A natural hazard is a natural event or process which affects people e.g. Causing loss of
life or injury, economic damage, disruption to people’s lives or environmental
degradation.
For a natural event to become a hazard, it has to involve people.
Types of hazard:
Hydro-meteorological those caused by running water and its processes (hydro) and
those associated with or caused by weather patterns (meteorological). E.g. Floods,
hurricanes and drought.
Geophysical those caused by earth processes. There are two types:
Internal earth processes (tectonic) e.g. Earthquakes and volcanoes
External earth processes (geomorphological) e.g. Landslides or
rockslides
When does a natural hazard become a disaster?
Dregs model defines disasters as a matter of scale, simply bigger than a natural hazard.
Whether a hazard becomes a disaster can depend on how vulnerable people who are
exposed to it are.
Hazard Cause of hazard
Conservative margin When two plates move alongside eachother. Gives major
earthquakes e.g. San Andreas fault. Sudden movements from
Pressure.
Destructive margin Occur when oceanic crust collides with plates of continental
crust. Collision zone is subduction zone. Continental above
oceanic.
Pressure submerges plate. Descending plate is burned up to
form lava so earthquakes occur. Fold mountains. E.g.
Montserrat.
Constructive margin When plates move away from eachother, dragged by convection.
Magma rises to form oceanic crust. Volcanos and earthquakes
E.g. Iceland.
Collision margin Where plates of continental crust move towards eachother.
Edges buckle up to form mountains.
,Tsunamis Undersea earthquakes. Can be caused by seismic events. One
plate slips under another water is displaced vertically. Creates
Powerful waves.
Landslides Mountainous places prone. After abnormal rain and/or seismic
activity. Human factors e.g. Deforestation/building on hills.
Avalanches Concentrated in high mountainous areas. Global warming
increases.
Describing the distribution of earthquakes/volcanoes/slides
Earthquakes greater concentration at plate boundaries e.g. Eurasian plate. Pacific ring
of fire. Mid Atlantic ridge.
Volcanoes found along plate boundaries. Weaknesses in earth’s crust.
Slides located in north America/Europe/new Zealand. Mainly in mountainous regions.
Distribution and cause of hydro-meteorological hazards
Hurricanes are just above and just below the equator between the tropics. Greatest
activity over oceans. In warmer regions.
Drought/wildfire located in the tropic of cancer/Sahel/Australia/north America.
Hurricanes/tropical storms/cyclones/typhoons
Hazard a natural event that has an
adverse effect on people/environment.
Vulnerability denotes inadequate
means/ability to protect oneself.
Capacity refers to ability of
community to absorb/recover from the
effects.
Risk the expected number of lives
lost, persons injured, damage to
property and disruption to economy
due to natural disaster.
The world is becoming a more
risky place
El Nino and La Nina
El Niño is the appearance of warm surface
water from time to time in the eastern
equatorial pacific.
, It is found in Australia/oceana and Peru South America.
Usually, the wind blows strongly from east to west along the equator in the Pacific. This
actually piles up water in the western part of the Pacific. In the eastern part, deeper
water gets pulled up from below to replace the water pushed west. So, the normal
situation is warm water in the west, cold in the east. In an El Niño, the winds pushing
that water around get weaker. As a result, some of the warm water piled up in the west
slumps back down to the east, and not as much cold water gets pulled up from below.
Both these tend to make the water in the eastern Pacific warmer, which is one of the
hallmarks of an El Niño. The warmer ocean then affects the winds - it makes the winds
weaker, heating the water.
La Nina is the appearance of colder than
average sea surface temperatures in
the central and east equatorial pacific.
A deep layer of cooler than average
ocean temperatures across the east-
central equatorial Pacific, with sea-
surface temperatures generally below
average, and sub-surface temperatures
typically below average at the depth of
the oceanic thermocline.
A shallower than average oceanic
thermocline across the east-central
equatorial Pacific, with depths typically
ranging from 50-100 m.
It is approximately a 7 year cycle 1-2 years El Nino and 1-2 years La
Nina. Climatic patterns
Periodic weather changes. Drought/forest fires, other times
floods/landslides. EL NINO AND LA NINA
El Nino 7 year cycle (1-2 years are El Nino). Air currents move eastwards towards
the Pacific, bringing moist air to South America and East Pacific. Californian coast
affected – torrential rains, flooding and landslides.
La Nina 1-2 years. Current reverses to move across Pacific towards Australia bringing
moist air to Australia and west Pacific. Warm, dry air blows over California bringing
drought and forest fires.
Kashmir and Sichuan earthquakes compared
Sichuan earthquake Kashmir earthquake
Location China. Eurasian tectonic plate Lies in the area of collision of the Eurasian
(collision) And Indian tectonic plates.
, Hazard Magnitude 7.9. Afternoon Earthquake result of gradual geological
details weekday. Triggered landslides. movement. Secondary earthquakes. 147
Destruction of road network. aftershocks. Magnitude 7.6. +978 aftershocks
Over 4.
Vulnerability High dense population. Poorly built. Time of day = 8.50am Saturday. Devastation
Mountainous region – low may take a decade to repair. Many schools
development. and children killed. Mountainous. Conflict.
Ground shaking.
Capacity to Expensive rebuilding. Aid/funding. Aid – very remote so no aid. 500,000 people.
cope Demand for tents. Conflict weakened
response to capacity.
Death toll Death toll 90,000. Health centres Farmers lost harvest. Schools destroyed.
destroyed. Chemical factory. Loss of Infrastructure – regulations.
Facilities. Death toll 73,000.
The Philippines & Californian Coast – Hazard hotspot/multiple hazard zone – physical
and human causes and interaction of different hazards
Six most hazard prone in the world:
Philippines, India, Japan, Bangladesh, China, Indonesia
Philippines
It sits across a plate boundary so faces significant risks from volcanos/earthquakes. Its
northern and eastern coasts face the Pacific (the most tsunami-prone ocean). It lies
within south-east Asia’s major typhoon belts. Landslides are common in mountain
districts (mostly mountainous with coastal lowlands).
It is a middle income country.
Tectonic hazards lies between Philippine and Eurasian plates creating Manila ocean
trench. Plates move in series of jerks producing earthquakes each time. Destructive
plate boundary. Subducted Eurasian plate forms magma which solidifies over volcanos
vent so a lot of pressure.
Mount Pinatubo’s volcanic eruption in June 1991
Pyroclastic flows and lahars. 1st eruption sent ash clouds 20km. 2nd eruption was
cataclysmic, pyroclastic blast and huge lahars.
Effective monitoring so death and injury toll was +4300 people. 250 people died. Some
evacuees died in camps. 80,000 hectares of farmland buried by ash disrupting farmers
livelihoods. Economic loss was US$710 million.
Other hazard risks
Earthquake 2006
Killed 15 people, injured 100 and damaged 800 buildings. Local tsunami. Landslides
and consequential floods.
life or injury, economic damage, disruption to people’s lives or environmental
degradation.
For a natural event to become a hazard, it has to involve people.
Types of hazard:
Hydro-meteorological those caused by running water and its processes (hydro) and
those associated with or caused by weather patterns (meteorological). E.g. Floods,
hurricanes and drought.
Geophysical those caused by earth processes. There are two types:
Internal earth processes (tectonic) e.g. Earthquakes and volcanoes
External earth processes (geomorphological) e.g. Landslides or
rockslides
When does a natural hazard become a disaster?
Dregs model defines disasters as a matter of scale, simply bigger than a natural hazard.
Whether a hazard becomes a disaster can depend on how vulnerable people who are
exposed to it are.
Hazard Cause of hazard
Conservative margin When two plates move alongside eachother. Gives major
earthquakes e.g. San Andreas fault. Sudden movements from
Pressure.
Destructive margin Occur when oceanic crust collides with plates of continental
crust. Collision zone is subduction zone. Continental above
oceanic.
Pressure submerges plate. Descending plate is burned up to
form lava so earthquakes occur. Fold mountains. E.g.
Montserrat.
Constructive margin When plates move away from eachother, dragged by convection.
Magma rises to form oceanic crust. Volcanos and earthquakes
E.g. Iceland.
Collision margin Where plates of continental crust move towards eachother.
Edges buckle up to form mountains.
,Tsunamis Undersea earthquakes. Can be caused by seismic events. One
plate slips under another water is displaced vertically. Creates
Powerful waves.
Landslides Mountainous places prone. After abnormal rain and/or seismic
activity. Human factors e.g. Deforestation/building on hills.
Avalanches Concentrated in high mountainous areas. Global warming
increases.
Describing the distribution of earthquakes/volcanoes/slides
Earthquakes greater concentration at plate boundaries e.g. Eurasian plate. Pacific ring
of fire. Mid Atlantic ridge.
Volcanoes found along plate boundaries. Weaknesses in earth’s crust.
Slides located in north America/Europe/new Zealand. Mainly in mountainous regions.
Distribution and cause of hydro-meteorological hazards
Hurricanes are just above and just below the equator between the tropics. Greatest
activity over oceans. In warmer regions.
Drought/wildfire located in the tropic of cancer/Sahel/Australia/north America.
Hurricanes/tropical storms/cyclones/typhoons
Hazard a natural event that has an
adverse effect on people/environment.
Vulnerability denotes inadequate
means/ability to protect oneself.
Capacity refers to ability of
community to absorb/recover from the
effects.
Risk the expected number of lives
lost, persons injured, damage to
property and disruption to economy
due to natural disaster.
The world is becoming a more
risky place
El Nino and La Nina
El Niño is the appearance of warm surface
water from time to time in the eastern
equatorial pacific.
, It is found in Australia/oceana and Peru South America.
Usually, the wind blows strongly from east to west along the equator in the Pacific. This
actually piles up water in the western part of the Pacific. In the eastern part, deeper
water gets pulled up from below to replace the water pushed west. So, the normal
situation is warm water in the west, cold in the east. In an El Niño, the winds pushing
that water around get weaker. As a result, some of the warm water piled up in the west
slumps back down to the east, and not as much cold water gets pulled up from below.
Both these tend to make the water in the eastern Pacific warmer, which is one of the
hallmarks of an El Niño. The warmer ocean then affects the winds - it makes the winds
weaker, heating the water.
La Nina is the appearance of colder than
average sea surface temperatures in
the central and east equatorial pacific.
A deep layer of cooler than average
ocean temperatures across the east-
central equatorial Pacific, with sea-
surface temperatures generally below
average, and sub-surface temperatures
typically below average at the depth of
the oceanic thermocline.
A shallower than average oceanic
thermocline across the east-central
equatorial Pacific, with depths typically
ranging from 50-100 m.
It is approximately a 7 year cycle 1-2 years El Nino and 1-2 years La
Nina. Climatic patterns
Periodic weather changes. Drought/forest fires, other times
floods/landslides. EL NINO AND LA NINA
El Nino 7 year cycle (1-2 years are El Nino). Air currents move eastwards towards
the Pacific, bringing moist air to South America and East Pacific. Californian coast
affected – torrential rains, flooding and landslides.
La Nina 1-2 years. Current reverses to move across Pacific towards Australia bringing
moist air to Australia and west Pacific. Warm, dry air blows over California bringing
drought and forest fires.
Kashmir and Sichuan earthquakes compared
Sichuan earthquake Kashmir earthquake
Location China. Eurasian tectonic plate Lies in the area of collision of the Eurasian
(collision) And Indian tectonic plates.
, Hazard Magnitude 7.9. Afternoon Earthquake result of gradual geological
details weekday. Triggered landslides. movement. Secondary earthquakes. 147
Destruction of road network. aftershocks. Magnitude 7.6. +978 aftershocks
Over 4.
Vulnerability High dense population. Poorly built. Time of day = 8.50am Saturday. Devastation
Mountainous region – low may take a decade to repair. Many schools
development. and children killed. Mountainous. Conflict.
Ground shaking.
Capacity to Expensive rebuilding. Aid/funding. Aid – very remote so no aid. 500,000 people.
cope Demand for tents. Conflict weakened
response to capacity.
Death toll Death toll 90,000. Health centres Farmers lost harvest. Schools destroyed.
destroyed. Chemical factory. Loss of Infrastructure – regulations.
Facilities. Death toll 73,000.
The Philippines & Californian Coast – Hazard hotspot/multiple hazard zone – physical
and human causes and interaction of different hazards
Six most hazard prone in the world:
Philippines, India, Japan, Bangladesh, China, Indonesia
Philippines
It sits across a plate boundary so faces significant risks from volcanos/earthquakes. Its
northern and eastern coasts face the Pacific (the most tsunami-prone ocean). It lies
within south-east Asia’s major typhoon belts. Landslides are common in mountain
districts (mostly mountainous with coastal lowlands).
It is a middle income country.
Tectonic hazards lies between Philippine and Eurasian plates creating Manila ocean
trench. Plates move in series of jerks producing earthquakes each time. Destructive
plate boundary. Subducted Eurasian plate forms magma which solidifies over volcanos
vent so a lot of pressure.
Mount Pinatubo’s volcanic eruption in June 1991
Pyroclastic flows and lahars. 1st eruption sent ash clouds 20km. 2nd eruption was
cataclysmic, pyroclastic blast and huge lahars.
Effective monitoring so death and injury toll was +4300 people. 250 people died. Some
evacuees died in camps. 80,000 hectares of farmland buried by ash disrupting farmers
livelihoods. Economic loss was US$710 million.
Other hazard risks
Earthquake 2006
Killed 15 people, injured 100 and damaged 800 buildings. Local tsunami. Landslides
and consequential floods.
