Revision of Unit A3 Hazards Part 1
The next 4 weeks: Hazards • Key idea 1: Some places are more hazardous than others. • Key idea 2: Hazards have an impact on people and the environment. • Key idea 3: Different levels of economic development affect how people cope with hazards.
Hazards Week 1: • Key idea 1: Some places are more hazardous than others • Essential content • Different types of hazard (climatic, tectonic, etc). • The global distributions, causes and characteristics of tropical revolving storms, volcanic and earthquake activity (plate movements). • Measuring and recording weather conditions, eg strong winds, intense rainfall. • Mapping the global distribution of recent hazards. • Collecting and recording weather data (fieldwork opportunity).
Hazards Week 2: • Key idea 2: Hazards have an impact on people and the environment. • Essential content • Identifying the scale of natural disasters and their short-term (deaths, injuries, damage to buildings and infrastructure) and long term (homelessness, costs of repairing damage) impacts. • Reasons why people continue to live in areas at risk from hazard events. • Research into a recent hazard event (egg satellite images, damage photographs). • A comparative study of the impacts of tropical storms, in an LIC and an HIC.
Hazards Week 3/4: • Key idea 3: Different levels of economic development affect how people cope with hazards. • Essential content • Managing hazards (tropical storms, volcanic eruptions and earthquakes) involves taking actions both before and after the event. • Predicting and preparing for hazards (education, early warning systems, shelters). • Responding to hazards: short-term (emergency aid and disaster relief); long-term (risk assessment, adjustment, improving prediction). • Surveying peoples’ views on the management of a hazard event • Case studies of the management of one tropical storm and one tectonic event. One of these should have happened in an LIC and the other in an HIC.
So this week Key Idea 1 Some places are more hazardous than others
Different types of hazard (climatic, tectonic, etc). • A natural hazard is a threat of a naturally occurring event that will have a negative effect on people or the environment. • Many natural hazards are interrelated, e.g. earthquakes can cause tsunamis and drought can lead directly to famine. • If this threat becomes a serious reality then it becomes a disaster. • If you live on the edge of a tectonic plate, then earthquakes are a hazard. • A natural hazard becomes a natural disaster when it affects people, officially causing more than 10 deaths, injuring more than 100 people, and/or causing US$16 million of damage. • So the San Francisco earthquake was a disaster because: • US$400 million ($9.5 billion in 2009 dollars). • Over 80% of the city was destroyed by the earthquake and fire • Over 3000 died from the earthquake and the fire that followed as a result of gas leaks etc • About 300,000 of the 410,000 population were made homeless • Injury figures have not been established
Different types of hazard (climatic, tectonic, etc). • Natural hazards include: • Avalanche • Landslide and mudflows • Volcanic eruptions • Lahar • Flood • Tsunami • Tropical storms • Tornados • Wildfire
The global distributions, causes and characteristics of tropical revolving storms • They are known under 3 names: • They are hurricanes of the United States and the Caribbean • They are tropical cyclones on the India Ocean • They are Typhoons in the Pacific • They have wind speeds of at least 120km/hr • They only usually occur within a band from 20 Deg North to 20 Deg South of the equator. • They do not happen at all times of the year but are most common between mid summer and autumn. • So for the Southern Hemisphere this is between December and April while in the Northern Hemisphere, it is between June and October.Those storms whose wind speed do not reach these higher limits but have wind speeds reaching 60 km/hr are usually called tropical storms.
The causes and characteristics of tropical revolving storms • They form over warm sea which has a temperature of at least 26 deg C • The warm sea evaporates and warms the air above it. • The warm moist air rises, causing low pressure. • As this warm air rises, it cools and the water vapour condenses into huge tall cumulous clouds • The trade winds swirl in and towards the low pressure to replace the rising air. • This air then become warm and moist and rises upwards. • The swirling air around the centre of the storm pulls the warm, damp, rising air outwards.
The causes and characteristics of tropical revolving storms • This makes the whole storm spin at increasing speed. • Thus the ‘eye of the storm’ is a low pressure centre down which cold, dense air from above air from above drops and adds to the warm moist spinning air that is rising up. • It continues to build in size and speed, getting all its energy from the warm water below. • The force of the spinning storm pushes down on the sea below it so that a wave forms a rim around the storm. • As the swirling storm picks up speed, it begins to move in a westerly direction away from the equator (so that is NW in the Northern Hemisphere).
The characteristics of tropical storms • If it approaches landfall, the wind will begin to pick up and the dark thunder clouds can be seen approaching. • On the coast, the first real sign might well be a tidal surge, a big wave up to 7 metres high, caused by the downward pressure of the storm on the sea, made higher in front, like the bow wave on a ship, as the storm moves forward. • The very high winds and torrential rain will follow. • At some point, the wind may drop and rain lessen, if the eye of the storm passes over. • But the wind and rain will soon pick up again. • However once the storm has blown onto the land it will soon loose speed and ferocity, as its source of energy, the warm water, is no longer there to feed the storm. If this is too wordy for you, go and look at the animation on http://ih-igcse-geography.wikispaces.com/3.2+Characteristics%2C+distribution+and+causes+of+tropical+storms
The global distributions, causes and characteristics volcanic and earthquake activity (plate movements). • The earth’s structure consists of: • A core • A mantle • A crust • The crust is broken into a number of pieces called plates. • The plates are moved by the viscous up-across-down, convection current movement of the mantle. • It is mostly due to these movements that earthquakes and volcanoes occur along the plate edges.
These are the 4 kinds of plate movements. I have deliberately grouped them in 2 pairs. How the pair on the left different from those on the right? On drawing subduction is taking place – which one and what does it mean? There are heavy dense oceanic plates and lighter continental plates. What kind of plates are in each of these plate movements? The global distributions and causes volcanic and earthquake activity
The global distributions and causes volcanic and earthquake activity Can you give me examples of where each type of plate is found?
The global distributions and causes volcanic and earthquake activity Can you see the link between the plate edge and the type of activity that takes place along it? Green = major plates – there are lots of small ones that do not show Yellow = earthquakes Red = Volcanoes
The causes and characteristics of earthquake activity • Earthquakes occur mainly on plate boundaries that are moving towards, past or away from each other • Over many years pressure builds up until eventually the rocks snap along a weak area called the FAULT LINE • The point of origin of an earthquake is the FOCUS – this is the point where it starts from • The place at the surface directly above the focus is called the EPICENTRE What sort of margin is this?
The stored energy is released, travelling outwards in SEISMIC WAVES Seismic Waves are strongest at the epicentre of an earthquake – this is where the most damage is caused Seismic Waves spread out from the focus like ripples *AS SEISMIC WAVES TRAVEL OUTWARDS THEY LOSE ENERGY* The closer to the surface the focus of the earthquake is and the softer the rocks, the higher the magnitude of the seismic waves and the greater the damage
The causes and characteristics of earthquake activity • The magnitude of an earthquake is measured on the Richter Scale • An earthquake’s magnitude (the strength) is measured using a seismograph. • Each subsequent level is x10 more powerful than the previous on was. • The scale is continuous (has no end) although nothing above 9.2 has not been recorded on land.
But the only problem with Richter is … • That it tells you about the strength of the earthquake at focus/epicentre and so each earthquake only has 1 value. • But obviously, this tells you nothing about what it is like further away – is there any damage? How great is the damage? • So there is another measure of earthquakes, which when you are looking them up you may come across. • It is called the Modified Mercalli Scale - it is often measured using Roman Numerals I, II, III, IV etc • Go to the animation where you can get an appreciation of what an earthquake may feel like as various points on the scale • http://newigcsenotes.wikispaces.com/3+Hazardous+environments
An example • On September 29 there was an earthquake under the sea, south of Samoa and American Samoa had a Richter scale of 8.0 (or 8.3 depends who you read) the Richter scale predicts serious damage across several hundred kilometres. • But the Mercalli scales for these were Samoa felt (V) and (IV) at American Samoa. • But it was the tsunami that did the damage. At least 149 people killed in Samoa, 34 people in American Samoa and nine people killed and four injured on Niuatoputapu, Tonga. Widespread damage to infrastructure at Pago Pago and Samoa.
The characteristics of earthquake activity • There are 2 types of waves in an earthquake • Body waves and surface waves. • Body waves travel outward in all directions, including downward, from the quake's focus -- that is, the particular spot where the fault first began to rupture. • Surface waves, by contrast, are confined to the upper few hundred miles of the crust. • They travel parallel to the surface, like ripples on the surface of a pond out from the focus. They are also slower than body waves.
The characteristics of earthquake activity • Following an earthquake … • ..the body waves (P-wave) strike first and are the fastest kind People often report a sound like a train just before they feel a quake, which is the P-wave moving as an acoustic wave in the air. • Then the secondary, or S-waves, arrive. A person in a building perceives the arrival of S-waves as a sudden powerful jolt, as if a giant has pounded his fist down on the roof. • Finally, the surface waves strike. In very strong earthquakes, the up-and-down and back-and-forth motions caused by surface waves can make the ground appear to roll like the surface of the ocean, and can literally topple buildings over.
1.The continental crust is folded and faulted by the pressure of the subduction 2. The trapped magma escapes through the fault to form a volcano 1.The oceanic crust subducts under the continental crust 2. It warms up and turns into magma that is trapped under the crust above it The causes of volcanic activity This is one worth learning to draw
Just to remind you – here are the plates and … Where are the places the volcanoes occur most commonly? Why is that?
The characteristics of volcanic activity • Often earthquakes occurring near a volcano can be one of the first warnings of things to come • Lava: it can be thick, viscous (sticky) lava or much more runny. • The thick lava moves relatively slowly and hardens quickly to form new rock – and so forms a cone shape a cone shape. Eruptions tend to be violent. • Eruptions that give out the thin, runny lava tend to be frequent but relatively gentle and come from a shield volcano. • Pyroclastic flow: some volcanoes do not give out lava alone but a mixture of hot steam, ash, rock and dust. • A pyroclastic flow can roll down the sides of a volcano at very high speeds and with temperatures of over 400° C.
The characteristics of volcanic activity • Ash clouds may affect more than the immediate area. They consist of water vapour, sulphur gas as well as small rock fragments and tiny pieces of glass. • Many of these will return to earth and add a layer of dust to a wide area. • However, the gases may be carried a long way by the wind once they have reached high enough into the atmosphere. This may be carried all around the world ad has in the past had a lasting impact on the climate, lowering the temperature for a year or more. E.g. Krakatoa in 1883 is the largest volcano eruption in recorded history for which we have data. • Average global temperatures fell by as much as 1.2 degrees Celsius in the year following the eruption. Weather patterns continued to be chaotic for years and temperatures did not return to normal until 1888.
Finally Lehars • These can occur at the same time as a volcanic eruption but may also occur over succeeding years. • Lahars form when water from intense rainfall, melting snow and ice, or the sudden failure of a natural dam, mixes with loose volcanic material, creating mudflows that can be particularly dangerous and destructive. • Although lahars contain a lot of volcanic ash and rock fragments–making them dense and viscous like wet concrete–they actually flow faster than clear-water streams. • These mudflows can rush down the flanks of a volcano at speeds as great as 65 kilometres per hour and can travel more than 80 kilometres. Lahars that contain the most debris move the fastest and are the most destructive.
VEI = Volcanic Explosivity Index • This measure the size of the eruption after it is finished. • However, forecasting an eruption on a scale is rather more complicated, as each volcano has a slightly different way of behaving so there are almost as many scales as there are volcanoes! But most use a variation on the green (no problem), yellow (not much to worry about), orange (watch this space!) and finally red (move NOW) warning system.
Collecting and recording weather data • Many of you had a go at a variation on this. But there is an indication that the way this could be examined is by them asking you how you collect weather data. • Whilst most data is collected electronically these days, you are still expected to understand the ideas behind how these measurements are made, so you need to know how the basic instruments work even though you will probably never use many of them!
What you need to measure: Temperature including maximum and minimum Pressure Wind speed and direction Precipitation What pieces of kit you need to understand: Thermometers various Stevenson’s screen Barometer Anemometer Weather Vane Rain gauge Collecting and recording weather data
The thermometer Usually consists of a hollow glass bulb attached to a narrow stem with a thread-like bore. The bulb is filled with either mercury or alcohol stained red. The liquid in the tube expands when the temperature rises and contracts when the temperature falls. The amount of expansion and contraction is measured by a numbered scale. Whilst thermometers are really measuring their own liquid temperature, they are used to measure the temperature of the surrounding air. To make sure that the temperature of the surrounding air is the same as the thermometer, it must be shaded from sunlight and be exposed to adequate ventilation. These conditions are provided by a Stevenson screen. Collecting and recording weather data Why is it white? Why are there louvers? Why is it on legs? Why the large roof? Met office Stevenson screens in the UK have doors facing north. Why?
Wet and dry thermometer If the air is dry, any water will evaporate quickly. As water evaporates is removes heat from its surroundings to give the energy to change from a liquid to a gas. One of these thermometers has a supply of moisture wrapped around its bowl, so on a dry day, this will evaporate and reduce the wet thermometer’s temperature. The difference in the temperature between the 2 thermometers can be used to calculate the % of moisture in the air. Collecting and recording weather data
Air Pressure • One instrument used to measure air pressure is called a barometer. • But a more usual one used in weather stations is a barograph. • The motor rotates the drum containing the paper chart. • The capsules are flexible metal discs from which nearly all the air has been extracted. As the external air pressure increases, the discs squash together more, and this rotates the arm so that the end with the pen on draws an upward line on the drum.
Wind speed is measured using an anemometer. An anemometer is made up of cups attached to handle with a scale on it. The stronger the wind the faster the cups rotate and the higher the reading on the scale. A wind vane is used to measure wind direction. It is measured using compass directions (north, south, east or west) from which the wind has blown so in this case the wind is coming from the ENE Collecting and recording weather data
Collecting and recording weather data • The instrument used to measure rainfall is a rain gauge. • Notice that the precipitation runs into a funnel and from there into a bottle. • The bottle will be calibrated to measure the depth of rain falling on a 127mm circle. Notice that the storage bottle is below ground. Why might that be? Why do you think the distance above ground of the gauge top is also fixed?
Key idea 2: Hazards have an impact on people and the environment. • Essential content • Identifying the scale of natural disasters and their short-term (deaths, injuries, damage to buildings and infrastructure) and long term (homelessness, costs of repairing damage) impacts. • Reasons why people continue to live in areas at risk from hazard events. • Research into a recent hazard event (e.g. satellite images, damage photographs). • A comparative study of the impacts of tropical storms, in an LIC and an HIC.
Short term impacts of natural disasters Avalanche Landslide and mudflows Wild fire Lahar Volcanic eruptions Tropical storm Flood Tsunami Tornado Do they high or medium or low mortality associated with them? Are there a few or lots of injuries Are these local or national or international? Are many home damaged Is transport hit? Is a lot of farmland/crops destroyed Is a lot of farmland/crops destroyed Are the services damaged – water electricity etc Can anyone think of any others?
Long term impacts of natural disasters Avalanche Landslide and mudflows Wild fire Lahar Volcanic eruptions Tropical storm Flood Tsunami Tornado Will it take a long time to repair roads railways and airports Will it cost a lot to put right? Will there be many long term homeless? Will there be enough food being produced or will long term aid be needed Are many home damaged Is transport hit? Will the services be able to be reinstated? Can anyone think of any others? Will the businesses be able to restart?
Reasons why people continue to live in areas at risk from hazard events. • A natural event (e.g. earthquake, flood, landslide, volcanic eruption, tropical storm) that has the potential to cause damage, destruction and death present as a natural hazard. So Hazard is the potential to cause harm. • Risk on the other hand is the likelihood of harm (in defined circumstances, and usually qualified by some statement of the severity of the harm). • How frequently is there a risk? How serious can it be? Is there anything that can be done to reduce the risk? • This is a risk assessment.
Reasons why people continue to live in areas at risk from hazard events. • People make decisions on the basis of: • Physical/ environmental – how often will I be at risk? The climate is good (warm enough and wet enough), soil is fertile, the natural resources for fishing, farming are there to make a good living • Human/social – the family has always lived there, there is a community, work, it is a pleasant place to be, do not have a choice or do not see themselves as having one, lack of education to do other work. There are things that can be done to reduce the risk (but more about that in the next week or 2) • Economic – work, from farming, tourism maybe, fishing, it is where property is owned.
Reasons why people continue to live in areas at risk from hazard events. Can anyone think of any other ideas? • In particular near volcanoes: • The soil is excellent. Lava breaks down over time to produce the most fertile soil on earth. e.g. around Vesuvius where much of Italy’s tomato crop is grown. • Along plate edges, geothermal power is often a cheap and clean source of power – e.g. Iceland • Usually, there are sufficient signs to move to safer places, so while property could be as risk, increasing people are less so, e.g. Mount Pinatubo in the Philippines in 1991 was the 2nd largest eruption in the 20th century but only 300 died because of mass evacuation of the area. • Tourism is a strong pull, e.g. in Uganda, a country trying hard to increase its tourist industry, the volcanic region around Mt Elgon is being heavily promoted for it's landscape, huge waterfalls, wildlife, climbing and hiking and its remote 'get away from it all' location.
Reasons why people continue to live in areas at risk from hazard events. • In particular in earthquake zones: • Along plate edges, geothermal power is often a cheap and clean source of power – e.g. Iceland • Many earthquake areas are close to the coast – the climate is good, fishing and farming are easy. • Many of these places like Japan get daily earthquakes and they have learnt to deal with them. They causes little or no damage as they adjust building methods for example. • The big ones are very infrequent – 1906 and 1989 in San Francisco, so people believe they can manage. Can anyone think of any other ideas?
Reasons why people continue to live in areas at risk from hazard events. • In particular areas subject to cyclonic storms: • These are close to the coast – the climate is good, fishing and farming are easy. • Transport links tend to be good and the flat land near the coast is a good place to build towns and cities. • With modern technology, there should be enough time to evacuate areas in danger (although as with Katrina the right choices are not always made), so while danger to property and services are still at risk, the danger to life should be much reduced. Can anyone think of any other ideas?
Research into a recent hazard event (e.g. satellite images, damage photographs). • Those of you who were here last autumn had several chances to investigate current recent hazardous events. • Those of you who were not might like to look at the Haiti earthquake – there is some good stuff on the wiki which you could use as a starter, but do try find some more yourselves. – see list of links under the PP in the wiki • http://newigcsenotes.wikispaces.com/3+Hazardous+environments