Hostile Earth (Part 1)

In this mini-series we’ll be exploring the destructive side of the Earth, its effects and how we can help to protect ourselves. (This will also cover everything you need to know for Unit 2 of  AQA GCSE Geography!)

Plate Margins

Conservative

  • 2 plates slide past each other, travelling in opposite directions
  • Activity: violent earthquakes
  • Example: San Andreas Fault in California (Pacific & North American plates)

Destructive

  • An oceanic plate moves towards a continental plate, but because it is heavier it sinks and is destroyed, forming deep-sea trenches  and island arcs. Volcanoes also form as the extra magma created from the destroyed oceanic plate is under pressure and is forced upwards through the rock.
  • Activity: violent volcanic & violent earthquakes
  • Example: Chile (Nazca & South American plates)

Constructive (aka Sea-Floor Spreading)

  • 2 plates move apart forming new oceanic crust as well as mid-ocean ridges with volcanoes
  • Activity: gentle volcanic and gentle earthquakes
  • Example: Mid-Atlantic Ridge (e.g. Iceland) (North American & Eurasian plates)

Collision

  • 2 continental crusts collide and as neither can sink they are forced upwards, creating fold mountains
  • Activity: violent earthquakes
  • Example: The Himilayas (Eurasian & Indo-Australian plates)

MEDC Case Study – Kobe, Japan

  • Plate Margin: Destructive
  • Plates: Eurasian & Phillipenes
  • Location: Urban
  • Local Date & Time: 17th January 1995 05:46 a.m.
  • Magnitude: 7.2
  • Primary effects: 200,000 buildings collapsed, 3/4 all quays destroyed, 10 bridges along the bullet train route collapsed, 1 km of Hanshin highway collapsed
  • Secondary effects: 5,500 dead, 40,000 injured, 230,000 homeless when temps averaged -2 degrees, fires from ruptured gas/electricity mains, grid-locked roads, lack of water supplies, industries shut down

LEDC Case Study – Sichuan, China

  • Plate Margin: Conservative
  • Plates: Eurasian & Indo-Australian
  • Location: Rural
  • Local Date & Time: 12th May 2008 02:30 p.m.  
  • Magnitude: 7.9
  • Primary effects: 7,000 classrooms and most buildings collapsed, communication (e.g. phone lines) destroyed, landslides, hospitals destroyed
  • Secondary effects: 70,000 dead, 40,000 injured, 4.8 million homeless, 70% roads blocked, 46 million affected in total, 18,000 still missing presumed dead, $86 billion damage, isolation of villages in remote areas

Reducing the risks from earthquakes

Key definitions

  • Prediction: the use of science/technology to monitor techtonic activity
  • Preparation: creating emergency plans to implement once the disaster has struck
  • Planning: e.g. building design – earthquake-proofing buildings in urban areas to reduce damage, injuries & death
  • Retrofitting: addition of new technology to older buildings
  • Appropriate technology: technology designed with consideration of intended community

In an MEDC…

  • Computer controlled counterweight on roof
  • Cross-bracing to add strength and prevent twisting
  • Automatic window shutters stopping shattered glass#
  • Automatic sprinklers to prevent fires

In an LEDC…

  • Roof made of reinforced concrete
  • Hollow concrete bricks which cause less damage if they fall
  • Foundations made mainly of stone from the remains of previously destroyed buildings
  • Relatively cheap and uses recycled materials

Special Case: Costa Rica

  • Bamboo homes – bamboo is strong but also flexible so less likely buildings will collapse. More environmentally friendly as only 70 hectares of land needed to build 1000 homes compared to 600 hectares of forest.

How to prepare your home:

  • Secure heavy, moveable items of furniture
  • Prepare an earthquake kit
  • Practice earthquake drills (e.g. Disaster Prevention Day in Japan)
  • After the shaking stops check for injuries and check the radio for further instructions
  • Building codes – homes built in at-risk areas must have strong earthquake-proofing

Preperation for and Response to Earthquakes..

MEDC

  • Local services are well trained and regularly have practice drills
  • New buildings comply with strict earthquake planning regulations
  • Emergency earthquake kits packed
  • Education – teach people what to expect in the event of an earthquake
  • Counselling for distressed children
  • Viible identification numbers on roofs to help helicopters assess damage

LEDC

  • Looks to international aid and world-wide charities for help
  • Cremate the dead to prevent disease
  • Airfields that bring in rescue teams and emergency supplies are often too far away
  • Poorly built buildings
  • Limited supplies for a large number of victims
  • Makeshift open-air hospitals
  • Limited funds to cover cost of supplies and rebuilding projects
  • Lack of radio/tv/internet that could communicate with people to allow time to evacuatedanger zones or help manage relief operations

Both

  • Evacuation centres in safe areas
  • Community ready and willing to search for victims/survivors but lacks the appropriate equipment
  • Monitoring movementss in the Earth’s crust
  • Massive disruption to power lines transport and communications