Transcript Natural Hazard - G. Lombardo Radice

Natural Hazard
Is a threat of a naturally occurring event that will have a
negative effect on people or the environment.
Natural Disaster
A major natural hazard event that causes widespread
disruption to a community.
Structure of the Earth
Crust
The outer layer of the
earth. It is a thin layer
between 0-60 km thick.
The crust is the solid
rock layer upon which
we live.
Mantle
The widest section. It
has a thickness of
approximately 2,900
km. The mantle is made
up of semi-molten rock
called magma. In the
upper parts of the
mantle the rock is hard,
but lower down the
rock is soft and
beginning to melt.
Outer Core
The layer surrounding
the inner core. It is a
liquid layer, made up of
iron and nickel. It is still
extremely hot, with
temperatures similar to
the inner core.
Oceanic Crust – Carries the seas = younger, denser
(heavier), thinner and can be made & destroyed.
Continental Crust – Carries the land = older, less
dense (lighter), thicker and cannot be made or
destroyed.
Inner Core
The centre and is the
hottest part of the
Earth. It is solid, made
up of iron and nickel
with temperatures of
up to 5,500°C. With its
immense heat energy,
the inner core is like the
engine room of the
Earth.
Tectonic Plates
https://www.youtub
e.com/watch?v=zocu
tif0cQY
Convection Currents
1. Magma (semi-molten rock) near the outer
core is heated.
2. As the magma warms it expands and
becomes less dense.
3. The less dense magma then starts to rise
towards the crust.
4. As the magma nears the crust it begins to
cool.
5. The cooling magma becomes denser and
begins to sink.
6. The rising and falling magma creates
circular currents with the mantle.
https://www.youtube.com/watch?v=rSzjFvMFQhg
7. It are these currents that create friction
with the crust above and causes it to move.
1. Constructive Plate Boundaries
• A constructive plate boundary,
is where plates move apart
from each other. As they do
this, magma wells up to fill the
gap and when it reaches the
surface new crust is formed,
often in the form of a volcano.
• Overtime, ridges can break the
surface and form new islands,
e.g. Iceland.
• The Mid Atlantic Ridge was
formed due to constructive
plate movement.
2. Destructive Plate Boundaries
• A destructive plate boundary occurs when
oceanic and continental crusts move
towards each other.
• The oceanic plate is pushed underneath the
continental plate because it is heavier, this
forms the subduction zone.
• The friction of these plates rubbing against
each other causes melting of the oceanic
plate and can cause earthquakes.
• Magma from deep in the Earth’s mantle rises
towards the surface through the cracks and
erupts at the surface and a volcano can
form.
• Nazca and South American plates. The Nazca
plate is forced under the South American
plate.
3. Collision Plate Boundary
•
•
This type of plate boundary
involves two continental plates
colliding with each other.
Neither plate can be forced
under the other because they
are both lighter continental
crust, so both are forced up.
This process forms fold
mountains.
For example, the Himalayas
were formed by a collision
plate boundary.
4. Conservative Plate Boundaries
• A conservative plate boundary,
occurs when plates move
alongside each other, in the
opposite direction or in the same
direction at different speeds.
When plates slip past each other
creating sudden movement the
result is an earthquake.
• The San Andreas Fault in
California (USA) is an example of a
conservative plate boundary.
Volcanoes
Volcanoes are often cone shaped, formed by material from the
mantle being forced through an opening in the Earth’s crust.
Volcanoes are either . . .
Extinct
Dormant
Active
It will never erupt again.
E.g. Devil’s Tower, Wyoming
USA
It hasn’t erupted in 2000 years.
E.g. Mt. Kilimanjaro, Tanzania
It has erupted recently and
it is likely to erupt again.
E.g. Mt. Etna, Sicily.
An eruption
occurs when
pressure in the
magma
chamber
forces magma
up the main
vent, towards
the crater at
the top of the
volcano. Some
magma will
also be forced
out of the
secondary vent
at the side of
the volcano.
Features of a Volcano
Types of Volcanoes
Shield Volcanoes
Composite Volcanoes
• Found at constructive or tensional
boundaries.
• They are low, with gently sloping
sides.
• They are formed by eruptions of thin,
runny lava.
• Eruptions tend to be frequent but
relatively gentle
• Made up of alternating layers of lava
and ash (other volcanoes just consist
of lava).
• They are usually found at destructive
or compressional boundaries.
• The eruptions from these volcanoes
may be a pyroclastic flow rather than
a lava flow. A pyroclastic flow is a
mixture of hot steam, ash, rock and
dust.
• A pyroclastic flow can roll down the
sides of a volcano at very high speeds
and with temperatures of over 400°C.
Effects of Volcanoes
If the ash and mud from a volcanic eruption
mix with rain water or melting snow, fast
moving mudflows are created. These flows
are called lahars.
Lava flows and lahars can destroy
settlements and clear areas of woodland or
agriculture.
Human and natural landscapes can be
destroyed and changed forever.
LEDC’s are more Vulnerable than MEDC’s
• Communication systems may be underdeveloped, so the
population may not be well educated about what to do in
the event of a volcanic eruption or an earthquake.
• Construction standards tend to be poor in LEDCs. Homes
and other buildings may suffer serious damage when a
disaster occurs.
• Buildings collapsing can cause high death tolls.
• Evacuation and other emergency plans can be difficult to
put into action due to limited funds and resources.
• Clearing up can be difficult. There may not be enough
money to rebuild homes quickly and safely. Many people
could be forced to live in emergency housing or refugee
camps.
Good Planning Reduces the Effect of Hazards
1. Diversion channels: On some volcanoes it has been attempted to make diversion channels to direct the lava away from
settlements. This is very expensive and hard because you can not predict which direction the lava will flow.
2. Cooling lava: In Iceland in the past they have tried spraying seawater onto lava. The idea was to make the lava go cold and
turn into rock before it destroyed nearby settlements.
3. Sweeping roofs: If this is not done the ash will get so heavy that it will eventually cause the building to collapse.
4. Making evacuation routes: It is also important to regularly practice these evacuation routes.
5. Exclusion areas: If an eruption is happening or likley to happen it is important to create exclusion zones. This means
evacuating everyone that could be effected by the eruption. Because pyroclastic flows can travel up to 30km, these
exclusion zones can be very big.
6. Hazard Mapping: It is very important to map the most dangerous areas near a volcano e.g. areas with the most unstable
ground or areas where lava flows are likley to travel. Once you have mapped dangerous areas you can then stop
settlements being built on them.
7. Monitoring volcanoes: Because volcanoes do give warning signs (change in shape, temperature, etc.) it is very important
to monitor them carefully so that you can nearby residents warnings.
8. Looking at volcanic history (previous eruptions and flows): As part of monitoring the volcano you can look at its history
and previous flows. You can then try calculate frequencies and areas likely to be effected.
Earthquakes
Earthquakes occur at Converging or Transform
Plate Boundaries.
As the plates move towards each other, they get stuck. This causes
pressure on the surrounding rocks. When this pressure is released it
produces strong shockwaves called seismic waves. This is an Earthquake.
The size of an Earthquake is measured using the Richter Scale.
Vibrations are recorded and measured using a Seismometer.
It is a Logarithmic scale, so an Earthquake with a measurement of 5 is 10 times
stronger than one of 4.
Most serious Earthquakes are between 5 -9 on the Richter Scale.
Richter Scale and Possible
Effects
Features of an Earthquake
The Focus = the
point where the
Earthquake starts,
the source of the
seismic waves. Near
the Focus the waves
are stronger and
cause more damage.
The Epicentre is
the point on the
Earth’s surface
immediately above
the Focus.
Energy is released
in Seismic Waves.
Aftershock is a
smaller Earthquake
that happens after
the main
Earthquake.
An Earthquake is a Primary Hazard.
Can cause Secondary Hazards – Tsunamis, Fire, Dam failure,
Landslides.
The affect an earthquake has on humans can depend on
numerous human and physical factors. These factors include:
1. The depth of the earthquake
2. The magnitude of the earthquake
3. The duration of the earthquake
4. The local geology (soft or hard rock, solid or cracked rock)
5. The location of the epicentre (in a rural or urban area)
6. The population density around the epicentre.
7. The building design and hazard mapping near the epicentre.
8. The time of day
9. The preparedness of the population (evacuation routes,
emergency services, etc.)
10. The level of development – LEDC’s suffer more than MEDC’s.
Vulnerability
Effects of an Earthquake
Social impacts
Economic impacts
Environmental impacts
The built landscape
People may be killed or Shops and business
may be destroyed.
injured. Homes may be may be destroyed.
Fires can spread due to
destroyed. Transport Looting may take place. gas pipe explosions.
Short-term (immediate) and communication
The damage to
Fires can damage areas
impacts
links may be disrupted. transport and
of woodland.
Water pipes may burst communication links Landslides may occur.
and water supplies may can make trade
Tsunamis may cause
be contaminated.
difficult.
flooding in coastal
areas.
The cost of rebuilding a
settlement is high.
Disease may spread.
Investment in the area
Important natural and
People may have to be may be focused only on
Long-term impacts
human landmarks may
re-housed, sometimes repairing the damage
be lost.
in refugee camps.
caused by the
earthquake. Income
could be lost.
Effects of Volcanoes
If the ash and mud from a volcanic eruption
mix with rain water or melting snow, fast
moving mudflows are created. These flows
are called lahars.
Lava flows and lahars can destroy
settlements and clear areas of woodland or
agriculture.
Human and natural landscapes can be
destroyed and changed forever.
LEDC’s are more Vulnerable than MEDC’s
• Communication systems may be underdeveloped, so the
population may not be well educated about what to do in
the event of a volcanic eruption or an earthquake.
• Construction standards tend to be poor in LEDCs. Homes
and other buildings may suffer serious damage when a
disaster occurs.
• Buildings collapsing can cause high death tolls.
• Evacuation and other emergency plans can be difficult to
put into action due to limited funds and resources.
• Clearing up can be difficult. There may not be enough
money to rebuild homes quickly and safely. Many people
could be forced to live in emergency housing or refugee
camps.
Good Planning Reduces the Effect of Hazards
1. Diversion channels: On some volcanoes it has been attempted to make diversion channels to direct the lava away from
settlements. This is very expensive and hard because you can not predict which direction the lava will flow.
2. Cooling lava: In Iceland in the past they have tried spraying seawater onto lava. The idea was to make the lava go cold and
turn into rock before it destroyed nearby settlements.
3. Sweeping roofs: If this is not done the ash will get so heavy that it will eventually cause the building to collapse.
4. Making evacuation routes: It is also important to regularly practice these evacuation routes.
5. Exclusion areas: If an eruption is happening or likley to happen it is important to create exclusion zones. This means
evacuating everyone that could be effected by the eruption. Because pyroclastic flows can travel up to 30km, these
exclusion zones can be very big.
6. Hazard Mapping: It is very important to map the most dangerous areas near a volcano e.g. areas with the most unstable
ground or areas where lava flows are likley to travel. Once you have mapped dangerous areas you can then stop
settlements being built on them.
7. Monitoring volcanoes: Because volcanoes do give warning signs (change in shape, temperature, etc.) it is very important
to monitor them carefully so that you can nearby residents warnings.
8. Looking at volcanic history (previous eruptions and flows): As part of monitoring the volcano you can look at its history
and previous flows. You can then try calculate frequencies and areas likely to be effected.
Earthquakes
Earthquakes occur at Converging or Transform
Plate Boundaries.
As the plates move towards each other, they get stuck. This causes
pressure on the surrounding rocks. When this pressure is released it
produces strong shockwaves called seismic waves. This is an Earthquake.
The size of an Earthquake is measured using the Richter Scale.
Vibrations are recorded and measured using a Seismometer.
It is a Logarithmic scale, so an Earthquake with a measurement of 5 is 10 times
stronger than one of 4.
Most serious Earthquakes are between 5 -9 on the Richter Scale.
Richter Scale and Possible
Effects
Features of an Earthquake
The Focus = the
point where the
Earthquake starts,
the source of the
seismic waves. Near
the Focus the waves
are stronger and
cause more damage.
The Epicentre is
the point on the
Earth’s surface
immediately above
the Focus.
Energy is released
in Seismic Waves.
Aftershock is a
smaller Earthquake
that happens after
the main
Earthquake.
An Earthquake is a Primary Hazard.
Can cause Secondary Hazards – Tsunamis, Fire, Dam failure,
Landslides.
The affect an earthquake has on humans can depend on
numerous human and physical factors. These factors include:
1. The depth of the earthquake
2. The magnitude of the earthquake
3. The duration of the earthquake
4. The local geology (soft or hard rock, solid or cracked rock)
5. The location of the epicentre (in a rural or urban area)
6. The population density around the epicentre.
7. The building design and hazard mapping near the epicentre.
8. The time of day
9. The preparedness of the population (evacuation routes,
emergency services, etc.)
10. The level of development – LEDC’s suffer more than MEDC’s.
Vulnerability
Effects of an Earthquake
Social impacts
Economic impacts
Environmental impacts
The built landscape
People may be killed or Shops and business
may be destroyed.
injured. Homes may be may be destroyed.
Fires can spread due to
destroyed. Transport Looting may take place. gas pipe explosions.
Short-term (immediate) and communication
The damage to
Fires can damage areas
impacts
links may be disrupted. transport and
of woodland.
Water pipes may burst communication links Landslides may occur.
and water supplies may can make trade
Tsunamis may cause
be contaminated.
difficult.
flooding in coastal
areas.
The cost of rebuilding a
settlement is high.
Disease may spread.
Investment in the area
Important natural and
People may have to be may be focused only on
Long-term impacts
human landmarks may
re-housed, sometimes repairing the damage
be lost.
in refugee camps.
caused by the
earthquake. Income
could be lost.
Good Planning Reduces the Effect of Hazard
Earthquakes are harder to predict, but there seem to be some clues – changes in well
water levels, gas emissions, cracks appearing in rocks, and strange animal behaviour
observed by Chinese Scientists in 1974.
• Disaster Plans
• Public Information
• Local Emergency Services are well prepared.
• Earthquake Proof Buildings.
• Strengthened Roads and Railways.
• Emergency Supplies of Water and Food.
Opportunities?
Volcanoes and Earthquakes aren’t all bad . . .
1. Beautiful environment – attracts tourists.
2. Volcanic Lava and Ash break down to form the most fertile soils on Earth =
Good for farming.
3. Precious Minerals and Fossil Fuels are found in Volcanic zones.
4. Land is cheap in Volcanic and Earthquake zones and people feel safer with
technological advances, such as “Earthquake proof” buildings.
5. Opportunities for cheap, renewable energy sources, such as Geothermal Energy
e.g. Iceland.
6. Hot springs nearby.
7. Many Earthquake zones are near the coast, and offer a good climate and easy
fishing.
Big events are rare, so people think they can risk it.
Tsunamis
A tsunami is a huge wave, usually caused by
volcanic or earthquake activity under the ocean,
which can eventually crash onto the shoreline.
The effects on a community can be devastating.
= Secondary Effect
Features of a Tsunami
When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms
the start of the tsunami.
When the waves reach shallower water:
•their height can increase by several metres
•the shallow water slows the wave
•the waves get closer together
It is hard to see that a tsunami is approaching. The most obvious sign is the coastal water retreats just
before the waves reach the shore.
Effects of a Tsunami
= Coastal Flooding
Economic
Effects
Social Effects
Environmental
Effects
Effects of Volcanoes
If the ash and mud from a volcanic eruption
mix with rain water or melting snow, fast
moving mudflows are created. These flows
are called lahars.
Lava flows and lahars can destroy
settlements and clear areas of woodland or
agriculture.
Human and natural landscapes can be
destroyed and changed forever.
LEDC’s are more Vulnerable than MEDC’s
• Communication systems may be underdeveloped, so the
population may not be well educated about what to do in
the event of a volcanic eruption or an earthquake.
• Construction standards tend to be poor in LEDCs. Homes
and other buildings may suffer serious damage when a
disaster occurs.
• Buildings collapsing can cause high death tolls.
• Evacuation and other emergency plans can be difficult to
put into action due to limited funds and resources.
• Clearing up can be difficult. There may not be enough
money to rebuild homes quickly and safely. Many people
could be forced to live in emergency housing or refugee
camps.
Good Planning Reduces the Effect of Hazards
1. Diversion channels: On some volcanoes it has been attempted to make diversion channels to direct the lava away from
settlements. This is very expensive and hard because you can not predict which direction the lava will flow.
2. Cooling lava: In Iceland in the past they have tried spraying seawater onto lava. The idea was to make the lava go cold and
turn into rock before it destroyed nearby settlements.
3. Sweeping roofs: If this is not done the ash will get so heavy that it will eventually cause the building to collapse.
4. Making evacuation routes: It is also important to regularly practice these evacuation routes.
5. Exclusion areas: If an eruption is happening or likley to happen it is important to create exclusion zones. This means
evacuating everyone that could be effected by the eruption. Because pyroclastic flows can travel up to 30km, these
exclusion zones can be very big.
6. Hazard Mapping: It is very important to map the most dangerous areas near a volcano e.g. areas with the most unstable
ground or areas where lava flows are likley to travel. Once you have mapped dangerous areas you can then stop
settlements being built on them.
7. Monitoring volcanoes: Because volcanoes do give warning signs (change in shape, temperature, etc.) it is very important
to monitor them carefully so that you can nearby residents warnings.
8. Looking at volcanic history (previous eruptions and flows): As part of monitoring the volcano you can look at its history
and previous flows. You can then try calculate frequencies and areas likely to be effected.
Earthquakes
Earthquakes occur at Converging or Transform
Plate Boundaries.
As the plates move towards each other, they get stuck. This causes
pressure on the surrounding rocks. When this pressure is released it
produces strong shockwaves called seismic waves. This is an Earthquake.
The size of an Earthquake is measured using the Richter Scale.
Vibrations are recorded and measured using a Seismometer.
It is a Logarithmic scale, so an Earthquake with a measurement of 5 is 10 times
stronger than one of 4.
Most serious Earthquakes are between 5 -9 on the Richter Scale.
Richter Scale and Possible
Effects
Features of an Earthquake
The Focus = the
point where the
Earthquake starts,
the source of the
seismic waves. Near
the Focus the waves
are stronger and
cause more damage.
The Epicentre is
the point on the
Earth’s surface
immediately above
the Focus.
Energy is released
in Seismic Waves.
Aftershock is a
smaller Earthquake
that happens after
the main
Earthquake.
An Earthquake is a Primary Hazard.
Can cause Secondary Hazards – Tsunamis, Fire, Dam failure,
Landslides.
The affect an earthquake has on humans can depend on
numerous human and physical factors. These factors include:
1. The depth of the earthquake
2. The magnitude of the earthquake
3. The duration of the earthquake
4. The local geology (soft or hard rock, solid or cracked rock)
5. The location of the epicentre (in a rural or urban area)
6. The population density around the epicentre.
7. The building design and hazard mapping near the epicentre.
8. The time of day
9. The preparedness of the population (evacuation routes,
emergency services, etc.)
10. The level of development – LEDC’s suffer more than MEDC’s.
Vulnerability
Effects of an Earthquake
Social impacts
Economic impacts
Environmental impacts
The built landscape
People may be killed or Shops and business
may be destroyed.
injured. Homes may be may be destroyed.
Fires can spread due to
destroyed. Transport Looting may take place. gas pipe explosions.
Short-term (immediate) and communication
The damage to
Fires can damage areas
impacts
links may be disrupted. transport and
of woodland.
Water pipes may burst communication links Landslides may occur.
and water supplies may can make trade
Tsunamis may cause
be contaminated.
difficult.
flooding in coastal
areas.
The cost of rebuilding a
settlement is high.
Disease may spread.
Investment in the area
Important natural and
People may have to be may be focused only on
Long-term impacts
human landmarks may
re-housed, sometimes repairing the damage
be lost.
in refugee camps.
caused by the
earthquake. Income
could be lost.
Good Planning Reduces the Effect of Hazard
Earthquakes are harder to predict, but there seem to be some clues – changes in well
water levels, gas emissions, cracks appearing in rocks, and strange animal behaviour
observed by Chinese Scientists in 1974.
• Disaster Plans
• Public Information
• Local Emergency Services are well prepared.
• Earthquake Proof Buildings.
• Strengthened Roads and Railways.
• Emergency Supplies of Water and Food.
Opportunities?
Volcanoes and Earthquakes aren’t all bad . . .
1. Beautiful environment – attracts tourists.
2. Volcanic Lava and Ash break down to form the most fertile soils on Earth =
Good for farming.
3. Precious Minerals and Fossil Fuels are found in Volcanic zones.
4. Land is cheap in Volcanic and Earthquake zones and people feel safer with
technological advances, such as “Earthquake proof” buildings.
5. Opportunities for cheap, renewable energy sources, such as Geothermal Energy
e.g. Iceland.
6. Hot springs nearby.
7. Many Earthquake zones are near the coast, and offer a good climate and easy
fishing.
Big events are rare, so people think they can risk it.
Tsunamis
A tsunami is a huge wave, usually caused by
volcanic or earthquake activity under the ocean,
which can eventually crash onto the shoreline.
The effects on a community can be devastating.
= Secondary Effect
Features of a Tsunami
When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms
the start of the tsunami.
When the waves reach shallower water:
•their height can increase by several metres
•the shallow water slows the wave
•the waves get closer together
It is hard to see that a tsunami is approaching. The most obvious sign is the coastal water retreats just
before the waves reach the shore.
Effects of a Tsunami
= Coastal Flooding
Economic
Effects
Social Effects
Environmental
Effects
Good Planning Reduces the Effect of Hazards
• Knowledge and Education
• Warning Systems
• Communication
• Natural Barriers
• Disaster Planning
Causes of Flooding
A flood occurs when a river bursts its banks and the water spills onto the
floodplain. Flooding tends to be caused by heavy rain: the faster the
rainwater reaches the river channel, the more likely it is to flood. The nature
of the landscape around a river will influence how quickly rainwater reaches
the channel.
• A steep-sided channel - a river channel surrounded by steep slopes causes fast surface
run-off.
• A lack of vegetation or woodland - trees and plants intercept precipitation (ie they
catch or drink water). If there is little vegetation in the drainage basin then surface
run-off will be high.
• A drainage basin, consisting of mainly impermeable rock - this will mean that water
cannot percolate through the rock layer, and so will run faster over the surface.
• A drainage basin in an urban area - these consist largely of impermeable concrete,
which encourages overland flow. Drains and sewers take water quickly and directly to
the river channel. Houses with sloping roofs further increase the amount of run-off.
Flooding is a natural process, which only becomes a hazard when it has a direct or
indirect effect upon the lives of people. This typically happens in the lower course of a
river and is why flood plains are created by the river.
Effects of Flooding
Social Effects
Economic Effects
Environmental Effects
Who is more Vulnerable?
Flood Management
Soft Engineering
• Afforestation.
• Planned Flooding.
• Warning Systems.
Hard Engineering
• Dam Construction. (Water is released in a
controlled way and can produce electricity)
• Straightening River Channels.
• Deepening River Channels. (Could have
effects downstream)
• Preventing Urban development.
Strategies need to be Sustainable
Opportunities?
• Rivers deposit rich silt on fields = fertile – good for
agriculture (Irrigation).
• Rivers can be used for Transport/Communication
• Leisure Activities = Tourism
• Settlement = Flat building land and provide Clay.
• Fishing
• Hydro Electric Power
Migration
As a Consequence of Natural
Hazards
Key terms:
Regional Migration (Internal) - When people move between regions of
the same country, e.g. Rural – Urban Migration, Counter-urbanisation.
International Migration (External) – When people move from one
country to another, e.g. Economic migrants, Refugees.
Emigrant Someone moving
OUT of a country.
Push
Factors
Migrant – The
person moving.
Pull
Factors
Immigrant –
Someone moving
INTO a country.
Key Terms:
Migration happens because of Push and Pull factors.
Push Factors – These are the things about the origin that make
someone decide to move. They are usually negative, e.g. lack of jobs or
education opportunities.
Pull Factors – These are the things about the destination that attract
people. They are usually positive things, e.g. job opportunities or the
perception of a better standard of living.
Usually a COMBINATION of the two factors causes Migration.
Natural Hazards Push people away
Natural Hazards displace people.
People are made homeless, businesses devastated and communities
destroyed.
People are made Refugees.
Refugee = a person who has been forced to leave their country in
order to escape war, persecution, or natural disaster.
19.5 million Refugees Worldwide
Revision
• Answer the Question!!!
 Careful and correct use of Geographical terms.
 Use data from valid sources – Statistics and Case Studies!
Clear presentation of points.
 Clear, balanced conclusions.
Inter relationships!
Paper 1 = ONLY ANSWER 3 QUESTIONS!!!!