Geography P1 OCR B

• Global circulation system


  The global circulation of air masses creates pressure belts and causes different weather conditions in different global locations. The air masses move in cells and these determine weather conditions.
• Air cells


  • Hadley Cells
  • Ferrel cells
  • Polar Cells
• Hadley Cells


  Hot air rises at the equator creating low pressure, the air descends at 23⁰ N+S creating low pressure
• Ferrel cells


  Air descends at 23⁰ N+S creating high pressure and rises at 60⁰ N+S creating low pressure there
• Polar Cells


  Air rises at 60⁰ N+S and descends at the Poles
• High pressure


  Dry, calm conditions
• Low pressure


  Wet, stormy conditions
• High pressure belts at 23⁰ N + S of the equator


  Create hot + dry landscapes= perfect conditions for a desert
• Low pressure along the equator and 60⁰ N/S

  Creates rainy conditions. Temperature is higher at the equator- so it is hot + wet =perfect conditions for tropical rainforests. It is milder at 60⁰ N- so cool + wet= deciduous forest

  
• How are tropical storms caused?

  1. Sea surface temperature is at or above 26.5°C, sea is at least 60 metres deep

  2. Water from the surface of the sea evaporates and the warm air rises

  3. This causes an area of low pressure over the sea

  4. The Coriolis effect makes the winds spin and more water droplets evaporate from the ocean

  5. All of the evaporated water droplets form heavy clouds as they condense in the atmosphere

  6. The storm reaches land and its energy dissipates as it is no longer over warm water where it gets its energy from

  
• Droughts: Prolonged periods of no rain (high pressure). Saharan Africa and Middle East at risk of droughts.
• Tropical storms: strong spinning storms, also known as typhoons or hurricanes
• Droughts: more droughts in the future

  As climate change changes amount and predictability of rainfall
• Tropical storms: more storms (higher frequency)


  As sea temp will be higher, severity may increase but distribution of where they are found does not change

  
• Weather Extremes- Australia vs the UK

  • Extreme wind
  • Extreme temperature
  • Extreme precipitation
• El Nino


  The reversal of normal trade winds over the Pacific Ocean
• Normal year: trade winds go east from S. America to Australia


  Bringing low pressure (rain) in Australia and high pressure in South America (dry conditions)
• El Nino year: trade winds reverse

  So low pressure (rain) in S. America leading to flooding/landslides and high pressure (dry conditions) to Australia leading to drought and wildfires

  
• El Nino also leads to more storms in the Pacific Ocean and less storms in the Atlantic Oceans

  
• La Nina


  Years are where the normal weather patterns are more intense leading to higher than average rainfall in Australia (flooding)

  
• Causes of flash flooding in Boscastle

  1. High rainfall: the amount of rain than normally fell in a month fell in 2 hours

  2. Heavy rain in previous weeks= saturated soil which led to rapid run off

  3. The village is in a steep sided valley = fast flow into the river

  4. Confluence of 3 rivers nearby = more water in the rivers quickly
• Earth's structure


  • Crust: outer layer of earth, cool and hard rock. Crust split into oceanic crust (7km deep) and continental crust (35km deep)
  • Mantle: made of molten rock- the thickest layer of the earth
  • Outer core: temperatures reach 4000°C
  • Inner core: made of solid iron and nickel, temperatures reach 6000°C
• How + why plates move

  1. Convection Currents: hot magma in the upper mantle rises, pushes crust sitting on top of the mantle sideways, the current then cools, sinks back down and the process repeats

  2. Ridge push: new crust rises because it is warm and thin creating a ridge. It pushes older crust away from the ridge

  3. Slab pull: old crust is cooler and thicker than the hot mantle, so it sinks into the mantle
• Constructive boundary


  Plates move apart, magma rises to fill the gap, cools and hardens to create new land. Volcanoes formed here (E.g.: Iceland)
• Destructive boundary


  Oceanic and continental plate move towards each other, oceanic plate is forced under (subducted) the continental as it is denser. Friction from descending plate causes earthquakes. Melted subducted plate is erupted from volcanoes
• Conservative boundary


  Plates slide past each other, his is not a smooth process. Plate begins to stick, friction builds up. When friction is overcome, plates jerk past each other- no land is lost/gained, causing earthquakes. E.g.: San Andreas Fault, California
• Collision boundary


  Two continental plates move towards each other. They are the same density so neither is subducted. Plates fold/crumple up to make fold mountains. Friction builds up and is released to cause earthquakes (E.g.: Nepal and India)
• Shallow focus earthquakes


  Under 70km from the earth's surface. Seismic waves cause damage over a large surface area as they spread further- more destructive.
• Deep focus earthquakes


  70-700km below the earth's surface at destructive plate boundaries. Very powerful but only in a small area as seismic waves do not spread outwards.
• Shield volcanoes


  Gently sloping sides, runny lava that flows a long way down the sides of volcanoes in gentle, low pressure eruptions, found on hotspots and constructive plate boundaries.
• Composite volcanoes


  Destructive volcanoes with steep sides and high pressure, explosive eruptions (lava, ash and lahars) magma is thick and sticky and flows a short way before cooling into steep sided volcano with alternating layers of ash and lava.
• Climate= the average temperature and precipitation in one place over 30 years.
• Weather= the temperature and precipitation in one place on one day.
• Climate has not stayed the same over the earth's history of 4.5 billion years, it has had hot periods (inter glacial) and cold periods (glacial). We split up the last 4.5 billion years into time periods (and name them), in each period of time, the climate changed. The current period started 2.6 million years ago and is called the Quaternary Period. It has mostly been a glacial period lasting 100,000 years followed by interglacial (warmer) periods lasting 10,000 years. We are currently in a warmer interglacial, which started 15,000 years ago. Evidence suggests the climate of the last 200 years has been influenced by human activity, making it a much warmer period than ever before- this is because scientists have recorded higher than average temperatures since 1800.
• Humans are enhancing the greenhouse effect (making global warming more intense) through actions such as: Burning fossil fuels: coal, oil and natural gas are burnt in industry (factories) and homes for energy, lighting, heating, a cooking source and as petrol in cars- releasing CO2 + methane (greenhouse gases) adding to the layer of greenhouse gases in the atmosphere. Since industrialisation, countries are using more fossil fuels than before, this used to be ACs and now includes EDCs.
• Humans are enhancing the greenhouse effect (making global warming more intense) through actions such as: Deforestation: plants take in CO2 during photosynthesis.
• The climate of the last 200 years has been influenced by human activity, making it a much warmer period than ever before- this is because scientists have recorded higher than average temperatures since 1800
• Effects of climate change in the UK

  • Evidence of climate change
  • Global effects of climate change resulting from extreme weather and sea level rise
  • Human causes of climate change
• Greenhouse effect


  Making global warming more intense
• Human actions enhancing the greenhouse effect

  • Burning fossil fuels
  • Deforestation