Natural Hazards
Natural hazard – a natural event that has a negative effect on humans and the environment
TYPES OF NATURAL HAZARD: Atmospheric Geological
Rain Volcano
o Volcanic eruptions Lightning Mudflow
o Earthquakes Snow Landslide
o Storms Drought Avalanche
o Tsunamis Tornado Earthquake
o Landslides Hurricanes
Wind
o Floods
Hazard risk – the chance or probability of being affected by a natural event
FACTORS INCREASING THE RISK FROM NATURAL HAZARDS:
Urbanisation:
o More densely populated areas are at a greater risk
Climate Change:
o The atmosphere has more energy leading to more intense storms and hurricanes
o Can cause some parts of the world to become wetter – increased risk of flooding
o Other areas my become drier and prone to droughts and famines
Farming:
o When rivers flood, they deposit fertile silt on the floodplain
o This is good for farming
o Some people are at risk from the floods
o In low-lying countries there are many people that live on floodplains
Poverty:
o People may be forced to live in areas at risk due to a lack of money
o Shortages of housing leads to people building on unstable slopes prone to floods and
landslides
TECTONIC HAZARDS
Earthquake – a sudden violent period of ground shaking.
o Most caused by a sudden movement of rocks within the earth’s crust
o Along plate margins (e.g. western coast of North and South America)
o Some don’t occur at plate margins due to human activity (e.g. underground mining)
Volcano – a large and often conical-shaped landform usually formed over a long period of time by a
series of eruptions
o Occur along long belts that follow plate margins (e.g. around the edge of Pacific– ring of fire)
o Fed by hot magma that rises to the surface at constructive and destructive plate margins
, o Also form at hot spots – where crust is thin and magma is able to break through to surface
TECTONIC PLATES
o The earth’s crust is split into several plates about
100km thick
o Two types of crust – dense, thin oceanic crust and less
dense, thick continental crust
o Plates move in relation to each other due to
convection currents
CONSTRUCTIVE
- Two plates moving apart
o Magma forces its way to surface
o Breaks through crust and causes earthquakes
o Reaching the surface forms volcanoes
o Shield volcanoes
DESTRUCTIVE
- Two plates moving towards each other
o Where two plates meet a deep ocean trench
forms
o The denser plate is subducted beneath less
dense plate
o Friction causes earthquakes
o As oceanic plate moves downwards it melts
o This creates magma which is less fluid
o This breaks through to the surface to form
steep-sided composite volcanoes
Where two continental plates meet
there is no subduction
The two plates collide and the crust
becomes crumpled and uplifted
Forms fold mountains e.g. Himalayas
This causes earthquakes
No volcanoes as there is no magma
CONSERVATIVE
- Two plates moving past each other
o Friction between plates cause earthquakes
o Earthquakes can be destructive as they are
close to Earth’s surface
o No volcanoes as there is no magma
Natural hazard – a natural event that has a negative effect on humans and the environment
TYPES OF NATURAL HAZARD: Atmospheric Geological
Rain Volcano
o Volcanic eruptions Lightning Mudflow
o Earthquakes Snow Landslide
o Storms Drought Avalanche
o Tsunamis Tornado Earthquake
o Landslides Hurricanes
Wind
o Floods
Hazard risk – the chance or probability of being affected by a natural event
FACTORS INCREASING THE RISK FROM NATURAL HAZARDS:
Urbanisation:
o More densely populated areas are at a greater risk
Climate Change:
o The atmosphere has more energy leading to more intense storms and hurricanes
o Can cause some parts of the world to become wetter – increased risk of flooding
o Other areas my become drier and prone to droughts and famines
Farming:
o When rivers flood, they deposit fertile silt on the floodplain
o This is good for farming
o Some people are at risk from the floods
o In low-lying countries there are many people that live on floodplains
Poverty:
o People may be forced to live in areas at risk due to a lack of money
o Shortages of housing leads to people building on unstable slopes prone to floods and
landslides
TECTONIC HAZARDS
Earthquake – a sudden violent period of ground shaking.
o Most caused by a sudden movement of rocks within the earth’s crust
o Along plate margins (e.g. western coast of North and South America)
o Some don’t occur at plate margins due to human activity (e.g. underground mining)
Volcano – a large and often conical-shaped landform usually formed over a long period of time by a
series of eruptions
o Occur along long belts that follow plate margins (e.g. around the edge of Pacific– ring of fire)
o Fed by hot magma that rises to the surface at constructive and destructive plate margins
, o Also form at hot spots – where crust is thin and magma is able to break through to surface
TECTONIC PLATES
o The earth’s crust is split into several plates about
100km thick
o Two types of crust – dense, thin oceanic crust and less
dense, thick continental crust
o Plates move in relation to each other due to
convection currents
CONSTRUCTIVE
- Two plates moving apart
o Magma forces its way to surface
o Breaks through crust and causes earthquakes
o Reaching the surface forms volcanoes
o Shield volcanoes
DESTRUCTIVE
- Two plates moving towards each other
o Where two plates meet a deep ocean trench
forms
o The denser plate is subducted beneath less
dense plate
o Friction causes earthquakes
o As oceanic plate moves downwards it melts
o This creates magma which is less fluid
o This breaks through to the surface to form
steep-sided composite volcanoes
Where two continental plates meet
there is no subduction
The two plates collide and the crust
becomes crumpled and uplifted
Forms fold mountains e.g. Himalayas
This causes earthquakes
No volcanoes as there is no magma
CONSERVATIVE
- Two plates moving past each other
o Friction between plates cause earthquakes
o Earthquakes can be destructive as they are
close to Earth’s surface
o No volcanoes as there is no magma
