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Year 9 Geography Notes- HAZARDOUS ENVIRONMENTS !

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Hazards!

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)What is the difference between a natural hazard and a natural disaster?!
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•The difference between a natural hazard and a natural disaster:!
-Natural hazards are the event itself while a natural disaster is the affect of that
event on people (when over 10 people are killed by a hazard it it known as a natural
disaster)!

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•Two ways by which an earthquake might cause injuries or deaths:!
-They cause sudden ground shakings- building can collapse and injure people
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It can also
asphyxiate humans and animals
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•Geological (Tectonic) hazards= volcanic eruptions and earthquakes!
•Climatic Hazard= tropical storms!

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Global Distribution of Earthquakes and Volcanic Eruptions!
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It is the surface of the world
we live on and is 8km-70km thick, depending on whether it is oceanic or continental
crust
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)What are tectonic plates?!
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•Tectonic plates make up the crust and are the rigid blocks that move across the
globe
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They can also be
either oceanic or continental
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)What causes the plates to move?!
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-move due to heated magma rising from the mantle!
-it reaches the crust and spreads out and drags along the crust!
-creates friction between the magma and the crust which pulls the crust in its
direction, causing the plates to move
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•A plate margin!
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•Table of different plate margins:!

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- Neither can sink or be destroyed!
- Rocks between them are forced
upwards, forming fold mountains
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•Constructive!
-Convection currents in the mantle
cause the tectonic plates to move
apart from each other
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-Expect Volcanic eruptions and
earthquakes here
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-The oceanic crust is forced
underneath !
because it is denser, this movement
downwards is called subduction
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-great pressure in the mantle forces
magma towards the surface!

-This leads to infrequent but very powerful volcanic eruptions !
-Also Earthquakes can occur due to the friction between the two plates
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-This movement is not smooth as
the plates become jammed
against each other by friction!
-This pressure of friction is built up
until it becomes too great and
released in a sudden, violent
jolting movement (earthquake)!
-No volcanic eruptions take place
here
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)What is an earthquake?!
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•An earthquakes is:!
-a sudden or violent movement within the Earth’s crust!
-followed by a series of shocks!

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-When two plates move side to side they will cause friction !
-They will build up pressure until the two plates slip and all that energy/pressure is
released in the form of seismic energy!
-This is what an earthquake is!
-Will happen more often at a plate margin since it is a weak spot and so it will allow
more earthquakes to occur
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The closer something is to the epicentre, the more damage will happen to it
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Primary effects: Direct impacts!
Secondary effects:Subsequent/Knock-on impacts of the earthquakes
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-Death is a secondary effect since an event occurs (buildings collapsing) which
leads to the death of people
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-Richter Scale!
-Mercalli Scale!

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•Impossible to prevent an earthquake!
•Preparation and Protection:!
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Federal Emergency Management Agency (FEMA) earthquake program has
the following objectives:!
*To promote understanding of earthquakes and their effects!
*To work better to identify earthquake risk!
*To improve earthquake-resistant design and construction techniques!
*To encourage the use of earthquake-safe policies and planning practises !
•Hazard Resistant Structures:!

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Torre Mayor, Mexico City!
-Deep foundations gives more support for the building to remain stable!
-In these deep foundations are shock absorbers which absorb the rolling and
shaking from an EQ instead of the building!

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This strengthens the frame work
of the building!
-Big triangle frames across the building because triangles are the strongest shape
and also it allows the building to twist (torsionally)!
-Because of this there are no weak points
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Base Isolation!
-The foundations of the building are attached to
rubber bearings
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-Allows the building to move as one and limit the
damage !
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the base moves in isolation to the building
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•Emergency Services:!
-Needs careful organisation and planning!
-Civilians must be given first-aid training!
•Land-use planning:!
-The most hazardous areas in the event of an earthquake can be identified and
regulated!
-Lessens amount of deaths!
•Insurance and Aid:!
-In HICs, people are urged to take out insurance to cover their losses- can be very
expensive for some people!
-Most aid to LICs has been emergency aid e
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providing medical services, water
purification etc
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7 magnitude on the Richter scale!
-Ground shook for 15 seconds!
•Location:!
-On a previously undiscovered fault (Northridge or Pico blind thrust fault)!
-Focus was 18
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)Discuss the factors which affect the death toll in an earthquake?!
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•Preparation of EQ:!
-Quality of heath care and emergency services!
-How educated people are about earthquakes
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•Secondary effects:!
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Tsunamis, fires, floods!
•Time of day/year:!
-Night time= dark and people are asleep, because of how dark it is it may cause
injuries and deaths!
-Day time= people congregate for work in the day and if the building collapses, that
means there will be more deaths
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-Winter is the worst season to have an earthquake as it is cold and pipes can break
easily
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)How are volcanoes formed and describe volcanoes at plate boundaries:!
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-Magma is forced up through the crust and once it is above the surface it is called
lava!
-Happens at destructive plate boundaries, the eruptions here are less frequent but
often very explosive
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The lava here is runny, forming a wide volcano with more gentle slopes
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•BASIC Lava:!
-Low silica content!
-fluid/runny (travels long distance)!
-emitted in non-violent eruptions!

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-a flow of melted snow, volcanic ash and water (sometimes from a crater lake)!
-flows in river valleys at 100mph!
-destroy everything (also floods banks)!

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-Dense cloud of hot ash, rocks and steam !
-flow down the volcano at 200mph usually in river valleys!
-Burns and destroys anything in its way!
-A major hazard as since it is dense it is close to the ground so it can injure people
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Research is
currently being conducted to see if we can use shock waves produced by magma
approaching the surface as a way of predicting
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•Can divert lava flow by:!
-digging trenches!
-artificial barriers, also protect against lahars!

TROPICAL STORMS!

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-They bring torrential rainfall and very strong winds to tropical regions!

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) In the Caribbean/Gulf of Mexico region, in which months of the year are
tropical storms most likely to happen and why?!

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-July to September (mid summer to early Autumn)!
-It is when the sea is at its warmest so the chance of low pressure being formed in
these areas is higher
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) What is the minimum temperature required in order for a tropical storm to
form?!

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-27 c!
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-Winds of a storm in the Northern Hemisphere rotate anti-clockwise!
-Winds of a storm in the Southern Hemisphere rotate clockwise!

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Describe how the rising air leads to clouds and rain
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-Low pressure is created when equatorial regions receive high levels of isolation!
-So the air is heated and rises
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-This equalisation is known as strong winds
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-So more air is needed to fill low pressure again!
-It builds up so higher wind speeds
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) Explain how the sinking air inside the eye helps to create the weather
conditions we would associate with the eye of a tropical storm
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-Air sinks from the top so it gets warmer on the way down (loses moisture to
evaporation) so no clouds will form
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) What is the name of the scale to classify the strength of tropical storms?!
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-The Saffir-Simpson Scale!
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-Given names by meteorologists in alphabetical lists with alternate male and female
names over a six year cycle
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-Helps to track and identify individual storms , especially if some are happening at
the same time
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) Describe four ways by which people may be injured or killed by tropical storms
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The shear force of the winds can collapse buildings, turn over cars and even lift
people
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Floods could destroy buildings and kill people as they flow viscously and could
drown people
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The high winds force the bulged sea over the coastal flood walls
to cause mini-tsunamis and a sea water flood
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•Impossible to prevent!
•Preparation and Protection:!
-Many things an individual can do to prepare for a tropical storm:!
*Supplies e
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drinking water, food, first aid kit, a radio etc
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-In addition, local and national governments may be able to help:!
*Issuing and overseeing evacuation orders!
*Educating the population about Tropical Storms!
*Building storm shelters!
*Building river/coastal defences to prevent flooding!

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CASE STUDY: HURRICANE MITCH AND HURRICANE FLOYD!
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Mitch

Floyd

Date

October 1998

September 1999

LIC or HIC?

LIC

HIC

Areas affected

Honduras( as well as
Nicaragua,EL Salvador,
Guatemala, Costa Rica, Belize
and Mexico)

North Carolina, Florida (as well as
Bahamas and NE USA

Strength

-5 while at sea with 180+mph
wind !
-1 when it made landfall with
80mph wind

-4 while at sea with 155mph in the
Bahamas!
-2 when it made landfall in N
Carolina with 105mph wind
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Mitch
Management

Floyd

-Proved difficult to predict!
-Poor evacuation due to poor
communication and transport!
-International aid was required in
the aftermath (rescue teams etc
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-The US government made $2 of
aid available to affected areas!
-Many people and businesses
had insurance to cover damage
costs
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) Why are the impacts of tropical storms usually more severe in LICs than HICs:!
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•Location/Latitude:!
-LICs are usually located in places where the conditions for development are lower!
-This means an LIC is more likely to be situated in a potential TS zone which would
devastate the country even more !
-Located in tropics, warm ocean temperature= strong TS!

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•Building Quality:!
-LICs are not as economically advanced as HICs!
-LICs do not have as much money to equip buildings with more advanced and
modern building materials which will be better to withstand TS
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-Higher chance of people losing their lives or getting injured!
-Also in some LICs e
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Honduras, people live on hills and so they can be hugely
effected by mudslides!

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•Tracking/Monitoring/Early Warning:!
-Tracking and monitoring systems are very expensive, so they can only be
possessed by HICs
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•Other:!
-Raised taxes to pay back debt!
-Citizens have no homes and forms of education (e
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schools) so development of
education and wellbeing would fall back as well
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) With reference to examples, discuss the reasons why people live in areas at
risk from volcanic eruptions
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It is a cheap and
renewable source of energy
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-More fertile soil- will provide good conditions for crop farming!
-Mining will provide jobs for locals and there swill be valuable minerals for the
industry
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) With reference to examples, discuss the reasons why people live in areas at
high risk from earthquakes:!
-Along plate edges, geothermal power is often a cheap and clean source of power
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Iceland!
-Many places like Japan get frequent, yet ineffective earthquakes, so their buildings
will be built to withstand them!
-Earthquakes are often close to the coast, but here the climate is good and fishing
and farming are easy!

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COASTAL FLOODING!
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CASE STUDY: NEW ORLEANS AND THE GULF COAST, USA!
•In 2005 Hurricane Katrina caused 80% of New Orleans to be underwater!
•Death toll of more than 1800!
•Since Hurricane Katrina, $14
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This included:!
-Massive new floodgates than can now be closed to block the canals if storm
surges threaten the city!
-Levees (huge artificial embankments) and flood walls are now higher and have
also been reinforced!
-A system of pumps operates constantly to prevent the city from flooding and are
now designed to continue operating through a storm!
•Further plans include:!
-Making sure that future information and warnings given to the public about storm
surges are more specific as storm surges can happen in areas a significant
distance away and so people do not know where they are
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This can be achieved by improving levees and
breakwaters (hard engineering) and restoration of features such as dunes,
beaches, marshes etc

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