Disasters are sudden, unanticipated tragedies that may be caused by nature, such as tornadoes, hurricanes, earthquakes and floods. Humans also cause disasters by accidents such as explosions, transportation accidents and fires.
Other human causes include war, terrorism and epidemics. Disasters can also be man-made. These disasters include chemical explosions, oil spills and nuclear power plant accidents.
Natural Hazards are elements of circumstances in the Natural environment that have the potential to cause harm to people or property or both.
As compared to natural hazards, natural disasters are relatively sudden and cause large scale, widespread death, loss of property and disturbance to social systems and life over which people have a little or no control.
Disasters are routinely divided into natural or human-made, although complex disasters, where there is no single root cause, are more common in developing countries.
A specific disaster may spawn a secondary disaster that increases the impact. A classic example is an earthquake that causes a tsunami, resulting in coastal flooding. Some manufactured disasters have been ascribed to nature.