A natural disaster is any event of force of nature that is caused by environmental factors that has catastrophic consequences. Natural disasters include: avalanches, earthquakes, floods, hurricanes, impact events, landslides, mudslides, tornadoes, tsunamis, tropical cyclones, typhoons, and volcanic eruptions. http://www.mnui.com/international-insurance-definitions/
A natural disaster is the consequence or effect of a natural, hazardous event, occurring when human activities and natural phenomenon (a physical event, such as a volcanic eruption, earthquake, hurricane, tsunami, landslide, etc.) become enmeshed. Natural disasters result in catastrophic consequences for living things in the vicinity. This understanding is crystallized in the formulation: "disasters occur when hazards meet vulnerability.
A natural disaster is an event with a nature, as opposed to human, which cause results in large-scale loss of life or damage to property. It could be related to weather, geology, biology or even factors outside the Earth. Examples are earthquakes, hurricanes, droughts and flooding.