Geography Unit 2

Geography Unit 2

1. Structure of the Earth

   • Core-Iron and nickel
     • Inner core-Solid,at centre of the Earth: 5500*c
     • Outer core- Semi-molten
   • Mantle-Silicate rocks, in rich iron and magnesium,semi molten:2000*c.
     • High temps cause convection currents.
   • Crust
     • Oceanic: SIMA, mainy basalt, 6-10km thick, 1200*c at deepest point, density:3g cm -3
     • Continental: SIAL, mainlly granite, up to 70km thick, density:2.7g-3
   • Convection currents
     • The oceanic and continental plates float on top of the mantle due to convection currents
     • The liquid in the mantle gets heated by the core.
     • The warm material has more energy so it rises towards the surface.
     • when it eventually cools down the material will have less energy so will sink
     • This creates a up down motion that carries on in circles
   • The theory of Plate tectonics
     • The Earths crust is broken up into pieces called plates
     • Convection currents inside the mantle move the plates
     • The movement of the plates is called plate tectonics
     • Constructive plates: Divergent
     • Destructive plates: Subduction zone- Convergent
     • Destructive: Collision Zone-Plates convergent
     • Conservative-Plates move past each other-Transform

2. Earthquakes

   • An earthquake is a series of vibrations and shock waves which are initiated by volcanic eruptions or movement along plate boundaries
   • Focus-The point where the pressure is released- the origin of the quake
   • Epicentre-the point on the Earth's surface immediately above the focus.
   • Seismic Waves- Shockwaves that spread out from the focus. They act like ripples on a pond the further they travel the weaker they get
   • Earthquakes are measured using a seismometer and create a trace called a seismograph
   • The intensity of the earthquake is measure on the richter scale
   • Haiti eathquake 12th January 2010
     • 7.0 on richter scale
     • Focus 12km below surface
     • Caribbean plate and North American Plate
     • 72.1% of the population live on £2 a day
     • Most of the population live in tightly packed shantytowns and badly constructed buildings
     • 230,000 people died
     • Primary effects
       • Water pipes burst
       • Buildings damaged
       • Airport at Port-au-Prince lost its control tower
       • Roads damaged and bridges collapsed
     • Secondary effects
       • Food supplies ran low
       • Mass graves to bury dead to prevent disease
       • Aid aircraft blocked the airport for hours whilst being unloaded , as well as a shortage of jet fuel
       • Difficulty distributing supplies around the island due to damages to roads and bridges
       • Shortage of medical supplies and expertise
       • 1 in every 16,588 were rescued
       • 1 million people are homeless and live in temporary tented settlements
     • Management
       • 17 search and rescue teams looked for survivors in the rubble
       • Helicopters were loaned to make the distribution of aid easier.
       • US navy sent aircraft carriers to the area

3. Vocanoes

   • A volcano is an opening, or a rupture, in a planets surface o crust, which allows hot, molten rock, ash and gases to escape from below the surface
   • A volcano can be one of three things:
     • Active-a volcano that has erupted recently
     • Dormant- a volcano that has erupted in the last 2000 years
     • Extinct-a volcano that hasn't erupted for many thousands or millions of years
   • Viscosity- the thickness of lava, which directly affects how far the lava can travel
   • Mount Pinatubo, Philippines 12th-15th June 1991
     • Composite volcano
     • An explosive eruption
     • Primary effects
       • The ash clouds rose 22 miles into the air
       • Volcanic ash and pumice pebbles blanketed the countryside
       • Pyroclastic flows roared down mountain sides filling valleys with fresh volcanic deposits as much as 660ft thick
       • Lava bombs the size of ping pong balls fell in Subic bay
       • The sky turned dark
     • Secondary effects
       • 200,000 people who were evacuated from the lowlands surrounding Pinatubo before and during the eruptions have returned home
       • Continuous threats from mudflows that have already buried numerous towns, villages and fields
       • Weight of ash collapsed the roof of the Angeles city bus station
   • Types of Volcano
   • Eyjafjaffajokull, Iceland March-April 2010
     • The eruption began in march then entered a new explosive phase in April
     • Eurasion an North American Plate diverge at a constructive plate boundary
     • The volcano is located in South-west Iceland, it's near the sea, and it covers around 40sq miles.It's 1666 metres tall
     • Primary Effects
       • Air space was closed in areas all over the world due to ash and safety fears
       • Large amounts of ash covered towns
       • Farmers to the east were affected massively by the ash, Their livestock either had to be sent to the slaughter house or they tried desperately to move them
       • The ash made the roads very dusty and it was like driving on a dirt road in Africa
     • Secondary Effects
       • 120,000-150,000 Brits were left stranded abroad, including teachers and pupils on there easter holidays
       • 100,000 flights were cancelled
       • It cost tour operators and the aviation industry up to 2.5bn euros
       • It cost London more than £100 million in tourist spending for six days of flight ban
       • In Iceland the was a big impact on the tourist industry which made u 40% of their GDP

4. Tropical Storms

   • Formation of Tropical storms
     • Most form 10* to 30* North and South of the Equator but rarely within 5*
     • Sea temperature must be over 27*C
     • 1. Several thunderstorms drift over warm seas
     • 2.The warm air from the sea surface and the thunderstorms combine and warm air starts to rise
     • 3.More warm air rises and, due to the Earths rotation, starts to move in a spiral. It cools down and condenses, forming clouds, releasing much energy
     • 4.The air starts to rise faster and the cooler air is sucked downwards. Wind speed begins to incease
     • 5.The tropical storm moves over the ocean, picking up warm, moist air. Wind speeds reach more than 120km/h as more cold airis drawn into the eye
     • 6.Storms track westward and eventully make landfall. As they cross the land, they lose the source of their energy and start to reduce in strength
   • Differnet regions called tropical storms different things:
     • North America=Hurrcanes
     • Indian Ocean=Tropical Cyclone
     • South East Asia=Typhoons
   • Tropical Storms are measured on th Saffir-Simpson Scale
   • They are large low pressure systems (extreme depressions)
   • Eye-the calm, clear area in the centre of the tropical storm
   • Track-the path taken by a tropical storm
   • Hurrican Katrina 29th August 2005
     • Several key levees were breached ,causing flood water to pour into the low lying city
     • By August 31st an estimated 80% of New Orleans was underwater
     • New Orleans lies below sea level
     • The levees were only designed to deal with a category 3 hurricane, Katrina was a category 4
     • Most houses were flooded to the ceiling leaving hundreds homeless
     • Many took refuge in the city's Superdome(9000) but without proper sanitation or supplies , conditions in the overheated stadium became increasingly unbearable
     • Widespread looting and violence
     • Katrina caused smaller tornadoes to spawn causing damage in other states including Georgia

5. Wildfires

   • Climatic features needed for a wildfire
     • Hot, dry weather
     • Strong winds can fan the flames
     • Drought
     • South facing slopes, have dryer vegetation
     • Steep slopes means fire spreads quickly as it comes into contact with vegetation upslope
   • Natural Causes
     • Lightning strikes
     • Spontaneous heating-where a material becomes heated to the point where it will catch fire without a spark present
     • Volcanic eruption
   • Human causes
     • Accidents- Eg: Campfire not being put out properly
     • Broken bottles magnify heat
     • slash and burn- used by farmers to clear land to grow crops which can get out of hand
     • Arson
     • Sparks from machinery
     • Military exercises
     • Household chimneys
     • Barbacues
   • Fuel sources
     • Forest fuels-Consists of ground,surface and aerial materials
     • Ground fuels-Lie below the Earths surface Eg:roots
     • Surface fuels-Twigs, grass, wood, tree needles
     • Aerial fuels-Tree crowns, branches and hanging mosses
   • Fire triangle
   • Black Saturday, Australia, 7th February 2009
     • Australia was experiencing one of its worst heat waves with temperature u to 47 degrees
     • Rainfall totals were below average
     • 173 people died
     • 113 died trying to defend their homes from the flames-the 'Stay and defend@ approach
     • The bushfires destroyed 2,000 properties in 78 communities
     • in Kingslake, a dozen people died and 550 homes were to the ground
     • Survivors complain that they had little or no warning about the flames racing towards them
     • 500 injured
     • Aircraft water bombed the flames
     • Tens of thousands of firefighters were battling the blazes
     • One man was charged with lighting one of the many fires that started the wildfire

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