U1: Tectonic hazards

• How do tectonic hazards form at destructive plate margins?

  Oceanic plate subducts under continental plate
• What happens due to friction between tectonic plates?

  It causes an earthquake
• How do collision plate boundaries affect the Earth's surface?

  They lead to the formation of fold mountains
• What happens when two continental plates meet at a collision boundary?

  Both plates cannot subduct
• What is the result of two continental plates being of equal density?

  They form fold mountains
• What is the relationship between tectonic hazards and earthquakes?

  Earthquakes occur due to tectonic plate friction
• A hazard is a naturally occuring event that is a risk to people and property.
• Climatic hazards:

  • Tornado
  • Drought
  • Flood
  • Typhoon
  • Lightning
  • Hurricane
  • Heat wave
• Tectonic hazard:

  • Tsunami
  • Earthquake
  • Volcano
• Geomorphic hazard:

  • Mudslide
  • Landslide
  • Avalanche
• Crust:

  • Thinnest layer
  • 2 types; oceanic or continental
• Lithosphere:

  • Broken into tectonic plates
  • Around 100km thick
  • Solid
• Core:

  • Centre
  • Huge amount of pressure and heat
  • inner core = solid
  • outer core = liquid
• Asthenosphere:

  • denser and weaker layer
  • about 100km - 400km below surface
  • around 1300C (semi-molten)
• Lower mantle:

  • Under upper mantle
  • hotter and denser than upper mantle
• Tectonic plates:

  • Philippine plate
  • Eurasian plate
  • Cocos plate
  • Carribean plate
  • Arabian plate
  • Indo-Australian plate
  • Pacific plate
  • Nazca plate
  • Antarctica plate
  • African plate

  
• Why do the Earth's plates move?

  Convection currents

  • Cores temperature is around 6000C
  • This causes magma to rise and then cool causing it to sink again
  • Repeats causing a current flow to carry plates

  Ridge push and slab pull

  • When the plates subduct into the mantle and pull the rest of the plate with it
• Constructive margins:

  • Upper part of mantle melts
  • Hot magma rises
  • Tectonic plates moves away
  • Magma rises in between, then cools to form rock
  • Causes (small) earthquakes, due to magma pushing plate up (causing friction)
  • Over time and many eruptions, a shield volcano forms

  
• Destructive margins:

  1. Convection currents push 2 plates together, causing friction
  2. Oceanic (denser) subducts under Continental
  3. Oceanic melts into magma, which rise in continental plate to magma chamber, eventually forming composite volcanos.
  4. The plates also fold, causing fold mountains (eg. Andes)
  5. Where oceanic subducts, an oceanic trench is formed (eg. Mariana Trench)

  
• Conservative margins:

  • 2 plates sliding past eachother at different paces
  • DOESN'T form volcanoes
  • Earthquakes (big and small)

  
• (Destructive) Collision margin:

  • Continental into continental
  • Both plates too light to subduct
  • Form fold mountains (eg. Himalayas, Alps)
  • Rare volcanic activity
  • Violent earthquakes

  
• Why live in danger zone?

  Farming

  • Volcanic soils are <1% of Earths surface but contribute to 10% of population
  • Eg. Mt. Vesuvius, Italy (Grapes)

  Family or friends

  • Religious beliefs may make people stay
  • Family and friend nearby

  Tourism

  • 300,000 people visit Mt. St. Helens, USA every year
  • Tourism brings money
  • Scenery
  • Hot springs

  Mining

  • Eg. Kawah ijen, Indonesia (sulphur lake)
  • Average wage of $6 a day
  • Last 40 years, over 70 miners died due to the fumes

  Geothermal Energy

  • nearly 90% of Icelandic home heating is Geothermal energy
  • 30% of Icelands electricity
• What do seismologists use to measure radon gas in the soil?

  Radon detecting devices
• Why is it difficult to predict earthquake locations?

  Because they are hard to predict, but patterns may exist
• How can smartphones assist in earthquake detection?

  They have GPS receivers and accelerometers
• What are some planning strategies for earthquake risk management?

  • Establish exclusion zones
  • Conduct earthquake drills (e.g., Japan on September 1st)
  • Use earthquake checklists from organizations like the American Red Cross
• What are the mitigation strategies for earthquake-resistant buildings?

  • Reinforced lattice work in bedrock
  • Birdcage interlocking steel frame
  • Rubber shock-absorbers in foundation
  • Reinforced lifts with suspension cables