A natural phenomenon is a physical or non-artificial event. A natural phenomenon is not produced by humans although it may occur to/on/in humans (i.e. bacteria, ageing, natural disaster). Examples include volcanic eruption, growth and decay. See also geological phenomenon.

References:

“What are natural hazards” In: Disaster, Planning and Development: Managing Natural Hazards to Reduce Loss. 1990. Department of Regional Development and Environment Executive Secretariat for Economic and Social Affairs Organization of American States. Organization of American States Washington, D.C. Updated: December 1990. Accessed: April 2005.

<http://www.oas.org/usde/publications/Unit/oea54e/ch05.htm>

Lewis, Antony. 2004. Word Web Online Dictionary: University of Princeton. <http://www.wordwebonline.com/en/NATURALPHENOMENON>