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Unit III – Chapter 4. Natural hazards and Disasters. Floods Earthquakes Hurricanes Tornadoes Volcanoes Tsunamis Avalanches. What are they?. Aspects of physical world that have potential to cause considerable harm to people a dormant volcano. What is a Natural hazard? .

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what are they








What are they?
why are natural disasters taking a heavier toll these days

Occur most often in heavily populated areas in southern hemisphere

Poorer countries with less solid infrastructure

More difficult for poorer countries (LCD and LLCD) to react quickly and compensate for loss

Why are Natural Disasters taking a heavier toll these days?
factors used to c0mpare natural disasters


  • How often a particular event is likely to occur
  • Duration
  • How long an event will last
  • Extent
  • How large an area or region will it effect
  • widespread or restricted to a small area
Factors used to C0mpare natural disasters

Speed of onset

  • How much warning will you get
  • Spatial dispersion
  • Area affected by disaster – prediction of where it will take place
  • Temporal spacing
  • How hazards occur in time – hurricanes occur in the same areas at the same time of year; while volcanoes are unpredictable
classifying natural disasters

Loss of life

Number of injuries

Damage to property

Intensity/strength of event

wind speed, Richter scale for earthquakes

Event causes other hazards – atmospheric, biologic and geologic

Classifying natural disasters
what is a global hazard

An event that affects people in many areas of the world

An event that has long term effects (for many years)

An event that causes permanent damage or serious contamination of the natural environment

What is a global hazard?
types of atmosphere hazards disasters

Severe storm

Cyclonic storm – hurricane, cyclone, typhoon





Types of Atmosphere hazards/disasters
cyclonic storms

Connected with weather and climate changes

normal weather patterns develop because of differences in air masses

Prevailing winds shift these air masses

When two air masses collide a sharp boundary called a front forms

Rotating low pressure areas, or cells form along storm front

Depending on how different the air masses are influences the types of storm that will develop

Cyclonic storms
tropical cyclones

Develop as the result of high temperatures and large amounts of water vapour

Develop over oceans and follow curved storm paths

Moved by prevailing winds and the Coriolis effect

Usually hit land where they cause significant destruction

Tropical cyclones
hurricane vs tornado
Hurricane vs tornado
  • Form over water
  • Called hurricanes - Atlantic; cyclones – Indian; typhoons – Pacific
  • Most destructive of all natural disasters
  • Follow curved storm paths and often end up over land
  • Cover extensive areas
  • High winds, rain
  • Extensive area so more widespread damage
  • Form over land
  • Called twisters, funnel clouds
  • Occur mostly in middle latitudes with thunderstorms that are part of cyclonic storm forming on cold front
  • Narrow path
  • High winds, rain
  • Limited area so less widespread damage
floods and flooding

High precipitation associated with a storm front

Rivers rise, overflow and flood adjoining lowland

Storms can cause “storm surge” which cause extensive lowland flooding

Storms can also cause mudslides

Floods and Flooding

Extended periods without rainfall

Prolonged drought – crop failure, death

i.e. Sahel area of sub-Saharan region of Africa

Desertification = productive dry land is degraded to the point where it is no longer productive

biologic natural hazards and disasters
Biologic natural hazards and disasters

Millions of deaths attributed to infectious or parasitic diseases


Prior to 2000 – 1.2 million children died/year (textbook)

In 2008 - 164 000 measles deaths globally – nearly 450 deaths/day or 18 deaths/hour

Measles vaccination (up 72% from 2000) resulted in a 78% drop in measles deaths between 2000 and 2008 worldwide

LDCs and LLDCs – 95% of deaths


By the end of 2008 - 33.4 million people worldwide were living with HIV

2 million people died of AIDS-related illnesses.

Globally, less than 1 in 5 at risk of HIV has access to basic HIV prevention services.

Only 36% of people who needed HIV treatment had access to it by end of 2009

2010 report – significant progress is being made


HIV/AIDS progress report from 144 low- and middle-income countries in 2009:

15 countries, including Botswana, Guyana and South Africa, were able to treat more than 80% of HIV-positive pregnant women

14 countries, including Brazil, Namibia and Ukraine, provided HIV treatment to more than 80% of HIV-positive children

8 countries, including Cambodia, Cuba and Rwanda, have achieved universal access to antiretroviral treatment (ART) for adults.

river blindness

35 million people world-wide suffer from disease

140 million African people are at risk

caused by a parasitical worm, onchocercavolvulus.

The worm larvae are spread by the black simulium fly, which breeds in the high-oxygen water of fast-flowing rivers.

fly transmits disease when it bites people, making those who live or work near the rivers vulnerable.

Treatment - Mectizan®.

River Blindness

Ways to break the cycle of infection:

reducing # of flies by spraying affected areas with insecticide

slowing fast-flowing rivers, making them unattractive as breeding grounds

reducing exposure to flies by using protective garments

killing the adult worms by removing the worm 'nodules' - difficult because infected villages are often very remote and poor, making accessible surgery difficult.

providing a yearly dose of the drug Mectizan® in affected areas.

Problems with medication

Needs to be administered regularly and communally


Most violent and sudden

Cause the highest # of deaths

July 27, 1976 – Tangshan China – killed 255,000 + 665,000 injured

Occur in areas of world defined by tectonic plates

Many run through highly populated areas

after effects

Collapsing buildings

Breaks in communication and transportation

Electricity loss




After Effects
more severe effects in ldcs and lldcs

High population density

Substandard housing

Lack relief resources

More Severe effects in LDCs and LLDCs

Cause fewer deaths than any other natural disaster

Slow – lots of warning

Well known volcanoes – Mt. Vesuvius (Pompeii), Mt. St. Helens (Washington State), Eyjafjallajökull(Iceland)

Hawaii has daily volcanic activity

Iceland has harnessed geothermal energy for heating and electricity generation

slides and avalanches

Slide is rapid movement down a slope – rocks, soil or combination

Combination of geological factors + triggering event like heavy rain or earthquake or human effect – deforestation, clearcutting

Avalanches – rapid movement of snow and ice

Slides and Avalanches

Japanese for “harbour wave”

Not connected to tides – therefore not “tidal waves”

Caused by mudflows, landslides, earthquakes or volcanoes that take place on ocean floor

Most common cause – earthquakes

Devastating tsunami – Thailand, Christmas 2004 – 230,000 deaths

the role of humans in natural disasters

We are victims of natural disasters

We can also cause them to be more disastrous

Clear cutting, hillside farming, urban development

The role of humans in natural disasters

http://visual.merriam-webster.com/images/plants-gardening/plants/plant/photosynthesis.jpg, retrieved March 1, 2010

http://www.allaboutgemstones.com/rock_cycle.html retrieved March 3, 2010

http://en.wikipedia.org/wiki/Earth March 3

http://www.bing.com/images/search?q=Tide&FORM=BIFD#focal=c753352f665971332d781ca13addc07e&furl=http%3A%2F%2Flibrary.thinkquest.org%2FC003124%2Fimages%2Ftides.jpg March 3

http://www.harcourtschool.com/activity/science_up_close/314/deploy/interface.html March 3

file:///H:\My%20Pictures\Hurricane_formation.gif retrieved March 11

file:///H:\My%20Pictures\flappy_tornado_formation.jpg retrieved March 11

National Geographic websites