In December 1941, an avalanche of glacial ice in the Cordillera Blanca of Central Peru caused two highland lakes to abruptly empty their contents into the valley below. This massive outburst flood swept through the modern heart of Huaraz, the regional capital, then charged another 220 kilometers down the Santa River Valley to the Pacific, leaving 5,000 dead in its wake. This phenomenon and its close relative the huayco flood are as old as the Andes themselves, but Mark Carey is the first historian to write a book about society’s relationship to this natural hazard and the glaciers that shape the high Andes. He convincingly demonstrates that melting ice has been a dominant factor in the regional history of Peru’s Callejon de Huaylas since the disaster of 1941. But the book deserves a wide readership for what it tells us about the relationship between the state, society, science, and environmental change in the modern Andes. Key themes include the rise of technocrats and the impact of neoliberalism, and it vividly reveals the challenges that vulnerable peoples have already begun to face as a result of global warming.Unlike some disaster studies, this book does not get bogged down in describing death and destruction. Instead, it focuses on society’s response to disaster. Political confrontations and social movements provide the book with most of its drama. Social and political historians will greatly appreciate Carey’s delineation of the actors involved. Scientific experts, engineers, and technocrats are central to the story, often serving as mediators between other social groups. Urban groups were most directly affected by this hazard and most vocal about what to do about it. Rural indigenous groups also played an influential role in these controversies, as did water and hydropower developers, central government officials, and even foreign ecotourists and NASA. Carey is remarkably evenhanded in appraising the positions of these actor groups, to the point that he avoids criticizing Lake Commission experts for withholding evidence of imminent danger facing valley residents.This book conveys an overall tone of optimism — a great rarity in a disaster study. It is a history of the power and influence of the popular classes and regional elites, not of their victimization or marginalization at the hands of outsiders. Expanding on the findings of Anthony Oliver-Smith regarding the 1970 earthquake and avalanche that almost obliterated Yungay, Carey identifies repeated instances in which locals successfully inserted themselves into the decision-making process affecting their livelihoods and resisted external pressure to resettle elsewhere after disasters. But Carey also points out that residents of the Cordillera Blanca, in the process, became far more dependent on the Peruvian state and on scientific and technological experts for their well-being, as an unintended consequence of getting what they wanted. Tensions are continuing to rise now that the safety of so many valley residents has been handed over to private water and hydroelectric developers as a result of the neoliberal turn of the 1990s.Those desiring evidence that global warming is influencing these disasters will be disappointed that Carey makes little reference to this research. The latest ice-core studies from Mt. Huascarán (the peak towering above Yungay) show that high-altitude temperatures in this part of the Andes have risen very quickly during the 75-year period covered by this study, though not as abruptly as the dramatic temperature oscillation of the eighteenth century, which presumably caused similar disasters. The book also gives very limited attention to the direct influence of these events on developments outside of the region, such as the failure of the import-substituting coal-steel complex built in Chimbote, and that city’s explosive transformation into the world’s largest fish-producing port. The book introduces, but never fully develops, the intriguing theoretical concept of “disaster economics” — the use of disaster by certain groups to promote development. Carey also could have done even more to explore the ramifications of his findings for broader historical trends in Latin America and around the globe, such as growing conflict over freshwater supplies stored in this rapidly disappearing frozen environment (although he does this in other publications).All in all, this book is a model regional study, with a keen sense of place and the peoples who inhabit it. In the Shadow of Melting Glaciers has been awarded the Conference on Latin American History’s 2011 Elinor Melville Prize for the best book on Latin American environmental history. Hopefully, this much-deserved honor will not distract social and political historians from recognizing the book’s significance to their own concerns.