section A: the challenges of natural hazards Flashcards
-natural hazards -tectonic hazards -weather hazard -climate changes
What is a natural hazard?
Natural hazards= a natural environmental event that could potentially impact a person
What’s a hazard risk?
Hazard risks=the chance of being affected by a natural hazard
What’s an example of hazard risk?
Those living near the sea are at risk of flooding caused by tropical storms
What factors affect risk?
Urbanisation-densely populated urban areas concentrate this at risk
Poverty- shortage of housing leads to building on risky ground
Farming-the attraction of fertile silt on floodplains puts people at risk
Climate change-global warming raises sea levels and generates more extreme weather
How did plate tectonic theory develop?
Alfred Wegener suggested in 1912 that the continents were once joined together and then gradually floated apart
What was the evidence for plate tectonic theory?
-Fossils found in parts of the continent
-fit together like a puzzle
What are the two tectonic plates and describe them?
Continental-less dense, thicker and older crust
Oceanic-denser, thinner and recently formed crust
What are the plate margins called were plates separate?
Constructive-plates pull apart
Destructive-oceanic plate subduct’s continental plate
Conservative-plates move in opposite directions and get stuck
What makes tectonic plates move?
Conventional currents
Describe how conventional currents works
Heat driven cycles that can move tectonic plates onto their side and gravitational sliding causes the tectonic plate to come back down to the ground.
What happens at ridge push?
Ridge push is the result of gravitational forces acting on the raised oceanic lithosphere around mid-ocean ridges, causing it to slide down the similarly raised but weaker asthenosphere and push on lithospheric material farther from the ridges
What happens at slab pull?
This is similar to a destructive plate boundary where the oceanic crust subduct’s the continual crust
Gravitational sliding:
1)ridge push at divergent margins is caused by rising magma pushing part of the plate on its side
2)slab pull brings the tectonic plate downwards due to gravitational sliding
At what two plate boundaries can ridge push and slab pull happen?
constructive (is ridge push) and destructive (slab pull)
Constructive margin:
-when two tectonic plates pull apart usually continental plates
-magma is heated becomes less dense causing it to rise
-as it reaches the top it breaks the crust with little force and causes a mild earthquake
-the magma that erupts out of the newly created gap causes a flat shield volcano because of its low viscosity and creates flat shield volcanoes
Destructive plate boundary:
-the oceanic plate subduct’s the less dense continental crust
-the continental crust remains but starts to crack
-the oceanic plate starts to melt due to friction and causes hit magma that rises and tries to fit through the cracks of the continental plate
-the magma erupts with force out through the cracks creating a strong earthquake and composite volcanoes
Conservative plate boundary:
-two plates move past each other in opposite directions
-they get stuck due to friction
-as they are still trying to move it causes pressure
-this pressure is then realised as the plate slips and releases huge amounts of energy called seismic waves which causes the ground to shake
Where do only earthquakes form?
Conservative
Primary effect? Example?
Immediate impact- killed, made homeless , a building collapsed
Secondary effect? Example?
Long term impact- diseases , lack of natural resources
Primary response:
Stop and search for survivors
Receive medical treatment from other countries
Secondary response:
Practise drills
Why do people live at risk from tectonic hazards?
Poor people have no choice
Not seen as a great threat
Volcanoes can bring wealth from tourists and people do it for the money
Monitoring volcanoes:
Monitoring earthquakes:
Scientists use science equipment such as a seismometer to detect and record micro quakes
same goes for volcanoes scientist use seismometers
Prediction volcanoes:
Prediction earthquakes:
Volcanoes-monitoring is now allowing accurate predictions and effective evacuations even though they still are not 100 precent sure
Earthquakes- accurate predictions are impossible due to lack of clear warning signs but historical records help
Protection volcanoes:
Protection earthquakes:
Volcanoes - earth embankments have been used to successfully diverts lava flow
Earthquakes- earthquake proof buildings
Planning volcanoes:
Planning earthquakes:
Volcanoes- hazard mapping is used to identify areas to control development in at risk areas
Earthquakes- shakemaps are used to identify lower risk areas to locate high value buildings
What’s global atmospheric circulation?
Atmospheric circulation involves a number of interconnected circular air movements called cells
Describe atmospheric circulation:
-sinking cold air creates high pressure and rising warm air creates low pressure
-surface winds move from high to low pressure transferring heat and moisture from one area to another
-the winds curve due to the earths rotation of the earth causes relative changes in the position of the overhead sun
How does global circulation affect the worlds weather?
Cloudy and wet where we live because 50-60 N is close to where cold polar air from the north meets warm subtropical air from the south.The surface winds from the south west usually brings warm and wet weather because riding air cools and condenses
CHECK MORE IN TEXT BOOK PAGE 24
What are tropical storms?
They are huge storms called hurricanes, cyclones and typhoons in different parts of the world
How do they from?
Most form 5-15 North and south of the equator in autumn and summer where ocean temperatures are highest(above 27 degrees).The spinning (coriolis) effect of the earths rotation being very high.
Intense heat and humidity make air unstable ,causing it to rise rapidly
What is tropical storms formation affected by?
Global atmospheric circulation
How does global atmospheric circulation affect tropical storms?
-unstable rising air in the equations, regions(where the two Hadley cells converge) encourages air to rise ,condense and from storm clouds
-wind blows from high pressure belts (sub-tropical) to low (equatorial).These trade winds are responsible for the predominantly eats-west storm paths
The structure and features of a tropical storm:
Winter-no
-the centre of the eye -a column of rapidly sinking cool air where conditions are relatively calm and there are no clouds
-at the outer edge of the eye is the eye wall-the most severe conditions with very strong winds including tornadoes and torrential rainfall
-cumulonimbus clouds swirling around beyond the eye wall bring additional bands of rain
How are tropical storms triggered?
The upward movement of evaporated air and moisture
When to tropical storms stop?
When they reach land
