Ppt on most of the global hazards and how they are formed, plus some data and case studies on various types

1. Causes of Global Hazards
A2 Unit 5a

2. A Natural Event
• One where a natural hazard occurs but does not
affect people
• E.G. – Cause loss of life, injury, economic damage,
disruption to lives or environments.

3. Natural Disaster
• One which affects people, lives, environment or
economic damage.
• Whether a hazard becomes a disaster can depend
on how vulnerable the people who are exposed to
it are.
• Increasing number of people are becoming
vulnerable

4. Who studies Hazards
• Scientists
• Geomorphologists
• Geologists
• Hydrologists
• Structural engineers
• Insurers
• Public bodies
• Economists

5. How significant are Hazards?
• Though numbers vary less than 100,000 people die
a year from natural disasters
• 30 x less than the number who die from AIDS
• 35 x less than all road deaths
• 50 x less than number who die from smoking
related diseases

6. Causes of Hazards!!
• Bushfires
• Tornadoes
• Floods
• Tectonic hazards
• Landslides
• Climate Change

7. Bushfires - Australia
• Bushfires / Wild Fires are a natural part of wild land
renewal in Australia.
• They occur in many places around the world where
there is plenty of fuel; wood, leaves, forest or
brush, that can burn.
• 94% of bushfires are started by humans
• Canada also suffers from forest fires, along with
Many dry places, California, Africa, India

8. Causes of Wildfires
arson Lightning is the greatest cause in
Western Australia, Northern Territory
and western Queensland, due to
electric storms
Burning embers friction of trees and
sparks from power lines spontaneous combustion
sparks from mechanical sources spot fires can start up to 25 km from
the fire front
cigarette butts
camp fires
About half are a result of a burn-off
that gets out of hand

9. How can Fires be Reduced?
• Controlled Burning
• Education Programmes
• Removal of leaf litter

10. Tornadoes
• Brought about by circulating air around an area of low
pressure.
• Draw cold winds from polar regions to the north and
tropical winds from the south
• Air warms at surface, becomes lighter and starts to
rise, making it unstable
• This sets up small convection currents which rise
• Earth’s rotation causes air to spin
• Faster it spins, more likely to ‘touch down’ on earth’s
surface and cause the tornado.

11. Damage?
• High winds can damage crops, buildings
• Injury from falling debris
• Main areas for these are

12. Drought
• Extended period of lower than average
precipitation
• Generally extends over two or more growing
seasons
• Can be localised, national or even effect a whole
continent.
• Areas most affect by drought are: Large parts of
Africa, Central Asia and most of Australia

13. Sahel
• Soils become exposed to wind erosion due to loss
of vegetation
• Nutrient rich top-soils lost affects capacity to cope
• Drought is a re-occurring experience.
• Worst 1972 -1984 – 100,000 died and many
dependant on aid
• Desertification

14. Global Map of Predicted Drought

15. Floods
• Dry land becomes inundated with water after
prolonged rainfall
• Floods occur in dry regions that lie downstream of
regions affected by heavy rain
• Bangladesh is prone to flooding from melt waters of
mountains in India and Nepal
• Egyptians thrived after learning how to manage
floodwaters
• Floods occur on every continent

16. Example Floods
• Bocastle – UK
• Mississippi – USA
• Bangladesh – Asia

17. Tropical Storms
• Monsoons
• Typhoons
• Willy willies
• Tropical Cyclones
• Hurricanes
• All the same thing

18. • They occur within 5 – 20o North or South of Equator
• Occur over warm oceans (At least 20o C and 70m
deep) 5o north or south of equator as Coriolis effect
weak at equator
• Damage crops, housing, flooding, high winds –
Hurricane Katrina

19. Earthquakes
• Geophysical hazard – physical processes that act
upon the earth
• Range from very slight tremors to catastrophic
events
• Caused by movement of rock within the
lithosphere.

20. Plates and Movement

21. Technical Bit
• Plates ‘float’ on a layer of semi-molten rock
(mantle)
• Heat generated by earth’s core moves the plates
via ‘convection currents’
• This is called ‘Continental Drift’
• They then collide, move away or slide passed each
other – Thus earthquakes are formed

22. Zones
• Earthquakes are one of the few natural hazards that
happen within zones
• They most often occur in areas of the world where most
tectonic activity occurs.
• In countries close to proximity of plate boundaries –
Japan, California
• Large quakes are relatively rare but people who live in
these zones often practice procedures designed to keep
them safe in MEDC’s

23. Volcanoes
• An opening of the earth’s crust that projects
material.
• Magma (Becomes lava upon contact with ground)
• Volcanic gases (hydrogen Sulphide)
• Ash, dust
• ‘Active’ – implies they are showing signs or are
erupting.

24. • The result of tectonic activity and are zonal.
• Main zone is the ‘pacific rim or ‘Ring of Fire’
• Rocks extruded are mineral and nutrient rich and
sought after by miners and farmers
• This explains why history shows us that many people
have settled near to active volcanoes
• 20m people live within 20km of Vesuvius in Italy
• Lava flows help create new land e.g. Iceland
• Extinct volcanoes are not expected to erupt but can
e.g. – Fourpeaks in Alaska 2006

26. Mount Pinatubo –
Volcano Case Study
• one of the 22 active volcanoes dotting the Philippines, is part of the
chain of volcanoes which borders the western side of Luzon and lies in
the central portion of the Zambales range
• It is an active stratovolcano
• The colossal 1991 eruption had a Volcanic Explosivity Index (VEI) of 6,
and came some 450–500 years after the volcano's last known eruptive
activity.
• Successful predictions of its led to the evacuation of tens of thousands
of people from the surrounding areas, saving many lives. Surrounding
areas were severely damaged by Pyroclastic flows, ash deposits and
later by lahars caused by rainwater remobilizing volcanic deposits:
thousands of buildings were destroyed.
• The effects of the eruption were felt worldwide.

27. • It ejected roughly
10 billion metric tonnes
of magma, and
20 million tons of SO2,
bringing vast quantities
of minerals and metals
to the surface
environment. It injected
large amounts of
aerosols into the
stratosphere—more
than any eruption since
that of Krakatoa in
1883.
• Over the following
months, the aerosols
formed a global layer of
sulphuric acid haze.
Global temperatures
dropped by about
0.5 °C (0.9 °F), and
ozone depletion
temporarily increased
substantially.

28. Landslides and Avalanches
• Landslides can occur anywhere
• Avalanches generally refer to snow or ice
• Are usually triggered by an event – heavy rainfall,
earthquake, road cutting other earthworks
• Often occur in the tropics due to Hurricanes and
monsoons.
• Vegetation clearing and deforestation can make it
worse

29. • Avalanches happen due to changes in
temperature, tectonic activity, noise generated and
are often slab falls where lighter new snow is
unstable on top of older more compacted snow.

30. Climate Change
• Hazards seen so far are nearly all isolated to a certain
place, Global warming is considered a context or
chronic hazard because it will effect everyone.
• Caused by Enhanced greenhouse gases generated
from anthropogenic (human) activity.
• Worst effects felt by those who have a low capacity to
cope
• Causes of hydro-meteorlogical disasters will increase
due to climate change

31. Injustice
• World’s most developed nations usually provide aid
and aid to the poorest who are most affected by
natural disasters.
• Climate change can not be solved by the
developed world alone
• Requires world reduction in EGHG
• Developed world got rich off off industrialisation
and the GHG it emitted.
• The developing world have yet to do this fully.

32. Political Attempts to stop this
• United Nations Environment Program (UNEP)
• Intergovernmental Panel on Climate Change
(IPCC)
• Earth Summit 1992
• Kyoto Protocol (Came into effect 2005)

34. Link Between Population and Disasters

35. Causes and Amount