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

• 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

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 100-2000km 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

Distribution of Tropical Cyclones

Earthquakes

• 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
• 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
• The magnitude of earthquakes is measure on either the?Richter Scale?or the?Moment Magnitude Scale
• The damage caused by earthquakes is measured on the?Mercalli Scale

Earthquake Distribution

Volcanoes

• 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'
• Hotspots occur away from plate boundaries and are plumes/columns of magma which escape through the Earth's crust
• The magnitude of a volcanic eruption is measured on the?Volcanic Explosivity Index (VEI)

Active Volcano Distribution