Sample Answer

Describe and explain the distribution of major earthquakes (4)

The major earthquakes are located on the edge of continents or in the middle of the sea. There are 3 main belts that can be identified: Circum Pacific, mid-Atlantic and Alpine Himalayan belt. All of the earthquakes occur along the edge of the plate margins. They occur at all types of plate movements, including convergence, divergence and torsion. The movement of the plates at about 3-5 cm a year, lead to the build up and sudden release of pressure, which causes earthquakes.

For an earthquake or volcanic eruption you have studied, describe the short-term and long-term responses to the disaster (6)

Mount Soufriere erupted dramatically on the island of Montserrat on 25th June 1997. The short-term response to the eruption was to evacuate Plymouth and the airport. An emergency support unit was activated to assist with search and rescue. The UK Navy Battleship, HMS Liverpool sent personnel ashore to provide assistance; emergency food and medicine for animals were brought in for animals suffering malnutrition and dehydration.

The longer term response to the eruption was development in the north of the island away from the areas at risk of the volcano. The British Government invested £56 million including providing £6.5 million towards an emergency housing scheme, upgrading the hospital at St John`s and providing an assisted passage scheme to aid relocation for those wanting to leave the island.

Suggest why the loss of life was so great in Sumatra, part of an LEDC (4)

The loss of life in Sumatra was high due to a number of reasons. Firstly, Sumatra was the closest island to the epicentre of the earthquake so will have felt the strongest effect of the shock waves. The earthquake was also very powerful, being the second worst with a magnitude of 9.3 on the Richter scale. Another reason why there will have been a huge loss of life is that the population density on Sumatra could be high, thus a lot of people would be at risk. This is made worse by the fact that Sumatra is an LEDC and will lack the resources to deal properly with such a hazard. The warning systems would not be as effective in a MEDC and many of the buildings will be of poor quality materials and not built to withstand a major earthquake.

Explain the characteristics of shield volcanoes and how they are formed. (6)

Shield volcanoes have a wide base with gentle sided slopes. They are made up of basic lava which means that they tend to erupt quite frequently but are not explosive in nature. They are formed either along a constructive plate margin where diverging plates create fractures through which the lava erupts or, as in the case of the Hawaiian volcanoes they occur as a result of hot spots. The basic nature of the lava makes it less explosive. As the lava has a low viscosity, it flows a long way before cooling and solidifying, leading to the broad base and gentle slopes typical of a shield volcano.