in Attica Prefecture cost more human lives (182 people) during the last century 887– 2005) than earthquakes (18 people) while the cost in human lives due to flooding for the whole country during the same period was 220 people
The increase in urbanized area led to concomitant decrease in cultivated, forested and shrub areas (was 81.3% in 1945; 31.0% in 1995). Human interference at suburban areas of Attika included land clearance, agricultural abandonment, forest fires, unplanned expansion of urban areas, and rubble-filing for the creation of roads and plots.
Led to reduction in the infiltration of water And to increase in erosion, surface runoff and locality-specific vulnerability to flash flooding depending on distance from streams and slope of land at Attica basin Spasmodic, un-coordinated mainly reactive flood-prevention strategy, which does not take under consideration the anticipated increase in intensity and rapidity of rainfalls due to climate change at Attika basin
300 mm in 24 hours October (normally 400mm in year) Low pressure depression arrived 9 dead in Athens Extensive damage to some bridges, roads etc
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.
Platetectonics The lithosphere (the Earths 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 earths surface. These currents can cause the plates above to move together, apart or side by side.
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.
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.
Hazard Distribution – Earthquakes
Earthquakes The main earthquake zones are clustered along plate boundaries. The most powerful earthquakes are associated with destructive or conservative plate boundaries
Destructive Plate Boundaries
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
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
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.
Constructive Plate Boundary
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 waters 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.
Conservative/Transform Plate Boundary
Conservative Plate Boundaries Earthquakes also occur at Conservative boundaries A conservative boundary occurs where two plates are moving past 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.
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.
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
Most of the worlds 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
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.
East African Rift Valley
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.
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 Philippinesthe Philippines
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
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 Pearson
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 7 th 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.
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
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.
Drought Droughts have a dispersed pattern. Over one third of the earths 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.
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
3. Changes in mid latitude depressions. In temperate regions like the UK depressions bring rainfall. However if anticyclones (high pressure) form and block the depressions and persist (so they are forced northwards) then very dry conditions may result. This has occurred in the UK and France (1976, , 1995, 2003, 2006) and in the USA midwest in the 1930s (forming the dustbowl in the depression)
Drought hazards Droughts can bring about: Failure of crops Loss of livestock Wildfires Duststorms Famine Population migration – refugees etc Economic impacts (especially in LEDCS) Read p 7-8 Pearson
Flooding Flooding is a frequent hazard and it is evident to some 33% of the worlds area, which is inhabited by some 80% of the worlds population. Regionally, high magnitude events are frequent in India, Bangladesh and China.
Causes of flooding 1. The most common cause is excessive rainfall relating to atmospheric processes, like monsoon rainfall and tropical cyclones. In temperate climates (like Britain) a series of depressions can bring excessive rainfall if heavy and prolonged. 2. Intense rainfall sometimes associated with thunderstorms can result in flash floods which can have a devastating effect.
3. El Nino Southern Oscillation can bring devastating floods – such as in Mozambique in 1997 and Rapid snowmelt can add water to rivers which already have high discharges.
Flood hazards Deaths through drowning and disease Destruction of food crops Loss of homes Loss of infrastructure Damages livelihoods and businesses (MEDCS mainly) High insurance costs (MEDCS) Read p 8-9 Pearson
Storms Includes tropical cyclones, mid latitude storms and tornadoes.
Tropical Cyclones Tropical cyclones are huge storms with strong winds and torrential rain. They are between km in diameter They develop above sea water that is 26°C or higher. As warm, moist air rises and condenses, it releases energy which increases wind speed. Tropical cyclones lose strength when they move over land because the energy supply from the warm water is cut off Most cyclones occur between 5° and 20° north and south of the equator – more than 30° away from the equator the water isnt warm enough for cyclones to occur They tend to move westwards due to the east-west winds in the tropics. For example, the trade winds move tropical cyclones westwards across the Atlantic Ocean towards the Caribbean Sea Cyclones spin because of the Coriolis effect (the force that deflects the path of winds due to the Earths rotation)
Tropical Cyclones Cyclones do not occur 0-5° either side of the equator because the Coriolis effect is not strong enough to make them spin. The Coriolis effect is also why they move away from the equator Tropical cyclones are also known as hurricanes (when the occur in the Atlantic Ocean or Caribbean Sea) and typhoons (when they occur in the Pacific Ocean). Read P 7 Pearson
Aftermath of Isabel
Tropical storm hazards Heavy rain causes damage as it leads to floods and mudslides. High wind velocity can destroy structures And low central pressure can lead to storm surges and coastal flooding. Devastation can occur eg Hurricane Katrina
Read p 7 Pearson and p18 Philip Allan Could global warming lead to an increase in the strength of tropical cyclones because of increasing sea temperatures?
Exam practice P 25 Pearson Answer both Q a and b
Longer Exam Question HINTS Make sure you have a clear structure – write an introduction, then describe where they occur, followed by a section explaining why volcanoes occur there In the introduction, define Volcano, e.g. A volcano is a point where magma has risen from below the Earths surface and been ejected above ground. Next describe the global distribution of volcanoes, e.g. Volcanoes can be found all along the mid-Atlantic Ridge. They are also found around the edges of the Pacific Ocean (Ring of fire), particularly around Japan and Indonesia, and along the west coast of America (San Andreas Fault). They are also found in the centre of the Pacific Ocean in Hawaii. Now explain why volcanoes happen at each of the locations you have described. Make sure you use appropriate language, e.g. The mid-Atlantic Ridge is a constructive boundary. Here the mantle is under pressure from the overlying plates, and when they move apart pressure is released and the mantle melts, forming magma. This is less dense than the plates so it rises and can erupt to form a volcano. Describe and explain the global distribution of volcanoes (10 marks)