Natural Hazards Flashcards
What is a natural hazard
Natural hazards are sudden severe events which make the natural environment difficult to manage. They disrupt life and have huge social and economic impacts. They mainly fall into 3 groups: Atmospheric, geological and flooding
What is a Hazard risk
hazard risk means the chance of being affected by a natural hazard. For example those living near the sea at risk of flooding caused by tropical storms of tsunami. People live in risky areas because they:
Accept the risk after weighing up advantages and disadvantages
have little choice of where to live
Where do most earthquakes occur
Most occur at the margins of slow moving tectonic plates
What are the 2 types of plates
Oceanic and continental
Why do tectonic plates move
Because of convection currents
Distribution of volcanoes
Volcanoes occur across plate margins but some occur at hot spots where the crust it thin and magma breaks through
Why do people live at tectonic hazards
.Poor people have no choice
.Earthquakes and volcanic eruptions can be seen as rare so they’re not seen as a great threat
.Earthquake resistant buildings reduce risk
.Effective monitoring’s of earthquakes and tsunamis allow evacuation warnings to be given
.Plate margins often coincide with favorable areas for settlement and trade
.Some people have no knowledge of the risks
.Volcanoes can bring benefits such as fertile soil
.Earthquake fault lines allow for water to reach the surface
E.g San Fran is at risk of earthquakes but there is a good tech industry there
How can risks from Tectonic hazards be reduced
.Monitoring
.Prediction
.Planning
.Protection
What is global atmospheric circulation
Atmospheric circulation is a number of interconnected circular air movements called cells, these include:
.Sinking air which creates high pressure and rising air which creates low pressure
.Surface winds which move from high to low pressure, transferring heat and moisture from one area to another
.These winds curve due to the Earth’s rotation and change seasonally as the tilt and rotation of the Earth causes relative changes to the position of the overhead sun
What is a tropical storm
Tropical storms have been called huge cyclones and typhoons in different parts of the world. They form 5-15 degrees North and South of the equator in Summer and Autumn where where:
.Ocean temperatures are highest
.The spinning (coriolis) effect of Earth’s rotation is very high
.Intense heat and humidity makes the air unstable
How do tropical storms form
Rising air draws evaporated water vapour
up from the ocean surface which cools and
condenses to form towering thunderstorm
clouds.
The condensing releases heat which powers
the storm and draws up more water vapour.
• Multiple thunderstorms join to form a giant
rotating storm.
Coriolis forces spin the storm at over 120 km/h
(75 mph) creating a vast cloud spiral with a
central, calm eye of rapidly descending air.
• Prevailing winds drift the storm over the ocean
surface like a spinning top, gathering strength
as it picks up more and more heat energy.
• On reaching land the energy supply (evaporated
water) is cut off and the storm will weaken.
How does global circulation affect the world’s weather
• Cloudy and wet in the UK because 60° north
is close to where cold polar air from the north
meets warm subtropical air from the south. These
surface winds from the south-west usually bring
warm and wet weather, because rising air cools
and condenses forming clouds and rain.
• Hot and dry in the desert because most deserts
are found at about 30° north and south where
sinking air means high pressure, little rain, hot
daytime temperatures and very cold nights.
• Hot and sweaty at the Equator because low
pressure marks where the sun is directly
overhead. Hot, humid air rises, cools and
condenses, causing heavy rain - hence the
tropical rainforests.
The structure of tropical storm
Beyond the eye there are further banks of clouds and thunderstorms and occasionally tornadoes. There will also be strong gusty winds with heavy rain.
One either side of the eye is a tall bank of cloud called the eye wall. Here there are strong winds in excess of 120 km/h. Heavy rain, thunder and lightning
.The central eye can be seen clearly here. This is a small area where relatively cold air sinks towards the ground and warms up. There are no clouds here and the conditions are calm.
What are the UK’s weather hazards
Thunderstorms, Prolonged rainfall, drought, Heavy snow, Strong winds
How can monitoring help a country
Storms cannot be prevented but they can be monitored and their tracks can be predicted. This allows for warnings to be made and preparations to take place.
How can protection help a country
Methods of protection often involve anticipation in design. They can involve buildings such as cyclone shelters which are ready to use in case of a natural hazards and can be further used as places of teaching, community centers or other uses.
