The potential hazards posed by Mount Rainier led to its inclusion as one of the sixteen volcanoes worldwide to be designated Decade Volcanoes. The Decade Volcano initiative is part of a United Nations program aimed at better utilizing science and emergency management to reduce the severity of natural disasters. Mount Rainier was chosen to be studied because it is representative of one or more volcanic hazards: it is geologically active as evidenced by surface manifestation of heat (geothermal activity), it has had recent volcanic events (last eruption was about 150 years ago), and it is likely to erupt again, based on past history; its location poses significant hazards to a heavily populated area; it is a well known volcano (a number of research publications have been written on it); it is politically and physically accessible for study; and its volcanic geology is well exposed.