A natural disaster is a major adverse event resulting from natural processes of the Earth; examples include floods, hurricanes, tornadoes, volcanic eruptions, earthquakes, tsunamis, storms, and other geologic processes.
Natural hazards are extreme natural events that can cause loss of life, extreme damage to property and disrupt human activities. Some natural hazards, such as flooding, can happen anywhere in the world. Other natural hazards, such as tornadoes, can only happen in specific areas. And some hazards need climatic or tectonic conditions to occur, for example tropical storms or volcanic eruptions. Human activities can influence how often certain natural hazards occur and how severe they are. Understanding when, where, why and how natural hazards occur can help us to understand how to minimise their impact on our lives.
Types of natural hazard
Natural hazards can be placed into two categories - tectonic hazards and climatic hazards. Tectonic hazards occur when the Earth's crust moves. For example, when the plates move, friction can cause them to become stuck. Tension builds until the plates release, which leads to an earthquake. Climatic hazards occur when a region has certain weather conditions, for example heavy rainfall can lead to flooding.
Hazard risks - economic, social and environmental consequences
Hazards can have economic, social and environmental consequences. For each hazard event the risks, or probability, of a particular consequence occurring can vary greatly. This depends on certain factors. For example in a developing country, the death toll tends to be high but the short-term economic costs are often relatively low, whereas in a developed country, the death toll tends to be low but the short-term economic costs can be extremely high. The long-term situation is more complex. Developing countries can be slower to repair damage to roads and buildings. This can lead to a reduction in tourists and therefore a long-term loss of valuable income. Hazard risks are increasing due to population growth, urbanisation, pressure on marginal land and changes to the natural environment.
