Sunday, 1 January 2017
Geography revision
Naturals Hazards
- A natural hazard is an event which has a significant social impact.examples of natural
hazards are Earthquakes, landslides and flooding.They can be categorised as
atmospheric hazards , flooding and geological hazards
- A natural event becomes a natural hazard when the lives of people or property are in
danger.
- More people will be affected by flooding than any other hazard groups as lots of
densely populated cities lie on the banks of major rivers , like Dhaka which is
surrounded by many tributaries of the Ganges river in Bangladesh.Dhaka has a
population density of 45000 people/km2
- the main risk factors associated with an increase in the amount of natural hazards per
year are urbanisation ,as more people migrate into cities. with an increased population
density many large cities are in danger of a catastrophic natural hazard. Global
warming induced climate change brings rising sea levels and a runway sea and land
global temperature median give typhoons like Haiyan in 2013 more wind velocity and
tsunamis like the 2011 Japanese tsunami higher waves which creates havoc for those
living in coastal areas. Farming also drives many people to floodplains of rivers were
to river brings up nutrient rich sediment and silt from the river bed which gives farmers
better crop yields. In flat low lying areas this is deadly like the ganges delta and
floodplain in Bangladesh. In LEDC’s building companies use cheap materials instead
of actual materials due to lack of subsidy from governments to complete substandard,
haphazard infrastructure which are waiting to be exposed by a minor natural hazard
like in Taiwan where a 17 storey building collapsed after a 6.4 magnitude earthquake
leaving empty vegetable oil cans visible in the foundations. All these factor intertwine
to create a good chance for massive catastrophe in large cities as urbanisation drives
people to large cities to look for employment opportunities. mass poverty forces
building companies to use substandard materials to complete ‘relief’ infrastructure to
house as many people as possible and farming draws people out tO coastal areas
where land is plentiful and fertile but climate change brings rising sea levels which can
often devastate huge swaths of coastal land.
- When answering a photo question look for evidence of impacts and think
about what people there do for livelihood.and the economic state of the
1
, Sunday, 1 January 2017
country being observed.As well as how the disaster has affected them
socially and environmentally and whether any of these points link together
Tectonic Hazards
- A tectonic plate is a section of the Earths crust, there are two types of tectonic plates; the
dense - thin oceanic crust (basalt) , and the less dense - thicker continental crust (granite)
- Plates move due to convection currents deep inside the mantle where liquid magma drags
plates towards each other , or away from each other .
- Volcanoes are a type of natural hazard produced when magma from deep inside the earth
rises, upon reaching the surface the magma cools and solidifies forming huge composite
volcanoes, these volcanoes are produced at destructive plates boundaries where magma is
more viscous and has a higher silica content as well as more rock minerals and water vapour
dissolved in it. this means on breaching the crust the magma doesn't flow far and stacks in a
short radius(andes range).however shield volcanoes are produced at constructive boundaries
as the magma has a low viscosity and a low silica and mineral content, this means on
breaching the oceanic trench the lava flows relatively long distances and forms gently sloping
and flat shield volcanoes, like (Mt Kilauea)
- Earthquakes are a type of natural hazard and occur at plate boundaries when plates slip and
discharge huge amounts of tension built up of over hundreds of years.
- the global distribution of Earthquakes are mainly concentrated on plate boundaries, around
90% of earthquakes happen on or around the Pacific ring of fire; like on the San Andreas fault
on the American west coast. Very few earthquakes defy this generalisation, but one exception
are the Earthquakes produced in the Himalayas which is a collision zone. All recorded
earthquakes follow a linear pattern.An earthquake zone which follows all of the general trend s
are the earthquakes produced in the ocean and land surrounding or in Japan.
- At a constructive plate boundary plates diverge and create land as magma rises through
either fissures or splits, the type of crust at a constructive plate boundary is always oceanic,
and there is no subduction as the plate material is the same density. Whereas at a destructive
plate boundary plates converge and the dense oceanic crust subducts under the less dense
continental crust, An example of a constructive plate margin is the mid Atlantic ridge which is
the margin where the North American plate and the Eurasian plate diverge. An example of a
destructive plate boundary is the Peru-Chile trench where the oceanic Nazca plate subducts
under the South American plate.
- There are three types of plate boundary : Constructive, Destructive and Conservative
boundaries, Earthquakes happen at all three, whereas Volcanoes can only happen in 2 as
there is no subduction in a conservative boundary.
2
Geography revision
Naturals Hazards
- A natural hazard is an event which has a significant social impact.examples of natural
hazards are Earthquakes, landslides and flooding.They can be categorised as
atmospheric hazards , flooding and geological hazards
- A natural event becomes a natural hazard when the lives of people or property are in
danger.
- More people will be affected by flooding than any other hazard groups as lots of
densely populated cities lie on the banks of major rivers , like Dhaka which is
surrounded by many tributaries of the Ganges river in Bangladesh.Dhaka has a
population density of 45000 people/km2
- the main risk factors associated with an increase in the amount of natural hazards per
year are urbanisation ,as more people migrate into cities. with an increased population
density many large cities are in danger of a catastrophic natural hazard. Global
warming induced climate change brings rising sea levels and a runway sea and land
global temperature median give typhoons like Haiyan in 2013 more wind velocity and
tsunamis like the 2011 Japanese tsunami higher waves which creates havoc for those
living in coastal areas. Farming also drives many people to floodplains of rivers were
to river brings up nutrient rich sediment and silt from the river bed which gives farmers
better crop yields. In flat low lying areas this is deadly like the ganges delta and
floodplain in Bangladesh. In LEDC’s building companies use cheap materials instead
of actual materials due to lack of subsidy from governments to complete substandard,
haphazard infrastructure which are waiting to be exposed by a minor natural hazard
like in Taiwan where a 17 storey building collapsed after a 6.4 magnitude earthquake
leaving empty vegetable oil cans visible in the foundations. All these factor intertwine
to create a good chance for massive catastrophe in large cities as urbanisation drives
people to large cities to look for employment opportunities. mass poverty forces
building companies to use substandard materials to complete ‘relief’ infrastructure to
house as many people as possible and farming draws people out tO coastal areas
where land is plentiful and fertile but climate change brings rising sea levels which can
often devastate huge swaths of coastal land.
- When answering a photo question look for evidence of impacts and think
about what people there do for livelihood.and the economic state of the
1
, Sunday, 1 January 2017
country being observed.As well as how the disaster has affected them
socially and environmentally and whether any of these points link together
Tectonic Hazards
- A tectonic plate is a section of the Earths crust, there are two types of tectonic plates; the
dense - thin oceanic crust (basalt) , and the less dense - thicker continental crust (granite)
- Plates move due to convection currents deep inside the mantle where liquid magma drags
plates towards each other , or away from each other .
- Volcanoes are a type of natural hazard produced when magma from deep inside the earth
rises, upon reaching the surface the magma cools and solidifies forming huge composite
volcanoes, these volcanoes are produced at destructive plates boundaries where magma is
more viscous and has a higher silica content as well as more rock minerals and water vapour
dissolved in it. this means on breaching the crust the magma doesn't flow far and stacks in a
short radius(andes range).however shield volcanoes are produced at constructive boundaries
as the magma has a low viscosity and a low silica and mineral content, this means on
breaching the oceanic trench the lava flows relatively long distances and forms gently sloping
and flat shield volcanoes, like (Mt Kilauea)
- Earthquakes are a type of natural hazard and occur at plate boundaries when plates slip and
discharge huge amounts of tension built up of over hundreds of years.
- the global distribution of Earthquakes are mainly concentrated on plate boundaries, around
90% of earthquakes happen on or around the Pacific ring of fire; like on the San Andreas fault
on the American west coast. Very few earthquakes defy this generalisation, but one exception
are the Earthquakes produced in the Himalayas which is a collision zone. All recorded
earthquakes follow a linear pattern.An earthquake zone which follows all of the general trend s
are the earthquakes produced in the ocean and land surrounding or in Japan.
- At a constructive plate boundary plates diverge and create land as magma rises through
either fissures or splits, the type of crust at a constructive plate boundary is always oceanic,
and there is no subduction as the plate material is the same density. Whereas at a destructive
plate boundary plates converge and the dense oceanic crust subducts under the less dense
continental crust, An example of a constructive plate margin is the mid Atlantic ridge which is
the margin where the North American plate and the Eurasian plate diverge. An example of a
destructive plate boundary is the Peru-Chile trench where the oceanic Nazca plate subducts
under the South American plate.
- There are three types of plate boundary : Constructive, Destructive and Conservative
boundaries, Earthquakes happen at all three, whereas Volcanoes can only happen in 2 as
there is no subduction in a conservative boundary.
2
