Anatomy of Natural Hazards
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 & Geological | Climatic & Meteorological | Biological |
Earthquake |
Storms |
Pests |
Volcanic eruption |
Floods |
Diseases |
Landslides |
Droughts |
|
Tsunami |
Tornadoes |
- 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 5o and 30o 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 measured 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
Exam Tip
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