IGCSE Physical Geography

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IGCSE Physical Geography

• Topic Revision
• Part 2

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Ecosystems

• An ecosystem is a natural system in which life
  cycles of plants and animals are closely linked
  to each other and to the non-living environment
  (water, air, rocks soils).
• Ecosystems can vary in size from Global to Micro.
• Ecosystems are sustained by the energy flow
  through it starting with plants converting the
  suns energy (photosynthesis) then through the
  food chains trophic levels.

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Ecosystem Nutrient Cycle
Dying organisms
(living matter)
(leaf fall)
Decomposition
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Ecosystem Interactions Diagram

• Relief
• Climate Soils
• Vegetation

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Biomes (Global Ecosystems)

• 4 main biome climates
• Equatorial
• (High constant temperatures, High convectional
  rainfall)
• Tropical Continental
• (Seasonal hot wet cooler dry)
• Hot Desert
• (High annual temp temp range, high daily temp
  range, very low rainfall)
• Mediterranean
• (moderate annual temp, temp range rainfall.
• Seasonal hot dry summers, warm wet winters)

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• Biomes - Vegetation
• Equatorial
• (Luxuriant rainforests with continuous growing
  seasons.
• thin fertile soil layer)
• Tropical Continental
• (diverse vegetation from rainforest to savannah
  xerophytic to desert)
• Hot Desert
• (sparse vegetation drought resistant)
• Mediterranean
• (Originally woodland scrub now deforested for
  agricultural development)

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Plate Tectonics

• The theory that the earths crust is made up of
  plates that move (continental drift) due to
  convection currents in the earths mantle.
• Where plates meet is called a plate margin.
• These margins can be
• Destructive (plates converging subduction or
  folding/faulting) Violent EQs Volcanoes
• Constructive (plates move apart oceanic ridges)
  Gentle Volcanoes weak EQs
• Conservative (plates move past each other)
  Frequent, sometimes violent EQs

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Effects of Plate Tectonics

• Plate Tectonics is the cause of most Earthquakes
  and Volcanoes.
• There is a clear pattern between the distribution
  of EQs / volcanoes and plate margins.
• The formation of many of the worlds landforms
  are associated with tectonics e.g. the Himalayas,
  the Andes, The Pacific Ring of Fire .. etc.

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Volcanoes

• Volcanoes can be classified several ways
• By activity (active, dormant, extinct)
• Shape/Composition (cone shaped ash composite,
  shield)
• Cone shaped thick slow moving lava gtgt steep
  sided
• Shield runny fast moving lava (basaltic)gtgt
  gentle slope
• Hazards from Volcanoes
• Lava flows, Lahars, Dust Ash clouds, Nuee
  ardentes.
• Benefits from Volcanoes
• Fertile soil, geothermal energy, rocks for
  building, tourism

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Earthquakes

• An earthquake is the vibration of the Earths
  crust caused by shock waves travelling outwards
  from sudden movement deep within the crust.
• The source is the focus which is directly below
  the epicentre on the surface.
• Shockwaves are measured on a seismograph which
  measures the magnitude on the Richter scale.
• Impacts include Primary (deaths/injury, building
  collapse, damage to infrastructure) Secondary
  (fire/flood, lack of services, disease, homeless,
  unemployment, psychological)
• Factors affecting impacts strength depth,
  distance from epicentre, geology, population
  density (urbanisation), time of day or season,
  remoteness, country wealth/location.

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Earthquake Prediction Preparation

• It is not possible to predict EQs with any
  accuracy but there are some signs (increased
  tremors, unusual animal behaviour, gas emissions
  from ground).
• However cities in high risk areas can prepare by
• Land use planning building codes
• Improved building design (EQ resistant buildings)
• Emergency plans (Civil Defense) and evacuation
  procedures.
• Public education of how to prepare and what to do
  during and after an earthquake.

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Case Studies

• Volcanoes
• Mt St Helens (1980)
• Earthquakes
• Kobe, Japan (1995)