Natural Hazards Typical Mistakes and Examiners Tips!

Typical Mistakes:

• Tectonic plates comprise of both the crust and the lithosphere - not just the crust! It is wrong to assume that earthquakes and volcanic activity are confined to plate margins. Many earthquakes occur along fault lines thousands of kilometers from plate boundaries. Volcanic activity also occurs outside plate boundary zones, for example, Hawaii, Market Rasen in Lincolnshire.

• A common mistake is to oversimplify the causes and nature of volcanic activity. Explanations must take account of different processes operating at both destructive and constructive plate margins, and at hotspots as well as different products of volcanic eruptions - magma, lava, tephra, gases, pyroclastic flows etc.

• The distinction between natural events such as volcanic eruptions, and natural hazards, that cause death and damage to property. Molten rock below the Earth's surface is known as magma. Magma extruded at the surface is lava. All igneous features have formed from magma that cooled below the surface.

Examiners Tips:

• Remember that the scientific evidence that clinched the theory of continental drift is sea-floor spreading (1962 Hess)

• Landforms associated with plate boundaries depend on whether (A) a boundary is destructive/constructive/conservative and (B) the nature of the lithosphere/crust on either side of the boundary

• The key to understanding contrasting eruptive behaviour at destructive and constructive plate margins is the viscosity of magma and the extent to which gases such as steam can escape easily

• Shield volcanoes, formed from baslatic lava, are also a feature of constructive plate margins as well as hotspots.

• Key terms and terminology should be used throughout and learnt thoroughly

• The starting point for an exam answer that assesses the impact of a volcanic eruption should be a recognition that impact is essentially the result of two factors - exposure and vulnerability

• A common examination theme is the management of natural hazards and its effectiveness. Good answers will make close reference to examples of specific hazardous events.

• Another common examination theme is the relationship between earthquake magnitude and intensity. It is important to remember that earthquake magnitude is only one of several factors that influence the impact of earthquakes, and that overall, the relationship is weak.

• In any analysis of earthquake impact it is important that you support arguments with examples and case studies drawn from countries at contrasting levels of economic development

• The construction of earthquake-resistant buildings has been a success in rich countries such as Japan and has saved countless lives. This success should be contrased with the situation in many LEDCs, where buildings collapse during major earthquake events invariably leadds to massive loss of life.

• In any analysis of the threat posed by natural hazards, the exceptional nature of tsunamis - the limited effectiveness of any physical protection and their impact often thousands of kilometers from their origin - should be emphasised.