AQA AS/A-Level Geography Exam Practice Answers

AQA AS/A-level Geography exam practice answers 5: Hazards

1 Most volcanic activity is associated with plate tectonic [6] processes and is mainly located along plate margins. Volcanic activity is found at:  oceanic ridges: where plates are moving apart and magma is forcing its way to the surface, cooling and forming new crust. Volcanoes formed here have fairly gentle sides because of the low viscosity of the basaltic lava. Eruptions are frequent but relatively gentle  subduction zones: the deeper the oceanic plate descends, the hotter the surroundings become, heat generated from friction begins to melt the oceanic plate into magma in a part of the subduction zone known as the Benioff zone. Plutons of magma reach the surface and form volcanoes. The andesitic lava, which flows easily, creates complex, composite and explosive volcanoes  hot spots: in some locations a concentration of radioactive elements below the crust causes a hot spot to develop. A plume of magma rises, when this lava breaks through to the surface, active volcanoes form above the spot.

2 The storm basically originates from an area of low pressure, [6] where surface heating results in warm air being drawn in a spiralling manner. Several conditions need to be present:  an oceanic location with sea temperatures over 27°C  an ocean depth of over 70 m (the moisture provides latent heat and the cold water is not stirred up by the storm from the deeper ocean)  a location 5° north or south of the equator – so that the Coriolis force brings about maximum rotation  convergence of air in the lower atmosphere  rapid outflow of air in the upper atmosphere. 3 The lithosphere is divided into seven large and three smaller [9] tectonic plates – rigid rafts of rock floating on the underlying semi-molten mantle (the athenoshere). The plates are moved by convection currents operating as convection cells within the athenoshere. They can move towards each other (destructive plate margins) and away from each other (constructive plate margins). They can slip alongside each other (conservative plate

Hodder Education © 2017 1 margins). Most plate movement is slow and continuous but sudden movements produce earthquakes. Diagrams may be used to show location of earthquake activity at different types of plate boundary. Reference to types of movement – ridge push and slab pull. 4 Attempts to predict: [9]  monitoring groundwater levels  release of radon gas  strange animal behaviour  measuring of magnetic fields  hazard zone maps can be acted upon by national and local planners. Prevention of seismic natural events is impossible. Some scientists are looking into reducing the friction caused at conservative plate boundaries. Preparation measures include:  promoting understanding of earthquakes and their effects  understanding of how homes can be adapted to better withstand the impacts of earthquakes  well practised and understood safety drills  modification of impact by appropriate insurances  building of hazard-resistant structures, e.g. rubber shock absorbers in foundations, cross-bracing to hold structures together and allow flexibility as a building shakes  fire prevention – ‘smart meters’ have been developed to cut off gas supplies if an earthquake of a high magnitude occurs  careful education, training and preparation of emergency services  land use planning – putting certain types of building in low-risk areas  tsunami protection, e.g. automated warning systems; however, large tsunamis can overwhelm these. Evaluation of the success will refer to examples and may cover limitations of cost, expertise and lack of access to the latest technology, reliance on aid and foreign donors in the aftermath, poor planning and lack of government focus.

5 Answer will depend on the choice of example but will include [9] discussion of:  risk and vulnerability  level of preparation  access to resources  skill and training of emergency services  response of government  response of foreign countries