Physical Geography

Physical Geography

1. Restless Earth

   • How do convection currents cause plate movement
     • 1. The core heats the molton rock in the mantle which creates a convection current.
       • 2. The heated rock rises to the surface.
         • 3. At the surface convection currents move the tectonic plates in the crust.
           • 4.Molton rock cools and flows back to the core.
   • 3 main plate boundaries
     • Collison Plate boundries - E.g: Indo Australian and Eurasion plates  - two continental plates collide and the two plates buckle - Many Earthquakes
     • Destructive
       • when 2 plates colilde one flows under the other (subduction)
       • e.g. Nazca Plate and South American Plate
       • Earthquakes and volcanoes occour
     • constructive
       • Rising convection currents pull apart
       • e.g. Eurasion and North American Plate
       • forming volcanic ridges e.g. Mid-Atlantic RIdge
     • conservative
       • Two plates slide past one another
       • e.g San Andreas Fault California
       • Earthquakes
   • Volcanic and earthquake hazards
     • Earthquake in Kashimer 2005
       • 75 000 dead
       • 2.8 million homeless
       • 75 000 injured
       • property damage $440 million
     • Earthquake in California, 1989
       • up too 12 000 homeless
       • 3757 injured
       • property damage $10 million
       • 63 dead
   • volcanoes
     • shield volcanoes
       • found on constructive plate boundaries
       • formed by long thin,runny lava which flows a long way before it solidifies
       • gentle sloping sides and a wide base
       • contains baslaltic magma which is very hot with low silica and gas content
       • Erupts frequently but not violently
     • composite volcanoes
       • found on destructive plate boundraies
       • formed by eruptions of viscous sticky lava and ash that don't flow far
       • have steep slopping sides and narrow base
       • made up layers of thick lava and ash
       • contains andesitic magma which is less hot but contains lots of silica and gas
       • erupts frequently but not violently includes pyroclastic flow
   • Managing earthquake and volcanic hazards
     • they are very difficult to predict
       • - when will they be  - where will it be exactly - how big? - What other impacts will there be - how many people live there - can we evacuate the people
     • what can help predict earthquakes
       • - animals and birds fly away - increase in gas emmisions - increase in soil temperature - volcano swelling - increase in small earthquakes - water ponds getting warmer
     • lots needed after an earthquake e.g. volunteers, clean water
       • - trained volunteers to help clear up debris, injured and dead people - clean water to prevent spread of disease - food as often roads, farms, shops and towns have been effected - radio communication because phones will often not work - medical people to care for the injured - a plan to evacuate the area if needed
   • Case Study: Mount Pinatubo Volcano 1991
     • Social Effects
       • 58 000 people were evacuate from a 30km radius of the volcano
       • 874 deaths in total
       • 300 killed from collapsing roofs
       • 100 killed by layhars
       • 1.2 million lost their homes
       • people round the volcano had to migrate to shanty towns in manila
     • Economic Effects
       • houses & bridges destroyed and needed replacing
       • Manila airport had to be closed
       • 1991 harvest destroyed and 650 000 people lost their jobs
       • farmland destroyed by falling ash & pumice unusable for years
       • Heavy rainfalll from Typhoon Yunga causes buildings to collapse
     • Enviromental Effects
       • Fast flowing volcanic mudflow (Lahars) cause servere river bank erosion undercut bridges etc.
       • Volcanic ash blown in all directions over hundreds of kms, smothering fields and buildings
       • Global cooling caused by ash in the atmosphere of 0.5c
     • Where?
       • Island of Luzon in the Phillipines
       • SE Asia at the destructive plate boundry between the Eurasion & Philippine Plates
     • Why?
       • Result of Oceanic Philipine plate being subducted under the lighter continental Eurasion plate
     • What?
       • Composite Volcano exploded in June 1991 creating Lahars & massive ash & gas cloud
     • Managing the hazard
       • Prevention
         • 75 000 people evacuated up to a 30km radius
         • US Air Force helicopters helped evacuation
         • Alert Systems put in place to warn of eruption
         • Government Shelters
         • Strategies for long term aid and disease control during evacutions
       • Prediction
         • 75 000 people were evacuated due to accurate predictions
         • Set up a permanent monitoring points or use satellite images to look at volcano site for changes in land surfaces
         • The US Geological Service helped to predict the disaster
         • No monitoring till April when seisometers were put into place
       • Prepatation
         • Evacuation camps built for refugees
         • Warning sign like gas and steam looked for
         • Long & short term aid organised especially from the Red Cross and the US
         • Storage of medical supplies of food and water in preparation for disaster

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