Abstract Lowering of the land surface of large areas has been a major unintended consequence of groundwater and petroleum withdrawal by humans. Approximately 26,000 km 2 of land in the United States has been permanently lowered. The decrease of land-surface elevation, known as land subsidence, typically occurs at rates measured in centimeters per year. However, the irreversible accumulation of its effects clearly qualifies humans as major geologic agents. Subsidence causes permanent inundation of land, aggravates flooding, changes topographic gradients, ruptures the land surface, and reduces the capacity of aquifers to store water. This paper reviews the mechanism, occurrence and history, impacts, and efforts by society to control land subsidence caused by underground fluid withdrawal in the United States.

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Abstract Geologists have investigated many different types of subsidence (Table 1) in North America during the past 100 years. Their principal contribution has been a better understanding of subsidence processes associated with the sudden formation of sinkholes, volcanic activity (Schuster and Mullineaux, this volume), tectonism (Bonilla, this volume), and sediment compaction induced by withdrawal or natural expulsion of underground fluids. Although major advancements in the understanding of other types of subsidence processes have been made primarily by engineers and soil scientists, geologists have outlined the geologic framework within which these subsidence processes are active. Allen (1969) provides an overview of the geologic processes that contribute to subsidence and the geologic setting of subsidence. This chapter traces the evolution during the past 100 years of the conceptual understanding of land subsidence in North America caused by compaction of unconsolidated sediment induced primarily by the withdrawal of underground fluids. It reviews the ways these concepts have been applied, both to development of the theory of fluid flow through porous media and to gain insight into natural geologic processes. Four important case histories are examined, and the chapter concludes with discussions of the outlook for future investigations of subsidence in North America and a summary of research needs. Terminology used in the chapter follows Poland and others (1972). Subsidence associated with man-induced compaction is one of man’s major inadvertent engineering feats. At least 34 areas in Mexico and the United States have subsided (Fig. 1); an aggregate area of about 22,000 km 2 , approximately equal to the area of New Jersey, has been lowered more than 30 cm.

Abstract How would you feel if your land had sunk 9 m in the past 50 years because of human activity? It happened in the San Joaquin Valley. In fact, land subsidence has been caused by man’s activities in at least 37 of the 50 states of the United States and affects more than 40,000 km2 in this country alone. Data from a few sites where economic impact is documented suggest a total annual cost to the nation of more than $100 million; worldwide, the total economic impact is astounding and growing. These nine papers, dedicated to Joseph Fairfield Poland's life work, constitute a major contribution to measuring and understanding this problem. They are arranged in three categories: (1) fluid withdrawal from porous media; (2) drainage of organic soil; and (3) collapse into man-made and natural cavities.