"Collapse of a considerable area of land surface, due to the removal of liquid or solid underlying or removal of soluble material by means of water". (UNDHA, DM Glossary, 1992, 72)
B. Wayne Blanchard, Guide To Emergency Management and Related Terms, Definitions, Concepts, Acronyms, Organizations, Programs, Guidance, Executive Orders & Legislation, A Tutorial on Emergency Management, Broadly Defined, Past and Present, B. Wayne Blanchard, USA 2007 (Last Modified 2008). http://training.fema.gov/EMIWeb/edu/docs/terms%20a nd%20definitions/Terms%20and%20Definitions.pdf, (Emr Mgt/ ND and Other Dzstr - Amer) {11}