Hazards

• What are geophysical hazards?

  Hazards caused by land processes such as earthquakes and volcanoes.
• Atmospheric hazards


  Caused by climatic processes- e.g. tropical cyclones, storms, droughts, extremes of hot or cold weather and wildfires
• Hydrological hazards


  Caused by water movement eg. floods and avalanches
• What is the UN definition of a disaster

  10+ killed / 100 affected / declaration of state of emergency / request for international assistance
• Hazard


  Event in populated area
• Event


  Does not impact human life
• Risk


  Probability of a hazard occurring and there being a loss of life/livelihoods
• Vulnerability


  The risk of exposure to hazards combined with an inability to cope with them
• Fatalism


  Belief that hazards cannot be avoided, hazards are natural and losses are accepted
• Risk sharing


  Share cost of reducing a hazard (Insurance)
• Magnitude


  Inversely proportional to frequency, size of event
• Advantage of high frequency


  Well-prepared to mitigate and adapt as they are familiar with it, less magnitude
• Disadvantage of high frequency

  Might not fully recover from previous hazard before the next
• Areal extent


  Area affected
• Evidence for continental drift

  1) continental fit, 2) similarity of fossil plants and animals, 3) similarity of rock sequences, 4) paleomagnetism
• Theory 1: Mantle convection currents


  Circular currents in the mantle caused by the magma being heated by the core off the Earth.
• Theory 2: Slab pull and ridge push

  Added to convection currents in the 1960s to suggest Ridge-Push boundaries create new oceanic crust and Slab pull boundaries drag oceanic crust underneath into the mantle (recycling and destroying it), suggesting they work together as one like a conveyer belt.
• What are two major characteristics of the seafloor related to seafloor spreading?

  The age of the seafloor is progressively older away from mid-ocean ridges.

  The elevation of the seafloor is progressively lower away from mid-ocean ridges.
• How does the magnetic history of the seafloor relate to seafloor spreading?

  The magnetic history of the seafloor bears the striped-pattern of the Earth's magnetic reversals.
• What is the significance of older parts of the seafloor in seafloor spreading?

  Older parts of the seafloor have the greatest potential to have accumulated sediments over the longest time.
• What are constructive margin features related to ocean ridges?

  Ocean ridge: plates move apart e.g. Mid-Atlantic ridge, underwater volcanoes erupt and can build up to reach surface to form islands e.g. Surtsey. Sea-floor spreading - new crust created
• What geological formation is associated with rising magma causing crustal bulging and fracturing?

  Rift valleys are formed when rising magma causes the crust to bulge and fracture, creating faults. The land between faults drops down to form a rift valley, as seen in the East African Rift Valley.
• How do volcanoes form in constructive margins?

  Volcanoes are created when magma rises to the surface, leading to the formation of new land. Basaltic lava, with its low viscosity, flows easily. These volcanoes are typically shield volcanoes, characterized by their low, wide shapes.
• What geological event can occur due to pressure buildup from plate movements at constructive margins?

  Earthquakes can occur at constructive margins when pressure builds up from plates moving at different speeds. These earthquakes are generally of low magnitude.
• What landforms are created by Oceanic-Continental Convergent boundaries?

  Fold mountains, Volcanoes, Deep sea trenches, Earthquakes
• How are fold mountains formed at Oceanic-Continental Convergent boundaries?


  Sediments on continental crust fold upwards (Andes Mountain)
• What type of volcanoes are formed at Oceanic-Continental Convergent boundaries?

  Eruptions at subduction zones are usually infrequent but violent, often forming stratovolcanoes or composite volcanoes with a characteristic cone shape.
• What geological process leads to the formation of deep sea trenches at Oceanic-Continental Convergent boundaries (and give an example)?

  Subduction of oceanic plate under continental plate (Peru-Chile Trench)
• What causes earthquakes at Oceanic-Continental Convergent boundaries?

  Pressure build-up as plates get stuck and then slip
• What is an example of an Island Arc formed at an Oceanic-Oceanic Convergent boundary?

  Mariana Islands
• What feature is associated with Oceanic-Oceanic Convergent boundaries and is the deepest part of the ocean (and give an example)?

  Deep sea trench (e.g. Mariana Trench)
• What geological phenomenon occurs due to the pressure buildup as plates move together in Continental-Continental convergence?

  Earthquakes
• What are the stages of the Park Model related to disasters?

  Pre-disaster, Disruption, Relief, Rehabilitation, Reconstruction
• What happens during the 'Disruption' stage of the Park Model?

  Destruction and deaths occur during or immediately after the disaster.
• What is the focus of the 'Relief' stage in the Park Model?

  Rescue efforts focus on saving lives and minimizing further damage in the aftermath of the disaster.
• What is the goal of the 'Rehabilitation' stage in the Park Model?

  To resolve longer-term impacts by providing temporary shelter and aid once the immediate impacts are under control.
• What is the purpose of the 'Reconstruction' stage in the Park Model?

  To rebuild the affected area to either the same or an improved standard after the disaster.
• Advantages of Park model


  + Helps predict resources needed at each stage, Improvement mitigates future impacts, reduces vulnerability, curve tracks progress over time
• Disadvantages of Park model

  - Assumes normality, doesn't factor in events in quick succession, LIC/NEE may not be able to afford improvements
• What is mitigation in the Hazard Management Cycle?

  Minimising the impact of future disasters, such as building flood defences.