Major contributions to the study of natural hazards have been made by human geographers, or at least by geographers who note that consideration of human vulnerability to extreme events is the major factor influencing impacts. Some researchers have therefore suggested that the adjective 'natural' is inappropriate when referring to many hazard events, such as earthquakes in slum-housing areas and drought in the Sahel. Early studies of natural hazards placed too great an emphasis on the significance of natural events at the expense of human considerations when examining the characteristics of and responses to natural hazards, although a more balanced approach is now more common. There is also an increasing emphasis placed on the role of'technological' hazards, exemplified by nuclear-reactor accidents, such as at Chernobyl, and toxic-vapour escapes, such as at Bhopal. While recognising the importance of these recent developments, the emphasis in this chapter is on a balanced presentation of physical and human aspects of hazards.