Natural disasters Flashcards
definition of natural hazard
a natural event that poses a threat to people and the environment
what types of plates are there
Conservative Destructive (convergent) Constructive (divergent)
how are shield volcanoes formed and on what plate boundaries
on constructive (divergent) plate boundaries When the plates pull apart, magma rises from the mantle then pours out low viscosity lava which spreads flows easily, creating the dome shape over a period of multiple eruptions when they harden (layers only made from hardened lava)
how are composite volcanoes formed and on what plate boundaries
on destructive (convergent) plate boundaries When plates move towards each other the denser one will sink beneath the other. The plate is then melted, creating pressure to build up under the crust which eventually explodes through the crust. Its high viscosity lava builds up the volcano into the steep hill as It does not reach the bottom of the volcano before cooling (its layers are made from cooled lava and ash)
true or false, earthquakes occur at all 3 boundaries
True
how are earthquakes started at conservative plates
parallel plates shift at different speeds and different directions, friction is built up by this movement over many years. This releases a lot of energy which causes the ground to vibrate- an earthquake
what scale is used to measure magnitude of earthquakes
The Richter scale, the scale is logarithmic, and each level is 10x larger than the previous
what are primary and secondary effects to hazards+ examples
Primary effects: directly related to the hazard
- Destruction of infrastructure/ housing
- Death
Secondary effects: effects that are caused by primary effects
- Spread of diseases
- Poverty
- Homelessness
- Landslides
what are long term and short term responses
Short term: responses that take place immediately, or in a short time frame after the disaster
- search and rescue
- helping the injured
- aid workers from charity
- providing temporary shelter
Long term: responses that are often not immediate and take a long time to be carried out successfully
- Rebuilding infrastructure and housing
- rebuilding hospitals
what are physical defences
infrastructure that protects people or property from natural hazards
physical defences to ocean
- Sea walls
- Storm drains
- Houses built on higher ground/ stilts
- Reinforced infrastructure such as power lines
- Riprap
- Groynes
physical defences against earthquakes
- Rubber shock absorbers, at the base of buildings
- Steel frames that can sway during Earth movements
- Open areas outside of the buildings where people can assemble during an evacuation
Preparation for earthquakes
Many earthquake-prone countries hold drills in public buildings, such as schools, houses, etc in the event of an earthquake, this helps to reduce the impact of future earthquakes as fewer deaths will occur
Japan dedicates 1st September as ‘disaster protection day’
Can we predict earthquakes?
We can predict where they will occur, with seismometers
however we cannot predict when they will occur
what conditions are needed for a cyclone to occur
- water must be warm, around 27°C
- Require low-pressure systems so usually form between tropics of Cancer and Capricorn
- winds must be strong but not too strong in the beginning phases
- The cyclone will gain strength by going across the water, as this is its energy supply, it starts to lost energy as soon as it reaches land
- the way it travels depends on tide and prevailing winds
- Coriolis force
