- Created by: Emma
- Created on: 22-04-12 12:46
A disaster hotspot is a country which is affected by two or more hazards with a vulnerable population. They are extremely disaster prone for a number of reasons.
- Hotspots are likely to be where plate boundaries intersect with major stormm belts in areas of high human concentration in low or medium developed countries.
- 790 million people are highly exposed to two or more hazards and 105 million exposed to areas with three or more hazards.
- The six countries prone to the most hazards are the Philippines, japan, India, Bangladesh, china and Indonesia.
Contrast between Philippines and California
Status RIC MEDC
GDP per capita $5,000 $40,000
HDI 0.75 0.95
Pop growth rate 2.3% 0.7%
Infant mort (per 1000) 40 7
Landscape Mountainous, 7000 small islands Coastal area
Contrast between Philippines and California summar
A classic hotspot where typhoon belt interacts with a plate boundary in a rapidly developing country. El Nino and La Nina cycles increase the range of hazards.
- Earthquakes, volcanoes, landslides, typhoons, flooding, tsunamis, drought
An area ranging from subtropical to tropical. It is a major tectonic hotspot also subject to extreme weather hazards brought on by El Nino and La nina.
- Earthquakes, tsunamis, flash floods and fire
Why is the Philippines a hazard hot spot? (Physica
- It sits on a major plate boundary therefore is at risk from earthquakes and volcanoes
- Its northern and eastern coasts face the pacific which is the worlds most tsunami prone ocean.
- It lies within South-East Asia's major typhoon belts.
- Landslides are common in mountainous areas.
- The philippines is densely populates
- It is a rapidly developing country (RIC)
- Their vulnerability is increased by; poverty, deforestation, poor land management and rapid urbanization.
What are the main hazards? (Philippines)
- Typhoons are the main hazard (20% a year)
- Volcanic eruptions are explosive with dangerous lahars, intermediate volcanic activity and composite cones.
- Earthquakes are common with 100% of the country at risk
- They have occasional droughts associated with El Nino
- Landslides are common in mountainous areas.
Hazard events in rank order - Top is most frequent
Typhoon - caused by temperatures above 26.5, low pressure and water deeper than 70m.
Flood - caused by low pressure, heavy rainfall, ITCZ
Landslide - caused by flooding, high rainfall, deforestation, urbanisation and earthquakes.
Earthquake - caused by plate boundaries and movement along plates.
Volcano - Destructive and conservative plate boundary, partial melting and intermediate magma.
Drought - caused by the ITCZ not migrating, lack of prevaling wind, poor rate of precipitation, high pressure in El Nino year.
Tsunami - caused by earthquakes, volcanoes and landslides.
Tectonic Hazards - Philippines
- It lies on the boundary between the Philippines and Eurasian plate. The Philippine plate is forced beneath the eurasian plate. They move in a series of jerks producing an earthquake each time. This is a destructive plate boundary.
- The most destructive volcanoes occur on these plate boundaries. As the magma melts in the mantle the magma forms in a magma chamber. Some becomes explosive especially where it combines with gases. The magma cools and solidifies below the earths surface and pressure builds and eventually releases.
- 80% of the worlds volcanoes occur along destructive plate boundaries.
Mnt Pinatubo - June 1991
- The biggest the world had seen for over 50 years
- 10km exclusion zone set up eventually extended to 30km
- By 9th June 58,000 people had been evacuated reaching 200,000 by 12th
- The eruption cause pyroclastic flows and huge lahars.
- 350 people died, including 77 in the lahars
- 80,000 hectares on land buried beneath ash disrupting 500,000 farmers.
- Economic losses of $710 million
Guinsaugon Landslide - February 2006
- Guinsaugon is a village in central Philippines on Luzon island
- In Feb 2006 a mud slide completely engulfed the village and its land, covering 3km(squared)
- It killed about 1150 people
- The physical causes could be torrential rain, la nina (rainfall) or a 2.6 magnitude earthquake
- The human causes included deforestation and replacing native forests by shallow rooted trees i.e coconuts.
- Earthquakes are the main risk. Large shallow earthquakes occur along the faults associated with the San Andreas fault. Conservative plate boundary.
- Floods occur in El Nino years and droughts and wildfires in La Nina years.
- Fogs occur due to high pressure which causes a build up of moisture.
- Landslides are frequently caused due to floods and earthquakes.
- Coping capacity is high
- Economic costs are high especially if a disaster strikes a megacity.
Loma Prieta earthquake in San Francisco
- Magnitude 7.1 and aftershocks of around 5.2
- 63 people died (most killed by freeway collapsing) and 13,757 were injured
- 366 businesses were destroyed and 3530 damaged
- Damage cost $6 billion
Northridge Earthquake - Los Angeles 1994
- Magnitude of 6.7 striking densely populated areas.
- Many thousands of after shocks of magnitude 4/5
- 57 people died and over 1,500 were seriously injured.
- 12,500 buildings were damaged and 25% suffered severe to moderate damage
- 9000 homes and businesses were without electricity for several days
- There was damage to several freeways
Coping with earthquake threats
Most Californians insure their property but because of the earthquakes demand increased. Many people stopped getting insured because they say that no earthquake occured between 1906 and 1989 so why bother.
El Nino and La Nina
El Nino - California (Philippines is the opposite)
- Sub tropical storms bring heavy rain
- On-shore moist winds
- Increased landslides
La Nina - California (Philippines is the opposite)
- Dry warm air with little rain
- increased drought risk
- increased risk on bushfires
The Philippines - Generalised
Hazards - Volcanic eruptions, shallow landslides on steep slopes, around 20 typhoons a year, earthquakes, tsunamis, risk from floods and El Nino can bring drought.
Coping capacity - cyclones cost the country around 5% of the total GDP, scattered islands are difficult to access and bring relief to, good relationship with the USA and it has a high quality research centre.
Vulnerability - High because of poverty and human development, increasing urbanization can add to earthquake and typhoon vulnerability, slopes, deforestation and flash flooding during typhoons.
California - Generalised
Hazards - earthquakes, coastline is vulnerable to tsunamis, floods and fires.
Vulnerability - 6% of the pop live on a floodplain, millions live on active faults. The high canyons and ridges which are common areas for wildfires are popular places for the rich and famous to live.
Capacity - Coping capacity is high, the state tends to lead relief efforts, they are used to reacting to there events so react well. The USGS advises on earthquakes and provides detailed information on ground shaking risk. building codes are strictly enforced, widespread education, they have one household emergency kits and warning systems for floods and tsunamis.
RISK= Hazards x Vulnerability
capacity to cope
Destructive Plate Margins
- Oceanic Crust - Oceanic Crust E.g New Zealand
- Oceanic Crust - Continental E.g Andes
- Many shallow, intermediate and deep focus earthquakes
- intermediate(sometimes acidic) volcanism
- Explosive volcanism (pyroclastics)
- Composite cones
Destructive Plate Margin
- Continental - Continental
- E.g Himalayas
- No subduction therefore no volcanism
- Lots of shallow focus earthquakes
- No subduction
- e.g situan earthquake
Constructive Plate Margins
- Lots of low magintude shallow focus earthquakes
- Lots of basic volcanism - basalt
- Low viscosity kavas
- Fissure eruptions
- Shield volcanoes
- e.g Iceland
Conservative Plate Boundary
- No loss or gain of crust
- Lots of low-high magnitude shallow focus earthquakes
- No volcanism
- No subduction therefore no melting of plates
Types of Volcano
- Usually formed at constructive plate boundaries
- Low with gentle sloping sides
- Formed by eruptions of thin, runy lava
- Frequent but gentle
- e.g Hawaii, Mouna Loa and Mauna Kilauea
- Formed at destructive plate boundaries
- Oceanic-Continental subduction
- It partially melts creating a magma dome
- e.g Mount Fuji, philippines and mount pinatubu
Types of Volcano 2
- Formed from giant cracks that open in the ground and expel fluid lava.
- Occurs along a fault produced by tensional stress
- Line of eruptions
- e.g Mount Tarawera, Hawaii and Iceland
- Forms when lava blocks the vent
- Lava cools then breaks
- New lava covers the cool lava
- Viscous acidic magma
- e.g Mount St Helens and West Indies.
- Localised areas of the lithosphere with an unusually high heat flow
- Caused by a mantle plume
- Below an oceanic plate = Basic magma basalt
- Shield volcanoes (Low viscocity basic magma)
- Effusive eruptions
- Island Chains
- Below a continental plate = acidic magma
- Explosive volcanicity
- lava domes
- e.g Yellowstone hotspot
- Some low-magintude earthquakes occur as a prelude to an eruption as magma is moving into the magma chamber.
Lava Flow - Hot liquid lava flowing e.g Kilauea
Lahars - A mixture of hot ash and water that forms a boiling mud flow e.g mount pinatubu
Pyroclastic flows - Fast flowing current of liquid ash e.g mount pinatubu
Tsunamis - A tidal wave from displaced sea (earthquakes, landslides and volcanoes) e.g Japan (earthquake sendai, volcano crackatoa)
Landslides - Downward sliding of earths crust e.g mount st helens
Fires - Caused by eruptions e.g Australia
- 7th biggest killer
- 1,400 deaths a year
- Human factors - deforestation (roots kept land together) and urbanisation (more erosion due to more run off which causes flooding)
- Physical - steep slopes, high rainfall (e.g ITCZ low pressure), hurricanes and monsoons (adds heavy rain to saturated soil), earthquakes and volcanic eruptions.
- An area of low pressure due to intense solar radiation found when the sun is highest overhead. As it migrates it brings convectional heavy rain. If it stays too long floods occur. If it fails to reach an area we get drought.
High and Low Pressure
- No clouds
- The air warms and becomes drier
- Caused by descendign air
- Causes drought, less wind, hot summers and cold icy winters.
- Caused by air heating, expanding and rising
- Clouds and rain
- More moisture
- Tropical cyclone/hurricane
Hurricanes + Storm surges
- In regions where there are warm temps above 26.5 degrees
- Intense low pressure
- Dont form over land
- Need water at least 70m deep
- Lose energy on land
- Need a spin
- Generally between the tropics
- Low pressure
- High winds
- Waves have a long fetch
- High Tides
- Funnel shaped coasts
Tornadoes + Drought + Wildfires
- Tornadoes generate when cold air meets warm air.
- Most frequent in May
- They need a spin
- They may generate if the ITCZ doesnt migrate
- El Nino and La nina
- Perminant Drough - Desert and high pressure
- Associated with drought in wildfires
- When the temps are high the forests dry out and may catch fire.
Dust storms + Snow/Ice
- They are formed when loose layers of dust and sand are blown away
- As you get further away from the equater the snow cover increases. The equator is called temperate, then boreal, tundra then finally the arctic which is snow and ice
- Areas further away from the poles have more snow
- Also areas with high relief accumulate snow as temps decrease with height e.g mt kilimanjuro is found at the equator but has snow and ice fields as its so high.
Londons Flood Risk
- The worst affected areas are close to the Thames
- Prolonged rainfall
- Sudden storms
- Storm surges
- Low air pressure
- Reduced by thames flood barrier