The change of the public sphere, to which social web services such as networking platforms, weblogs and microblogs contribute, does also affect communication in the event of a crisis or catastrophe. Beforehand, social web applications are mainly relevant an additional channel for general preparatory information on how to behave in the event of a crisis. During a crisis or a natural disaster (such as hurricanes, floods, or earthquakes) social web applications support the "situational awareness” of affected persons, but also for crisis committees, who can get hold of eyewitness accounts. Communication offerings of professional media and official institutions are important, also because users further distribute their content.
After a crisis, personal public spheres in the social web may contribute to people handling their experiences, grieving, and mentally coping with their experiences. Also in order to mobilise support or raise donations, in part even on a worldwide scale, Facebook and Twitter are being used. Problems and barriers of using the social web in crises scenarios can result from the disparate spreading and lacking trust in the public. The extension of information sources in the social web can also bring orientation problems through intransparent, redundant, or contradictory information.