Causes of Global Hazards

A2 Unit 5a

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.

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

Who studies Hazards

• Scientists• Geomorphologists• Geologists• Hydrologists• Structural engineers• Insurers• Public bodies• Economists

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

Causes of Hazards!!

• Bushfires• Tornadoes• Floods• Tectonic hazards• Landslides• Climate Change

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

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

How can Fires be Reduced?

• Controlled Burning• Education Programmes• Removal of leaf litter

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.

Damage?

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

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

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

Global Map of Predicted Drought

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

Example Floods

• Bocastle – UK• Mississippi – USA• Bangladesh – Asia

Tropical Storms

• Monsoons• Typhoons• Willy willies• Tropical Cyclones• Hurricanes

• All the same thing

• 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

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.

Plates and Movement

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

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

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.

• 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

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.

• 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.

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

• 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.

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

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.

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)

Link Between Population and Disasters

Causes and Amount

Good Luck!!!Don’t let yourself down