Natural hazards Flashcards
what is a natural hazard
a natural event or process which causes loss of human life and/or damage to property
what is a hazard risk
the chance or probability of being affected by a natural event
factors affecting people’s risk from natural hazard
poverty
urbanisation
climate change
population growth
how does poverty increase the risk from a natural hazard
as people in poverty often make their homes in high risk areas and are made with cheaper materials as it is all they can afford
how does urbanisation increase the risk from a natural hazard
as there is not enough space in cities and they are very densely populated so when hazards (e.g earthquakes) occur, buildings can collapse which then causes lots of homes to be destroyed
how does climate change increase the risk from a natural hazard
as if the atmosphere gets hotter, there is an increased chance of hazards (e.g drought or famine) occurring and if it gets a lot wetter, the sea levels may rise and cause an increase in flooding and tsunamis
how does population growth increase the risk from a natural hazard
as more people will need homes and since there is less space available for housing, people may be forced to live in high risk areas
what are the types of natural hazard
hydrological events (flooding)
meteorological events (storm)
geophysical events (earthquakes)
climatological events (drought)
layers of the earth
crust
lithosphere
mantle
outer-core
inner-core
features of the crust
8-65km thick
made of basalt and granite
features of mantle
mesosphere (lower)
asthenosphere (upper)
1000-3700 degrees
2900km thick
84% of earth’s volume
made of olvine and peridotite
features of outer-core
made of iron and nickel
2300km thick
4400 degrees
liquid metal
features of inner-core
made of iron and nickel
solid metal
1220km thick
4.5 billion years old
6000 degrees
features of continental crust
lighter
less dense
made from granite
more buoyant
has land on it
25-75km thick
features of oceanic crust
heavier
denser
made from basalt
less buoyant
has sea on it
7-10km thick
what does a converging plate do
move together
what does a diverging plate do
move away
how does a convection current happen in the mantle
the heated magma in the mantle rises as it is less dense and as it rises, it cools and becomes denser again - causing it to sink and then heat up and so on
what is ridge push
mid ocean ridges are higher than the rest of the ocean floor so gravity causes the ridge to force the plate down
what is slab pull
tectonic plates are heavy so when a plate has started to sink, gravity and the fact that it is dense means that it will pull the rest of the oceanic crust down with it
where do volcanoes happen
there is a long line of volcanoes in the Pacific ocean
not many in Europe
few in the middle of the Pacific
plate boundaries
where do earthquakes occur
on tectonic plate boundaries
Asia (e.g Philippines)
some random places (e.g Australia)
what is a constructive plate margin
a gap appears between two tectonic plates and they pull away from each other due to ridge push and slab pull
molten magma rises to fill the gap and cools to create a solid rock and new crust
this creates a mid-ocean ridge of mountains as the magma is buoyant and pushes the crust upwards
sometimes this new rock fractures as it moves and causes a gentle, shallow earthquake close to the surface
sometimes lava escapes, usually as a gentle volcanic eruption causing shield volcanoes
how does a destructive plate margin occur
a plate with oceanic crust moves towards one with continental crust, which crumples to form fold mountains
the denser oceanic crust is subducted under the continental crust by slab pull - leaving a deep oceanic trench above
as the plates converge, pressure builds up and eventually the rocks fracture which causes strong earthquakes
deep in the mantle heat and pressure melt the subducted oceanic crust which rises as magma towards the surface
as the magma rises, it becomes viscous which causes violent volcanoes with steep sides
how does a conservative plate margin occur
two plates try to move side by side as either end of the plate is pulled or pushed
friction makes them stick so movement becomes increasingly difficult
pressure steadily builds up as the two plates try to move past each other
eventually, the pressure becomes too great and the rocks fracture, allowing the two plates to slip past each other
this causes strong earthquakes (but no volcanoes as there is no gap for magma to escape from)
factors that affect hazard risk
Population density
Urbanisation
Level of development
Human activities
Frequency of the hazard
Magnitude
Prediction
Planning
factors that affect risk of a natural hazard
Population density
Increased numbers of people in hazard prone areas
Urbanisation
Frequency
Magnitude
Level of development
Prediction
Planning
Human activities
why are more places prone to natural hazards
Lack of education
People do not know what do to in hazard event to stay safe
Lack of planning
Emergency services are not prepared
Low level of development
Leads to a lack of resources to deal with the hazard impacts
Lack of resources to rebuild
Location in areas which have more natural hazards
They don’t have the opportunity to recover
