9. Hazardous Environments.pdf

CIE Geography A-level 9: Hazardous Environments Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0...

CIE Geography A-level 9: Hazardous Environments Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0 https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Tectonic Hazards Global Distribution of Tectonic Hazards Tectonic hazards are hazards caused by the movement of tectonic plates. These hazards usually occur on plate boundaries, which is where two tectonic plates meet each other. The global pattern of tectonic hazards are very clear on tectonic plate maps. (Source:www.geologyin.com) Global Distribution of Volcanoes and Earthquakes (Source: www.pbs.org/wgbh/nova/teachers/activities/2515_vesuvius.html) It can be seen that, on average, volcanoes and earthquakes occur on plate boundaries. Volcanoes occur on convergent boundaries (aside from when two continental plates move towards each other) and divergent boundaries. Earthquakes occur on all types of boundaries (divergent, convergent, or conservative). https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Plates do not perfectly fit into each other, meaning they do not move in fluid motions. At all boundaries, plates can become stuck due to the friction between plates. You can try this by moving one palm of your hand against the other, and it is clear that at some points there is more friction between irregularities and bumps, causing the hands to become stuck slightly. When the plates are stuck, the convection currents in the asthenosphere continue to push, which builds the pressure. It builds so much that it cannot be sustained and the plates eventually give way. All of this pressure is released in a sudden movement, causing a jolting motion in the plates This jolt is responsible for seismic movement spreading throughout the ground in the form of seismic waves (or shock waves). The focus is the point underground where the earthquake originates from. The epicentre is the area above ground that is directly above the focus. Magnitude Seismicity is measures using the logarithmic Richter Scale which is a measure of the strength of seismic waves. The Modified Mercalli Intensity Scale is also used, which is a rate of the destruction caused (originally the Mercalli scale when developed in 1884, but the name was changed after 1931 when it was modified). Unlike the Richter scale, https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  the Mercalli scale has a definite end at 12 (XII as it is in roman numerals). The Mercalli scale is subjective, meaning sometimes it is disputed as it is dependent on human development being present rather than the strength of the seismic waves. (Source: https://missnickles.wordpress.com/earth-science/) The magnitude of the earthquake is also dependent on the depth of focus. Conservative boundaries have the shallowest boundaries, meaning they are closer to the epicentre and the seismic waves are stronger. convergent boundaries usually have deeper focuses, meaning the seismic waves are spread over a larger area before they reach the epicentre. This is dependent on the earthquake. Frequency Earthquakes are frequent around the world and occur every day at boundaries. Hundreds of smaller magnitude earthquakes that cannot be felt by humans occur every day, whereas the larger earthquakes are less frequent. Regularity Earthquakes follow no pattern and are random so there is irregularity between events. Predictability Earthquakes are almost impossible to predict. Microquakes may give some indication but the magnitude cannot be predicted as how strong they are is random. Hazards caused by earthquakes: Shockwaves (seismic waves) - When two plates move side by side, friction builds up and pressure increases; this pressure is stored as potential energy, it cannot move so it just builds up. When the pressure becomes too much, the plates eventually move. All of the energy that has been built up must go somewhere, so it is transferred into kinetic energy, which is released and vibrates throughout the ground. The further away from the focus, the weaker the shockwaves, as the energy is transferred into the surroundings. This shaking alone causes many hazards, such as buildings and infrastructure collapsing. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Tsunamis When an oceanic crust is jolted during an earthquake, all of the water above this plate is displaced. The water travels fast but with a low amplitude (height). As it gets closer to the coast, the water becomes shallower, forcing the waves to become compressed into a smaller area. This causes the waves to slow down and gain height, creating a wall of water that is on average 10 feet high, but can reach 100 feet. Liquefaction - When soil is saturated, the vibrations of an earthquake cause it to act like a liquid. Soil becomes weaker and more likely to subside when it has large weight on it. Image: Liquefaction in Christchurch, New Zealand. Source:Stuff.co.nz Landslides and avalanches - Movement in soil or snow will cause it to become unstable. This can cause huge areas to give way, sending large amounts of debris or snow to tumble downhill. This can damage infrastructure and buildings, damage the environment, and poses a huge threat to life. (Source: blogs.agu.org/landslideblog) https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  TYPE OF SEISMIC HAZARD EFFECT Environmental Economic Social Political Primary - Earthquake can - Businesses - Buildings - Government cause fault lines destroyed collapse, buildings which destroy the - Immediate killing/injuring destroyed environment payout for people and - Liquefaction response trapping them - Homes destroyed Secondary - Radioactive - Economic - Gas pipes - Political unrest materials and decline as rupture, starting from food other dangerous businesses are fires which can kill shortages or substances destroyed (tax - Water supplies are water shortages leaked from breaks etc.) contaminated as - Borrowing power plants - High cost of pipes burst, money for - Saltwater from rebuilding and spreading disease international aid tsunamis flood insurance and causing floods - Can be initial freshwater payout - Tsunamis which chaos and ecosystems - Sources of lead to damaging ‘lawlessness’ - Soil salinisation income lost flooding e.g. looting https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Volcanoes occur on plate boundaries where plates melt and lava erupts through a plate. Alternatively, they may occur on hotspots too. Volcanoes on convergent plate boundaries Volcanic eruptions on convergent plate boundaries are usually explosive due to the high pressure the magma is under. Composite volcanoes, made from ash and lava, are formed from these eruptions. These volcanoes form in different ways dependent on the type of plate boundary: Continental and Oceanic Denser oceanic plate subducts below the continental. The plate subducting leaves a deep ocean trench. Fold mountains occur when sediment is pushed upwards during subduction. The oceanic crust is melted as it subducts into the asthenosphere. The extra magma created causes pressure to build up. Pressurised magma forces through weak areas in the continental plate. Explosive, high pressure volcanoes erupt through the continental plate, known as composite volcanoes. Oceanic and Oceanic: Heavier plate subducts leaving an ocean trench. Fold mountains will also occur. Built up pressure causes underwater volcanoes bursting through oceanic plate. Lava cools and creates new land called island arcs. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Volcanoes on divergent plate boundaries Volcanic eruptions on divergent plate boundaries are usually effusive as the magma is under less pressure, so the lava flows more freely. Shield volcanoes, made from mainly lava, are formed from these eruptions. These volcanoes form in different ways dependent on the type of plate boundary: Oceanic and oceanic: Magma rises in between the gap left by the two plates separating, forming new land when it cools. Less explosive underwater volcanoes formed as magma rises. New land forming on the ocean floor by lava filling the gaps is known as sea floor spreading (as the floor spreads and gets wider). Continental to continental: Any land in the middle of the separation is forced apart, causing a rift valley. Volcanoes form where the magma rises. Eventually the gap will most likely fill with water and separate completely from the main island. The lifted areas of rocks are known as horsts whereas the valley itself is known as a graben. Volcanoes on Hotspots Hotspots are areas of volcanic activity that are not related to plate boundaries. Hot magma plumes from the mantle rise and burn through weaker parts of the crust. This can create volcanoes and islands. The plume stays in the same place but the plates continue to move, which sometimes causes a chain of islands (such as Hawaii). Hazards caused by volcanoes: Lava flows - lava can flow quickly or slowly depending on its viscosity. Silica makes lava viscous and slow, which is common in explosive eruptions. Lahars - caused by a number of reasons, usually by melting ice at high latitudes Image: Lahar in the Tambour River, Guatemala. Courtesy of @ConredGuatemala / twitter https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Mudflows - different to lahars, which are volcanic material, mudflows may be triggered by the violent shaking that an eruption brings, or meltwater from the volcanic heat. Glacial floods (jökulhlaups) - when temperatures are high from lava, glaciers or ice sheets at high temperatures quickly melt and a large amount of water is discharged Tephra - any type of rock that is ejected by a volcano Toxic gases - released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier Acid rain - caused when gases such as sulfur dioxide are released into the atmosphere Volcanic landslides - High velocity flows of debris caused when the energy from the eruption blows apart rocks and other material, sending it down the volcanic slope Nuées ardentes/pyroclastic flows - clouds of burning hot ash and gas that collapses down a volcano at high speeds. Average speeds of around 60 mph but can reach 430 mph. Magnitude Vulcanicity is measured using the Volcanic Explosivity Index(VEI). The more powerful, the more explosive. The scale is logarithmic from VEI 2 and onwards. Multiple features are considered when calculating the VEI, including how much tephra is erupted, how long it lasts, how high the tephra is ejected etc. Intense high magnitude eruptions are explosive whereas calmer, lower magnitude eruptions are effusive. (Source: https://volcanoes.usgs.gov/vsc/glossary/vei.html) Frequency Frequency of eruptions varies per volcano. Volcanoes are classed as either active, dormant or extinct. An estimated 50-60 volcanoes erupt each month, meaning volcanic eruptions are always frequent (and some volcanoes erupt constantly). Usually, a higher frequency eruption means the eruptions are effusive whereas low frequency means the eruptions are explosive. Regularity Volcanic eruptions are regular in that the eruptions on each type of boundary are similar (e.g. eruptions on convergent boundaries will regularly be explosive) Sometimes eruptions may be irregular and not fit patterns. Predictability Regularity of eruptions can help estimate when eruptions will take place (i.e. every 10 years). Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  TYPE OF VOLCANIC HAZARD EFFECT Environmental Economic Social Political - Ecosystems - Businesses and - People killed - Government damaged through industries - Homes buildings and Primary various volcanic destroyed or destroyed from other important hazards disrupted lava/pyroclastic areas destroyed or disrupted - Wildlife killed flows - Water acidified - Jobs lost - Fires can start - Conflicts by acid rain - Profit from which puts lives at concerning Secondary - Volcanic gases tourism industry risk government contribute to - Mudflows or response, food greenhouse floods shortages, effect (global - Trauma insurance etc. warming) - Homelessness Hazards can be responded to by preventing them directly, being prepared for the next hazard, mitigating the effects, or completely adapting your lifestyle to limit the hazard’s effects. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Mass Movement Hazards Mass movement is the large scale movement of materials on a hillslope, caused when the stress exerted exceeds the internal strength of the hillslope, causing instability. Mass movement on a slope will always be downhill due to the force of gravity. These movements can happen over a range of timescales, and also depend on the moisture in the hillslope material, which is shown in the diagram below: Causes Mass movement processes occur due to slope instability, causing the slope to give way. Slope instability is generally caused by either (or a combination of both): an increase in external stress on the slope, or a decrease in the internal strength of a slope. For example: The slope may become too saturated, causing the material to give way, e.g. mudslides. Weathering and erosion can weaken the internal strength until it can no longer bear the load on the slope, e.g. freeze-thaw processes can cause large rocks to fall off a slope (rockfalls). Seismic waves may cause mass movement processes, triggering rockslides, landslides, mudflows and other processes. Multiple human activities can add stress to a slope or remove its strength (e.g. deforestation can remove tree roots, which causes soil to be less cohesive and therefore at risk of mass movement). https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Predictability Mass movement processes can be predicted and monitored through different technologies. Precipitation levels can be measured through a rain gauge or precipitation radars, which can show the risk of a mass movement processes that are triggered by heavy rainfall. Soil moisture content can be measured through different technologies (such as a time-domain reflectometer). Changes in the surface of a slope can be detected using radar technology, and other systems such as an inclinometer, which measures the incline of a slope. Seismometers measure seismic waves going through the ground, which can indicate whether there is a risk of a mass movement process being triggered. Using past data, predetermined indicators, and other means, scientists can predict whether or not there is a possibility of a mass movement event through these technologies. TYPE OF MASS MOVEMENT HAZARD EFFECT Environmental Economic Social Political - Ecosystems - Businesses and - People killed or - Government damaged through industries injured buildings and Primary destroyed slope destroyed or - Homes other important - Wildlife killed disrupted destroyed areas destroyed - Damage to or disrupted - Roads blocked environment - Infrastructure destroyed - Debris and mud - Jobs lost - Power outages, - Conflicts or can block - Money needed gas leaks etc. disagreements Secondary waterways and to rebuild and caused by broken concerning cause other clean up infrastructure. government environmental - Investments - Blocked roads response issues into slope stability - Trauma - Homelessness https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Atmospheric Hazards Large Scale Tropical Disturbances A tropical storm is a low pressure, spinning storm with high winds and torrential rain. Hurricane Florence from the International Space Station https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc There are certain conditions for a tropical storm to form and develop: Temperature: Ocean temperatures Rotation: Tropical storms only form must be around 26 - 27°C and at least around the equator, but no less than 5° 60 metres deep. Warm water provides on either side. The Coriolis Effect is the storm with energy. the effect of the Earth’s rotation on weather events. The storm spins Air pressure: Must be in areas of because the Earth is spinning; but there unstable air pressure - usually where is no Coriolis Effect at the equator, areas of high pressure and low pressure hence why these storms will only form a meet ( convergence ) - so that warm air certain distance away from it. rises more readily and clouds can form (this air must also be humid for cloud A trigger: a pre-existing thunderstorm, a formation). Warm air rises because it is spot of very high sea surface less dense than cold air. temperature, an area of low pressure and many other factors can act as a trigger Wind shear: Winds must be present for for a storm to develop, which will only the swirling motion to form, but not too further develop when the other strong or the storm system will be conditions are present. ripped apart in the early stages. Formation 1. Warm, moist air rises, leaving an area of low pressure below. This causes warm air from surrounding areas of higher pressure to move into this low pressure area and rise too. Overall, warm air is constantly rising and accumulating in the atmosphere. 2. When the warm air rises, it cools, condensing into thunderstorm clouds. 3. The whole system is spinning due to the Coriolis effect. In the southern hemisphere, the storms spin clockwise; in the northern, anticlockwise. 4. The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds.Furthermore, the difference in pressure between the low pressure centre and the higher pressure surroundings causes air to be sucked in towards the centre, enhancing the high winds. At 39 mph the storm can be classed as a tropical storm. 5. The eye of the storm is in the centre. This is an area spanning around 30 miles wide that is of extremely low pressure (can be 15% lower pressure than areas outside of the storm). Cool, dry air (cool from the higher altitudes and the moisture has been transferred into the system) descends in the eye, causing the weather to be relatively calm and cloud free. The more intense the storm, the clearer the eye. 6. Surrounding the eye is the eyewall, the most intense and powerful area of the storm. Warm, moist air rapidly rises here, with extremely high winds and torrential rain. When winds reach 74 mph, it becomes a hurricane/cyclone/typhoon. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  A cross section of a tropical storm is thought to look something like this: 7. When the tropical storm reaches a coast, the low pressure and high winds will cause a large amount of sea water to be taken into the system and then released as a high wave called a storm surge. 8. When the storm reaches land, it no longer has a supply of energy (warm, moist air from the sea) and the eye eventually collapses. Heavy rain can persist for days. Spatial Distribution Magnitude Measured on the Saffir-Simpson Scale (A scale of 1-5) based on wind speed and thus power of the storm. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Frequency Tropical storms form in the Northern Hemisphere from June-November, and the Southern Hemisphere from November-April. The majority of tropical storms do not develop into strong storms and do not reach land. Tropical storms that are higher magnitude and reaching land are thought to be increasing in frequency. Regularity Tropical storms are irregular because although they occur in the same areas, their path does not follow a set route - the route taken is dependent on the storm and the climatic conditions. Predictability Tropical storms form away from land meaning satellite tracking of cloud formations and movement can be tracked and the general route can be predicted. These projected path of Hurricane Florence estimates to the hour when the hurricane will hit. The first picture tracks 5 days in advance, the second picture is the day after. Note how the tracking changes within 24 hours. The closer the hurricane gets, the easier it is to predict. Storm surges can also be predicted based on the pressure and intensity of the storm. From past storms and climatic trends, the probability of a storm hitting an area can also be predicted. Scientists have predicted how many years it will take for a tropical storm to hit certain areas. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Hazards caused by tropical storms: High winds - over 300km/h and therefore very strong. Hurricane winds are strong enough to blow a house down, and also blow heavy debris at high speeds, which can obviously cause damage and injure anyone who comes into contact. Flooding - coastal/river flooding from storm surges and heavy rain. River flooding also sends more floodwater to other places, which can cause areas outside of the tropical storm’s path to flood also. Landslides - due to soil becoming heavy when wet with high levels of rain Storm surges - Large rise in sea levels caused by low pressure and high winds, pushing water towards the coast TYPE OF STORM HAZARD EFFECT Environmental Economic Social Political Primary - Beaches eroded - Businesses - Drowning - Government -Sand displaced destroyed - Debris carried buildings - Coastal habitats - Agricultural land by high winds destroyed such as coral reefs damaged can injure or kill are destroyed - Buildings destroyed Secondary - River flooding/ salt - Rebuilding and - - Issues paying water contamination insurance payout Homelessness back international - Animals displaced - Sources of - Polluted aid from flooding e.g. income lost water supplies - Pressure for alligators - Economic decline spread disease government to do -Water sources from sources of - Food more about changing course income destroyed shortages from global warming from blockages damaged land https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Small Scale Atmospheric Disturbances A tornado is a violently rotating moving vortex of air. Tornadoes are found in many areas across the world, especially within the middle latitudes. Tornadoes occur most frequently in the USA, and these tornadoes are usually the most violent. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc When the sun heats the ground, the hot air rises and then condenses into clouds. There must be an environment where higher winds are stronger and faster than the winds lower down for the formation to continue. The stronger, faster wind may start to roll underneath the weaker wind, which creates a rolling horizontal cylinder of wind. As the powerful, hot updraughts of air continue to rise, they can cause the horizontal cylinder to be forced upwards into a rotating vertical column of air. At this point, the storm is known as a supercell. Cool, dry downdraughts of air pull the rotating air downwards, causing the spinning vortex to spin faster and become tighter. If the rotating vortex of air reaches the ground, it is then classed as a tornado. Although the majority of tornadoes are small and short, some can be extremely strong and violent. Winds can exceed 200mph, destroying the majority of things in its path until it eventually loses energy. This video from the Met Office provides an overview of the formation with helpful illustrations. Magnitude The Enhanced Fujita Scale is used in some countries to rate the intensity of a tornado based on the damage it causes. EF0 is the lowest rating, whereas EF5 is the highest rating. The EF scale contains 28 damage indicators, which are used to make a judgement on the level of damage. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc  Frequency Tornadoes occur most frequently in the USA; there are an average of 1200 tornadoes each year in the US, compared to 100 in Canada, and 300 in Europe. They are most frequent in spring, and rare in winter. Predictability Although predicting tornadoes is not 100% accurate, there are ways to monitor tornadoes and spot warning signs. Favourable conditions for a tornado to develop can be monitored, e.g. intense thunderstorms. Warning signs may be sighted, such as funnel clouds, or a rear flank downdraft (the movement of cold air downwards). Radars and weather systems can spot signs of a tornado forming, or if a tornado is already on the ground. A Doppler Radar detects a large rotating updraft (called a mesocyclone) in a supercell based on its shape. Hazards caused by tornadoes: High winds - over 200km/h and therefore very strong. Tornado winds are strong enough to blow a house down, pick up automobiles, and also blow heavy debris at high speeds, which can obviously cause damage and injure anyone who comes into contact. Precipitation - flooding due to extremely heavy rain. This can lead to other issues, such as landslides. Hail often develops in a supercell, which can grow to be large enough to smash windows and cause serious injury. Hail developed in supercells can be ¾ of an inch or larger in diameter. Pressure imbalance - there is a huge pressure imbalance between inside the tornado (very low pressure) and its surroundings. If a tornado is passing through a house, the difference in pressure inside the house compared to outside alone is enough to rip off a roof and much worse. TYPE OF TORNADO HAZARD EFFECT Environmental Economic Social Political Primary - Destruction of - Businesses - Debris carried - Government habitats from high destroyed by high winds buildings winds and rain - Agricultural can injure or kill destroyed - Wildlife killed or land damaged - Homes and injured other buildings destroyed Secondary - Flooding from heavy - Rebuilding and - Widespread - Issues paying rain insurance payout power failure back - Landslides or other - Sources of - Psychological international aid natural structural income lost trauma as a - Pressure on failures due to - Economic decline result government to tornado and its storm from sources of - Homelessness provide aid etc. - Animals displaced income destroyed - Risk of injury due to destroyed due to destroyed habitats house (e.g. electrical injury) https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Hazard Perception People have different viewpoints of how dangerous hazards are and what risk they pose. These perceptions are dependent on lifestyle factors which include economic and cultural elements. Note that these are the economic and cultural factors of individual people rather than an entire population’s views. Wealth - The financial situation of a person will affect how they perceive hazards. Wealthier people may perceive a hazard to be smaller as they are less vulnerable (e.g. they have the ability to evacuate with transport access, build stronger houses etc.). However, wealthier people may also view a risk as greater as there is more risk of property damage and financial loss than someone less wealthy. This is, of course, dependent on the person. Experience - Someone who has experienced more hazards may be more likely to understand the full effects of a hazard. There are also studies suggesting that people who have experienced hazards are likely to have an optimistic and unrealistic outlook on future hazards, almost like a ‘lightning never strikes the same place twice’ mentality. R. Kates describes this in his journal: Natural Hazard in Human Ecological Perspective: Hypotheses and Models, 1971. Education - A person who is more educated about hazards may understand their full effects on people and how devastating they can be and have been in the past. Those who are less educated may not understand the full extent of a hazard and may not evacuate etc. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Religion and beliefs - Some may view hazards as put there by God for a reason, or being part of the natural cycle of life etc. so may not perceive them to be negative. In contrast, those who believe strongly in environmental conservation may perceive hazards to be a huge risk to the natural environment, especially hazards that are becoming more frequent due to global warming. Mobility - Those who have limited access to escape a hazard may perceive hazards to be greater threats than they are. Whether they are in a secluded location, or if they are impaired with a disability or illness, those who cannot easily leave an area quickly may feel more at risk. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc