Humans constantly face natural hazards on different scales in time and space. Geological, hydrometeorological and geophysical hazards adversely affect human life and health as well as having a dramatic impact on sustainable development of society. There exists an inherent danger to vulnerable lifelines and infrastructure such as water supply and reservoirs, pipelines, and power plants. The impact that these extreme events can have on developing nations can have severe repercussions on the life and economic development of these nations within minutes and throw them back for decades. The Organising Committee for the 2011 workshop on Extreme Natural Hazards and Disasters in Africa would therefore like to invite researchers world-wide to Pretoria, South Africa in 2011, to participate in an exciting, multi-disciplinary workshop to be presented by the International Union of Geodesy and Geophysics ( IUGG), International Geographical Union (IGU), International Society of Photogrammetry and Remote Sensing (ISPRS), International Union of Geological Sciences (IUGS), International Union of Theoretical and Applied Mechanics (IUTAM), Gloal Ocean Observing System (GOOS) of the Intergovernmental Oceanographic Commission, UNESCO, and American Geophysical Union . The workshop is a part of activity in the framework of the ISCU Project “Extreme Natural Hazards and Societal Implications- ENHANS”. Detailed information on the project is available on the website http://www.ENHANS.org A special GOOS (Global Oceanic Observing System) session at the Pretoria workshop will focus on the importance of maintaining sustained ocean observing systems both to prevent and mitigate disasters, where possible, but also in order to rapidly bring observing assets to bear in post disaster relief efforts. Both natural coastal inundation hazards, such as storm surges and tsunamis, as well as anthropogenic hazards, such as oil spills, will be discussed, with focus on African concerns. In the context of global sea-level rise, the session will probe the interface between physical and social sciences in order to clearly distinguish between patterns of climatic and environmental change, and patterns of risk and vulnerability.