Types of Hazards (Edexcel IGCSE Geography)

Anatomy of Natural Hazards

Spec point — 4GE1-S3.044

Natural hazards

• A hazard is an event which has the potential to cause harm to the environment, people or the economy

• A natural hazard is an event caused by environmental processes

• A disaster occurs when harm actually occurs to the environment, people or the economy

• Natural hazards can be categorised by their causes

  • Tectonic and geological hazards include:

    • earthquakes, volcanic eruptions, landslides and tsunami

  • Climate and meteorological hazards include:

    • Drought
    • Blizzard/snowstorm/sandstorm
    • Heatwave
    • Tornado/cyclone
    • Wildfire/forest fire
    • Extreme rainfall/flash flood caused by extreme rainfall
    • Severe storm/thunderstorm

  • Biological hazards include:

    • pests and diseases

• Natural events only become hazards and disasters due to their impact on people, the environment or the economy

• Natural hazards can also be categorised in a range of other ways:

  • Magnitude - the strength/power of the event
  • **Frequency **- how often the event occurs
  • Size - the area covered by the hazard
  • Duration - the time a hazard event lasts
  • Location - where a hazard event occurs

• Hazard** risk r**efers to the likelihood of an event causing harm to people, the environment or the economy

• Different locations have different levels of vulnerability

  • This refers to location features which affect how susceptible an area is to a hazard event

Tropical cyclones

• Tropical cyclones are rotating, low-pressure systems (below 950mb)

• They are known as hurricanes, cyclones and typhoons in different areas of the world

• Characteristics include:

  • heavy rainfall
  • high wind speeds(over 119 kmph)
  • high waves and storm surges

• Measuring between 100-1000km across the rotating clouds surround a central, calm eye

• The magnitude of tropical cyclones is measured on the Saffir-Simpson Scale from 1 to 5

• They develop in tropical regions between 5^o and 30^o north and south of the equator

Map showing the global distribution of tropical cyclones

Earthquakes

• An earthquake is a sudden, violent shaking of the ground
• Earthquakes occur at all types of plate boundaries
• Earthquakes are the result of pressure building when tectonic plates move

Map showing global earthquake distribution

• The epicentre is the point on the Earth's surface directly above the focus
• The focus is the point at which the earthquake starts below the Earth's surface

Features of an earthquake

Measuring earthquake magnitude

• The magnitude (strength/power) of earthquakes is measured on either the Richter Scale or the Moment Magnitude Scale

Measuring earthquake magnitude

• The damage caused by earthquakes is measured on the Mercalli Scale

The Mercalli Scale

Volcanoes

• Volcanoes form when magma erupts onto the Earth's surface as lava
• Most volcanoes occur at constructive (divergent) and destructive (convergent) plate boundaries
• The majority of active volcanoes are located around the rim of the Pacific Ocean called the 'Ring of Fire'

Map showing global volcano distribution

• Hotspots occur away from plate boundaries and are plumes/columns of magma which escape through the Earth's crust

Measuring eruption magnitude

• The magnitude of a volcanic eruption is measured on the Volcanic Explosivity Index (VEI)

The volcanic explosivity index (VEI)

Exam Hint When describing the distribution of hazards from a map, ask yourself the following questions;

• What is the general pattern?
• Does the pattern relate to anything else for example the location of plate boundaries?
• Are they near the equator or further away?
• Are they inland or coastal?

Use map features to help with your description - place names, compass rose, latitude and longitude