Abstract This chapter summarizes the processes and effects of the most notable catastrophic mass movement events in South America in the twentieth century. We present 23 case histories of individual and regional landslide events, beginning at the northeast terminus of the Andes Mountains in Venezuela, proceeding counterclockwise down the Pacific Coast to the southern Andes of Chile and Argentina, and ending with discussion of catastrophic regional mass movements in the Brazilian Highlands. The types of landslides involved in these disasters ranged from high-velocity rockslides and rock or debris avalanches to high- to medium-velocity debris flows and mudflows. Most casualties were caused by high-velocity debris avalanches and high-to medium-velocity, highly mobile, long-runout debris flows. A common, and particularly devastating, regional occurrence consisted of earthquake-triggered slides on steep slopes covered with saturated residual soils; these slides were rapidly transformed into very fluid, high-velocity debris avalanches, which in turn changed into devastating debris flows that ran out into populated areas on valley bottoms.

Abstract This chapter discusses some of the ways volcanic activity can affect structures, developments, facilities, and other engineering works. It is vitally important to recognize the possible effects of volcanic activity on these works of man. The large variety of volcano-related hazards now recognized records a marked recent growth in the understanding of these phenomena. The increasing application of systematic observation and analysis to current volcano-related events and to old deposits of previous events throughout the world has greatly increased our understanding of volcanic phenomena; the threat to life and property from these hazards can now be significantly reduced or avoided by careful forethought by geological scientists, engineers, and planners. Public demand, however, may prevent the withdrawal from use of lands that are affected only once in hundreds or thousands of years, and a low degree of risk in such places may be judged to be economically and socially acceptable. Volcanic eruptions are widely known and feared, yet few of their specific effects are familiar to most people. Volcanoes affect people in many positive ways; for example, erupted materials commonly produce highly fertile soils. However, the immediate effects of volcanoes on people and their engineering works are frequently negative. Although in many countries volcanic activity is a constant and severe threat, it represents only an occasional danger in the United States. That danger is serious enough, however, to warrant preparatory planning in Hawaii, Alaska, and other western states. Nonexplosive eruptions that produce lava flows are familiar volcanic phenomena; although they present little danger to people’s lives, they can severely damage property.