Spectacular volcanic scenery and features were the inspiration for creating many of our national parks and monuments and continue to enhance the visitor experience today (Table 1). At the same time, several of these parks include active and potentially active volcanoes that could pose serious hazards - earthquakes, mudflows, and hydrothermal explosions, as well as eruptions - events that would profoundly affect park visitors, employees, and infrastructure. Although most parks are in relatively remote areas, those with high visitation have daily populations during the peak season equivalent to those of moderate-sized cities. For example, Yellowstone and Grand Teton national parks can have a combined daily population of 80,000 during the summer, with total annual visitation of 7 million. Nearly 3 million people enter Hawai`i Volcanoes National Park every year, where the on-going (since 1983) eruption of Kilauea presents the challenge of keeping visitors out of harm's way while still allowing them to enjoy the volcano's spellbinding activity.