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Solid-Earth Sciences and Society 5 Hazards, Land Use, and Environmental Change ESSAY: A FRACTION OF THE EARTH'S SURFACE The surface is the interface between the Sun-powered processes dominated by erosion and deposition and the tectonic processes driven by the Earth's internal energy. Most of the surface lies at two general levels: nearly 60 percent is between 1 and 5 km below sea level, and about 25 percent lies within a kilometer above or below sea level (Figure 5.1). The remaining 15 percent of the surface is concentrated in tectonically active mountain belts, continental slopes, and oceanic trenches. The part of the surface most heavily populated is usually less than 1 km above sea level; most activities are concentrated in areas not far above sea level. Mountainous areas usually are sparsely populated because they are less favorable to agriculture, construction, and transportation and are more susceptible to hazards. Such areas tend to be used for specialized agricultural activities, mining, and recreation. In places where large populations concentrate in or close to structurally active mountainous regions—for example, those in Armenia, Chile, Nepal, and California—the residents are faced with special problems in developing the land resource because of the risk of seismic, volcanic, and landslide hazards. Just at sea level—within the zone affected by tidal and storm-generated oscillations—spreads the biologically diverse region of environmentally sensitive terrains: marshes, swamps, tidal flats, and fens. Historically, such expanses were considered wastelands or were drained, filled, or surrounded by sea walls to increase their agricultural worth. Research conducted within the past 50 years has disclosed the inadvisability of such projects because they can disturb the natural breeding habitats of wildlife and the cleansing functions of the world's wetlands. Close study shows that wetlands constitute whole ecosystems supporting vast populations, not only of waterfowl, reptiles, and amphibians but also microscopic creatures. Coastal wetlands abound in unfamiliar fungal and bacterial species that perform the invaluable tasks of isolating and neutralizing the toxic compounds flushed through the system in the hydrologic cycle. The shallow-water area of the continental shelf is recognized as essential to fisheries and as a source of significant oil and gas production. The most recent ocean-waters flooding of the continental shelves took place within the past 10,000 years, and the nature of this geologically transient environment is as yet
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Solid-Earth Sciences and Society FIGURE 5.1 Curve showing the cumulative percentage of the area of the Earth that is higher than any particular elevation. Most of the surface lies either 3 and 5 km below sea level or within 1 km above sea level. Human activities are concentrated in the areas that are less than 1 km above sea level. poorly understood. Research techniques such as advanced side-scanning sonar systems are aiding in the study of the continental shelves. If sea levels rise more rapidly over the next century, interest in the continental shelf environment will intensify, and the use of land surfaces below sea level may extend beyond the Netherlands, where it is now focused. Great attention is given to sudden landform changes such as abrupt changes of elevation during earthquakes, yet more money is spent yearly in attempts to retard the slow changes of landform development than on mitigation of the effects of sudden change. The incremental changes produced by erosion and deposition lead to soil loss; silting of reservoirs; and destructive transformations of hillslopes, rivers, and coastlines. Such evolution is natural and often inevitable. The activities of humankind have commonly accelerated the transformations, catapulting natural systems over thresholds and producing immediate environmental threats. The geomorphological processes affected by humans cover a staggering range of scale. From local denudation caused by livestock overgrazing, a significant component of the process of regional desertification, humankind has evolved into a major geomorphological agent. Proper understanding of progressive geomorphological changes can forestall precipitous transformations and prevent the loss of landform stability. Landforms are not random features; they are the consequences of the interplay of constructive and destructive geological and hydrologic forces requiring careful study before they can safely be artificially modified. Our baselines for understanding processes at the surface are disturbingly short, although existing landscapes provide important information about the magnitudes and return frequencies for many natural processes. Only in the past century have detailed
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Solid-Earth Sciences and Society observations been made concerning such features as flood intensities and frequencies, debris-flow distribution, subsidence, and landslides. Thus, predictions are based on recent to current conditions that are known to have been altered by human actions. Predictions of longer-term events, such as 1,000-year floods, are very unreliable because they must be based on models with uncertain numerical characteristics. Landforms are sensitive to climatic change because the operating rates of the processes that mold landforms vary dramatically with climate. Fluvial processes dominate in sculpting landforms in semiarid regions, while wind processes are more significant in arid regions. Under very wet climatic conditions, landslides and downhill movements of surface rocks are dominant. Each of these geomorphic processes leaves distinctive evidence in the geological record. When climate changes, the dominant land-forming processes change in response. Threshold values of rainfall and temperature can be defined at which a change from the dominance of one land-forming process to another is likely to occur. It is therefore possible to forecast how agricultural regions might shift size and location in response to global warming and related changes in rainfall. On an even longer time scale, low-lying coastal areas are subject to episodic flooding as sea level oscillates. Most remarkable are the paleo-landscapes locally exposed by erosion beneath extensive blankets of sedimentary rocks that have been deposited on the continents during flooding episodes. Glacial valleys 450-million-years old are evident at central Saharan sites now occupied by desert wadis, a 170-million-year-old sea stack lies fallen on a modern beach in Scotland, and a tropical beach 450-million-years old can be visited on the outskirts of Quebec City. The long-term durability of low-lying continental surfaces—less than 1 km above sea level and less than 0.2 km below sea level—that is demonstrated by landscape exhumation can be seen on much shorter time scales by the slow rates of erosion that characterize such flat areas. The occurrence of these extensive areas of low relief, coupled with a suitable climate, makes regions such as the American Midwest prime land resources. The lush agricultural production of such regions can be maintained only if the landscape is treated with the same conservation ethic that inspires reverence for parks and wilderness areas. Prevention of soil erosion and respect for natural ecological balances in low-lying, low-relief regions can ensure their productivity far into the future. Geological characterization forms an essential basis for planned preservation and maintenance. Human society exists in the biosphere, which thrives at the boundary layer between the solid-earth and its fluid envelopes, perched between the two engines of mantle convection and solar energy that drive geological processes. The biosphere, composed of chemical elements that are cycled among the reservoirs of the atmosphere, hydrosphere, crust, and mantle, also contributes to cycles of rapid chemical turnover and thus functions as a part of the geological processes. The more vigorous manifestations of those processes, however, regularly destroy the parts of the biosphere—and its human constructions—located in their paths. As society has increased its utilization of earth resources and expanded its population and area of colonization, the frequency of its encounters with vigorous geological processes has increased. Society has adopted a term, geological hazards, for these perfectly normal processes that began occurring long before humans arrived on the scene. Many of the most tragic episodes in the natural history of humans have been related to geological hazards such as disastrous floods, earthquakes, sea waves, landslides, and volcanic eruptions. The fact is that most geological hazards can be avoided or mitigated through proper land-use planning, engineered design and construction practices, building of containment facilities such as dams, use
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Solid-Earth Sciences and Society of preventive measures such as stabilization of landslides, and development of effective prediction and public warning systems. In many parts of the world such measures have already significantly reduced human suffering from geological hazards, although major challenges remain. To further mitigate these hardships, it is essential that a better fundamental understanding of each hazard-causing geological phenomenon be gained and widely disseminated. Before the development of agriculture, the effects of human beings on the Earth were comparable to the effects of other species. But the onset of crop cultivation and animal domestication, with the subsequent growth of urban civilizations, introduced a new set of forces. Today, humans are changing basic earth processes in unprecedented ways and to unfamiliar degrees. At present, every person in the United States is responsible on average for the consumption of 16 metric tonnes—about 35,000 lb—of minerals and fossil fuels each year. This use does not include the tremendous volume of material moved during the construction of homes, parking lots, office buildings, factories, dams, highways, and other structures. On a worldwide basis, the human population uses nearly 50 billion metric tonnes of earth materials each year. This amount is more than three times the quantity of sediment transported to the sea by all the rivers of the world. Clearly, human beings have become a geological agent that must be taken into account in considering the workings of the earth system. The various materials moved by human society are perturbing not only the physical cycles of the Earth, by increasing mass transfer, but also the chemical aspects. The biogeochemical and geochemical cycles that convert elements into living creatures, and into ore deposits and other geological concentrates, now have new aspects. The chemicals generated by manufacturing and the disposal of materials, including toxic compounds, occur in concentrations and combinations never before involved in natural systems. The consequences of such contaminations are poorly understood. Some earth systems operating at the boundaries of the geosphere, hydrosphere, atmosphere, and biosphere are very fragile, and every human effort toward survival or improvement of the human condition necessarily results in repercussions on those systems. We dispose of our wastes in the same sedimentary basins that supply us with the bulk of our groundwater, energy, and mineral resources. Through our social, industrial, and agricultural activities, we are changing the composition of the atmosphere, with potentially serious effects on climate and terrestrial and marine ecosystems. The human population is expanding into less habitable parts of the world—steeper mountainsides, more ephemeral deltaic and barrier islands—which increases vulnerability to natural hazards and strains the biological and geological systems that sustain life. In this sense, geological conditions control the quality of human life. People all over the Earth are constantly moving from less economically viable rural areas to the crowded cities in hopes of achieving a better livelihood. Wastes produced in and around the cities further compromise the quality of surrounding lands, and consequently there is a strong need for urban renewal or recycling of crowded urban spaces. With the crowding and densification of urban living comes an increased need for more uses of recycled land space. Buildings and other structures for human habitation, transport, or manufacturing are made taller and heavier. They may be founded on sites that are less than optimal for resisting the physical stress induced by their presence. Geology is the main interconnecting element between the craft of civil engineering and the intricacies of nature. It is being used in efforts addressing water quality, resource supply, waste isolation, and disaster mitigation to accommodate and reduce the adverse effects of societal growth. If present trends continue, the integrity of the more fragile systems on which
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Solid-Earth Sciences and Society human society is built cannot be assured. The time scale on which these systems might break down may be decades or it may be centuries. Human beings are unique among the influences on the Earth—we have the ability to foresee possible consequences of our activities, to devise alternative courses, to weigh the pros and cons of these alternatives, to make decisions, and then to behave accordingly. Understanding the natural systems acting at the land surface presents a major scientific challenge because of the enormous social implications of those systems. Land resources, as basic elements of the global ecosystem, profoundly affect the lives of every human being on the face of the Earth. The loss of topsoil and forests, the loss of life and property caused by human-induced geomorphic change, and the pollution of air, soil, and water all result in growing consequences for both national and international welfare and security. GEOMORPHIC HAZARDS Landforms are continually changing, but except for a few spectacular instances their change is so gradual that it is scarcely noted. As population increases, more people are exposed to the effects of processes that have been going on for hundreds of millions of years. In many cases the increase in human population contributes to instability of the physical landscape. When human populations are threatened by geomorphic processes, those processes become geomorphic hazards. Great attention is given to hazards representing abrupt changes, such as earthquakes and volcanic eruptions, but more damage is caused and more money has to be spent annually in attempts to retard ongoing hazards such as landslides, debris flows, and the normal slow progression of erosion and redeposition that leads to soil loss; reservoir infilling; and river, coastline, and hillslope changes. The surface of the land is shaped by internal forces—folding and faulting with consequent elevation or subsidence—and by erosion—wind and water weathering driven by solar energy and gravity. Wind and water accomplish erosion by forcibly loosening, removing, and transporting solid material. That eroded material becomes the sediment deposited elsewhere. Erosion and sediment production result from the exposure of earth materials and from variations of climate, vegetation, and topographic relief. For materials of similar strength, natural sediment production reaches a maximum at about 33 cm of rainfall per year. Below that amount, less runoff causes less removal of material; above that amount, increased vegetation protects the soil so the amount of erosion and sediment production decreases. Modern erosion rates can be very high, because both urban and agricultural development require removal of the original vegetation. Geomorphic hazards may involve a slow progressive change in a landform (Figure 5.2) that, although in no sense catastrophic, can become a significant hazard involving costly preventive and corrective measures. There are three types of geomorphic hazards that combine different spans of time, different degrees of damage, and different energy expenditures. The most obvious type is a sudden event that produces an abrupt change—a landslide caused by monsoonal rains, an earthquake, or human activity such as removal of toe support from a stable slope (Figure 5.3). A second type is progressive change that leads to an abrupt result, typified by weathering breakdown of soil or rock that initiates slope failure, gullying of a steepening alluvial fan, meander growth and cutoff, or stream channel shifting. The final type of progressive change gradually produces a slowly developing geomorphic hazard—for example, gradual hillslope erosion, gradual meander shift, channel incision, or channel enlargement. Misidentifying or wrongly estimating the pace of progressive changes may result in incurring pointless protective or remedial costs. Accurate identification of impending problems attributable to slow progressive change can aid in the choice of remedial action and in prudent allocation of money toward engineered hazard prevention. Geomorphologists have quantified ways of identifying potential hazard sites that suggest future change. When historical information is available, it may be possible to make a crude estimate of the timing of landform failure. But, usually, too many influences operating on too fine a scale make it difficult to predict when a failure will occur.
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Solid-Earth Sciences and Society FIGURE 5.2 Principal forms of mass movement, as correlated with dominant mechanisms of falling, sliding, and flowing. Each block represents a form that can characterize single or multiple events of ground failure; in many occurrences one form can give way to another, as indicated by dashed lines and arrows. Blocks in center and at left represent failure in bedrock, those in center and at right failure in surficial deposits. After R. H. Jahns, NRC, 1978, in Geophysical Predictions. Increased erosion of productive agricultural soils has grown into a serious problem, both for the farmer and for those downstream who must cope with siltation. Soil erosion is accelerated by a variety of agricultural practices, including cultivating slopes at too steep an angle and irrigating with too much water or water under pressure. Under certain circumstances, erosion can proceed so rapidly and over so wide an area that remote sensing techniques may be the best way to monitor it. In situations that require estimates of slow erosion rates from significant topographic features, radioactive isotopic analysis can help in establishing chronologies of erosion surfaces and stratigraphic horizons. Historically, the greatest amount of erosion in the eastern United States and resulting sediment transport by streams probably occurred in the eighteenth century as agriculture first became widespread. Estuaries became severely silted at that time. In the nineteenth century the western United States experienced a similar development; the process was documented in the Colorado River Basin during the 1880s as extensive channel incision developed in tributary valleys and created the characteristic ar- FIGURE 5.3 Ranges in general rates of movement for landslides and related features. Dashed parts of horizontal bars represent relatively uncommon or poorly documented occurrences. After R. H. Jahns, NRC, 1978, in Geophysical Predictions.
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Solid-Earth Sciences and Society FIGURE 5.4 April 1983 Thistle, Utah, landslide. The landslide flowed down the valley damming Spanish Fork Canyon. Photograph courtesy of Gerald F. Wieczorek, U.S. Geological Survey. royos. Sediment samples taken since 1930 show a significant decrease in sediment loads, suggesting that the incised channels have reached a new state of relative stability. This new equilibrium may result from a combination of conditions: less material is being eroded, and more of the sediment that is produced is being held up in the valleys, where it is deposited in newly developing floodplains. This trend has been enhanced by dam construction. The reservoirs extending behind the dams are clogging up with sediment, drawing attention to the long-term obsolescence of such facilities. In time the renewable resource of water for hydropower and agriculture may become severely compromised. On the lower Mississippi River, a 50 percent decrease in sediment transport has been associated with dam construction upstream on the Missouri River and bank stabilization elsewhere (see Figure 1.11). The Mississippi delta is being modified as the rate of sediment delivery decreases, and the natural slow subsidence due to basin deformation and sediment compaction outruns sediment accumulation, thereby permitting the sea to encroach onto the land. Landslides and Debris Flows In the 1970s, landslides—all categories of gravity-related slope failures in earth materials—caused nearly 600 deaths per year worldwide. About 90 percent of the deaths occurred in the circum-Pacific countries. Annual landslide losses in the United States, Japan, Italy, and India have been estimated at $1 billion or more for each country. Landslide costs include direct and indirect losses affecting both public and private property (Figure 5.4). Direct costs can be defined as the costs of replacement, repair, or maintenance of damaged property or installations. An example of direct costs resulting from a single major event is the $200-million loss attributed to the 21-million-m 3 landslide and debris flow at Thistle, Utah, in 1983. The slide severed three major transportation arteries—U.S. highways 6 and 89 and the main line of the Denver and Rio Grande Western Railroad—and the lake it impounded by damming the Spanish Fork River inundated the town of Thistle, resulting in the destruction of businesses, homes, and railway switching yards. The indirect costs involved the cutoff of eastbound coal shipments along the railroad line. In 1983 oil was expensive and coal was crucial for generating electricity. With supplies from the west severed, eastern coal normally exported to Europe had to be rerouted. European industry, in turn, had to adjust to lowered supply. Ultimately, the landslide affected the international balance of payments. Destructive landslides have been noted in European and Asian records for over three millennia. The oldest recorded landslides occurred in Hunan Province in central China 3,700 years ago, when earthquake-induced landslides dammed the Yi and Lo rivers. Since then, slope failures have caused untold numbers of casualties and huge economic losses. In many countries, expenses related to landslides are immense and apparently growing. In addition to killing people, slope failures destroy or damage residential and industrial developments as well as agricultural and forest lands, and they eventually degrade the quality of water in rivers and streams. Landslides are often associated with other events: freeze-thaw episodes, torrential rains, floods, earthquakes, or volcanic activity. The bulging of the surface of Mount St. Helens over a rising magma body
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Solid-Earth Sciences and Society FIGURE 5.5 Sections through Mount St. Helens showing early development of rockslide-avalanche into three blocks (I, II, III) and explosions emitted primarily from block II; fine stipple shows preexisting domes and coarse stipple shows the 1980 cryptodome. After J. G. Moore and C. J Rice, NRC, 1984, in Explosive Volcanism: Inception, Evolution, and Hazards. led to a massive air-blast landslide—2.8 km3 of rock, the largest slide in recorded history. Loosened material slipped off the side of the growing dome, unroofing the magma and permitting it to degas in a spectacular and locally disastrous eruption (Figure 5.5). The volcanic ash, dust, and pumice, mixed with rain and snowmelt, caused widespread debris flows in local valleys. A minor volcanic event high on the slopes of Nevado del Ruiz volcano in Colombia in 1985 melted enough glacial snow and ice to produce a debris flow that killed 25,000 people in the valley below. An earthquake off the coast of Peru in 1970 initiated a rockfall on Mt. Huascaran in the high Andes. The rockfall turned into a debris avalanche that moved at speeds approaching 300 km per hour and killed more than 20,000 people in the towns of Yungay and Ranrahirca. Very large slides also are found on slopes below sea level. In the area around the Hawaiian Islands, recently discovered slide debris covers about 15,000 km2 and contains single blocks more than a kilometer thick that slide as much as 235 km away from the shallower water. A major problem in the Gulf of Mexico is slumping, which can disrupt seafloor pipelines and the foundations for drilling platforms worth hundreds of millions of dollars. In Hawaii the debris is well-consolidated basaltic lava, while in the Gulf of Mexico it is unconsolidated, or at best semiconsolidated, clastic sediments. In the geological record, boundaries of rock masses representing such major slides could very well be confused with the effects of tectonic faults; indeed, distinctions between the largest landslides and gravity-driven faults may be in the eye of the beholder. Despite improvements in recognition, prediction, mitigative measures, and warning systems, worldwide landslide losses—of lives and property—are increasing, and the trend is expected to continue into the twenty-first century. Some of the causes for this increase are continued deforestation, possible increased regional precipitation due to short-term changing climate patterns, and, most important, increased human population. Demographic projections estimate that by 2025 the world's population will number more than 8 billion people. The urban population will increase to 5.1 billion—more than the total number of humans alive today (Figure 5.6). In the United FIGURE 5.6 Urbanization compared with world population growth since 1800. Modified after Davis, 1965, Scientific American.
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Solid-Earth Sciences and Society States the land areas of the 142 cities with populations greater than 100,000 increased by 19 percent in the 15-year period from 1970 to 1985. By the year 2000, 363,000 km2 in the conterminous United States will have been paved or built on. This is an area about the size of the state of Montana. Accommodation of this population pressure will call for large volumes of geological materials in the construction of buildings, transportation routes, mines and quarries, dams and reservoirs, canals, and communication systems. All of these activities can contribute to the increase of damaging slope failures. In other countries, particularly developing nations, the urbanization pattern is being repeated but often without adequate land planning, zoning, or engineering. Not only do development projects draw people, but the projects themselves as well as the people who settle the surrounding area often occupy just those hillside slopes that are susceptible to sliding. At present, there is no organized program to provide the geological studies that could prevent the worst scenarios posed by this threat. To reduce landslide losses, research efforts should encompass more than investigations of physical processes in hazardous areas aimed at understanding the nature of slope movement. Earth scientists also need to perfect methods for identifying areas at risk and for mitigating contributory factors. These goals are attainable. Scientists can predict areas at risk and advise means to avoid or moderate danger, but much of the research needed has yet to be done. For the past half century, geologists have relied primarily on aerial photography and field studies—ideally in combination—for identification of vulnerable slopes and recognition of landslides. In recent years, since multispectral satellite coverage has become available for much of the world, an additional tool is available that can provide images in black and white or color as well as spectral bands through red, green, and near-infrared wavelengths. The coverage, scale, and quality of multispectral imagery is expected to improve considerably within the next decades and provide valuable information that can lead to improved identification of landslide-prone locations. The information gathered from satellite reconnaissance can contribute to the growing store made use of in geographic information systems, which are digital systems of mapping spatial distribution that can be applied to the preparation of landslide susceptibility maps (Figure 5.7). These modern data-handling systems facilitate both pattern recognition and model building. Patterns and models that suggest landslide susceptibility can be tested, revised and improved, and then tested again against large numbers of observations. As a result of these gains in knowledge, progress has been made in determining appropriate types of landslide mitigation. The most traditional mitigation technique is avoidance: keep away from areas at risk. When occupation of a site warrants risk, engineered control structures may be required, including surface water diversion and subsurface water drains, the construction of restraining structures such as walls and buttresses, and devices such as rock bolts. The establishment and enforcement of site grading codes calling for appropriate slope stabilization instituted in 1952 by Los Angeles County have worked well. Cut-and-fill grading techniques involving the removal of material from the slope head, regrading of uneven slopes, and hillslope benching are all of proven value. Consideration of such factors has had a major effect on reducing landslide losses in the United States, Canada, the European nations, the former Soviet Union, Japan, China, and other countries. Landslide research today is focused not so much on locating where landslides are and what hazards they represent as on figuring out how to cope with the potential hazard that they represent. This is an area of close cooperation between solid-earth scientists and geotechnical engineers. Mitigation has also benefitted from substantial progress in the development of physical warning systems for impending landslides. Significant improvement will result as better instrumentation and communication systems are developed. Of particular importance will be continuing advances in computer technology and satellite communications. Hazard-interaction problems require a shift in perspective from the incrementalism of individual hazards to a broader systems approach. Earth scientists, engineers, land-use planners, and public officials are becoming aware of interactive natural hazards that occur simultaneously or in sequence and that produce cumulative effects that differ from those of their component hazards acting separately. In the case of landslides, research is particularly needed on cause-and-effect relationships with other geological hazards. For example, in the 1991 Mount Pinatubo (Philippines) eruption, the thick accumulating ash-fall and ash-flow deposits proved particularly liable to generate landslides and debris flows during typhoons. Research on the social aspects of such relationships in terms of warning systems and emergency services is necessary. At what point should people evacuate and abandon their little piece of the Earth?
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Solid-Earth Sciences and Society FIGURE 5.7 Landslide susceptibility map (D) produced using geographic information systems methods of a part of San Mateo County, California, near the town of La Honda. A landslide inventory map (B) was compared with a geological map (A) and a slope map (C) to determine the percentage of each geological unit that has failed by landsliding in the past, and the slope important for the failure. These data formed the matrix for the susceptibility analysis (D). The higher the roman numeral, the more susceptible the slope is to landsliding in the future. Landslide deposits (L) are shown as a separate category (highest). This map was used by San Mateo County to reduce potential development in landslide-prone areas and to require detailed geological studies to determine the safety of building sites. Figure from Earl Brabb, U.S. Geological Survey. Human intervention can reduce landslide risk by influencing some contributory causes. Projects that undermine slopes in marginal equilibrium or destabilize susceptible areas by quick drawdown of reservoirs can be avoided. Among projects that can lay the groundwork for disastrous landslides are road building, mining, fluid injection, and building construction that entails clearing vegetation. Planning and designing such projects with the local landslide potential in mind is absolutely essential. While these activities may not individually cause a landslide, they can increase the likelihood of slope failure as preconditions to which cloudbursts or earthquakes are added. Wherever hillsides receive precipitation over days and weeks, the pore-water pressure can build in rock fractures and decrease bulk shear strength, which can then induce displacements under less force than would be needed to shear a drier
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Solid-Earth Sciences and Society material. A proven mitigation technique in such cases is for geologists to locate the water surface in fractured rocks and drain off destabilizing water by drilling horizontal wells. Then there are the regional-scale contributory causes of increased landslide susceptibility such as deforestation. According to the World Resources Institute, approximately 109,000 km2 of tropical forest is being destroyed annually—an area the size of Ohio. Removal of the forest cover increases flooding, erosion, and landslide activity. This deforestation is causing serious landslide problems in many developing countries. Over a period of about 3 years in the 1980s, during the course of an El Niño episode, regional weather changes in the western United States resulted in much heavier than average precipitation in mountainous areas. That increased precipitation caused a tremendous increase in landslide activity in California, Nevada, Utah, Colorado, Washington, and Oregon. Scientists are coming to understand such cycles through integration of collected data with information found in the historical and geological records. Cycles such as El Niño form the background variation of the climate pattern. But earth scientists do not know what to expect with additional perturbation from a changing greenhouse effect. Will the predicted temperature increase cause a decrease in precipitation, as occurred in mid-America during the summer of 1988? Will it increase storm activity throughout the mid-latitudes? Will it disrupt global climatic patterns, resulting in droughts in some areas and increased precipitation in others? Documented cause-and-effect sequences such as those related to El Niño episodes suggest that if areas prone to landslides are subjected to heavier than normal precipitation, susceptible slopes are likely to fail. Land Subsidence Land subsidence can be currently observed in at least 45 states; it is estimated to cost the nation more than $125 million annually. Subsidence can have human-induced or natural causes; both are costly. In the United States at least 44,000 km2 of land has been affected by subsidence attributed to human activity, and the figure is probably higher. As for natural subsidence, one event—the 1964 Alaskan earthquake—caused an area of more than 150,000 km2 to subside as much as 2.3 m. This event was extreme but not atypical of past or probable future disturbances. The causes of subsidence are various but well known, and the hazard presented is well recognized; however, the indications of specific imminent danger and the possible cures or preventives are not clear. Subsidence can be induced by withdrawing subsurface support—by removing water, hydrocarbons, or rock without a compensating replacement. In many instances, oil or water is removed from porous host sediments that compact as the interstitial fluid is removed. In such cases, collapse is slow and gentle. More dangerous are situations that leave voids—withdrawal of water from cavernous limestone or mining of coal, salt, or metals. These voids can collapse gradually or suddenly. Not all subsidence is unexpected—ground over longwall coal mines is supposed to subside gradually to a new elevation that is both safe and stable. The ground surface above subsiding land is not a good place for a shopping center or school building, but it may be quite suitable for crops or recreation. Natural subsidence occurs for several reasons. A basin surface may warp downward in response to recent sediment loading or by dewatering and compaction of sediments; both processes presently affect the Mississippi River delta. Tracts may subside because of folding or faulting, as in the Alaskan example above. Regions such as the Texas Gulf coast are triply vulnerable because they overlie a downward-flexing part of the crust; are above a thick pile—up to 10 km deep—of compacting sediments; and are being mined for groundwater and petroleum, which accelerates deflation of the sedimentary pile. The primary cause of the most common, and most dangerous, subsidence in the United States is groundwater extraction through water supply wells. In California's San Joaquin Valley, 13,500 km2 of land surface has sunk as much as 9 m in the past 50 years because of removal of groundwater for irrigation. The danger, of course, is in more populated areas, especially those close to sea level. Some cities that are already struggling because of groundwater extraction include Houston-Galveston, Texas; Sacramento and Santa Clara, California; and Baton Rouge and New Orleans, Louisiana. The problem of induced subsidence is international and also threatens London, Bangkok, Mexico City, and Venice. If sea level continues to rise, the cities that are literally on the edge now will be fighting to stay above water. Sinkholes, another common source of land collapse, can occur unexpectedly on a more local scale than wholesale subsidence. Sinkhole collapse generally results from the slumping of poorly consolidated surficial material into underground caverns.
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Solid-Earth Sciences and Society the problem—this site was recommended by the secretary of the Department of Energy (DoE) and approved for detailed study. DoE subsequently prepared a site characterization plan, in accordance with the requirements of the Nuclear Waste Policy Act, to summarize existing information about geological conditions at the site, to describe the conceptual design, and to present plans for acquiring the necessary geological information. To date, detailed geological, seismic, and regional geophysical mapping has been accomplished, and 182 boreholes and 23 exploration trenches have been excavated within a radius of 9.5 km around the prospective site. A 1992 NRC study, Ground Water at Yucca Mountain, How High Can It Rise?, assessed the long-term outlook for this site and is a good example of the need to engage scientists with a broad range of geological and geophysical expertise. The report found no likelihood of a postulated environmental risk from future tectonic and hydrologic changes. Contaminated Water, Air Pollution, and Acid Rain Complex changes in water chemistry take place throughout the hydrologic cycle, from the time rain falls on the Earth to the time when it flows into the ocean. Some water moves quickly to streams, providing flood flows and moving large loads of sediment. Some moves through the soil and the shallow saturated groundwater system, sustaining the base flow of streams. Some water moves deeper into the crust, circulating for long periods. The deeper water becomes a major transportation system for mass and heat in the Earth and influences the complex chemical changes taking place within the crust. Since the first irrigation projects, humans have affected the flow and chemistry of water as it circulated along the surface. During this century, such influence has greatly increased. Dams have been built on many of the streams of the world. Water quantity and quality are now seriously at risk, and societally generated contamination may be the most serious of water problems. The consequences of agricultural and resource-extraction practices threaten humans by contaminating the water supply and posing a threat to the natural environment by changing ecosystems. Wastes also are released into the atmosphere, increasing particulate matter and adding greenhouse gases that prevent heat from escaping the atmosphere. Modifying the greenhouse effect has the potential to seriously disturb climate, which means a change in rainfall. Much of hydrology, as it has been practiced, and many statistics are based on the assumption that the hydrologic cycle does not change within spans of decades to centuries, in contrast with geological time. A precipitously changing climate alters the basic assumption, making a large proportion of analyses suspect. A vacillating hydrologic cycle makes deeper scientific understanding of the basic phenomena much more important. Hydrologic instability, with more intense extremes such as floods and droughts, appears to be more likely during a period of change. Predicting future climate and the associated rainfall and runoff is a great challenge to science. The atmosphere is composed principally of nitrogen and oxygen, with minor amounts of carbon dioxide and water vapor and traces of many other gaseous materials. The airborne waste products of civilization include gases such as sulfur dioxide and sulfur trioxide, nitrogen oxides, carbon dioxide, and ozone. Rainfall dissolves these gases, from the atmosphere, transporting them to the ocean. The sulfur and nitrogen species and the carbon dioxide are hydrolyzed to yield weakly acidic solutions that may still be substantially more acidic than ordinary surface waters. Eventually, these solutions will increase the acidity of the surface waters, especially in those lakes and rivers where the water acidity is poorly buffered by rocks and soils. The enhanced solubility of many major and trace constituents of ordinary rocks in acid waters releases unfamiliar elements and compounds into the water. These increasing amounts of rock-derived chemical constituents can threaten biological systems as well as the increasing acidity of the water. Much sulfurous gas comes from electricity-generating plants that burn sulfur-bearing coal and from smelters processing sulfide ores. Coal contains sulfur both as sulfur-bearing organic compounds and as iron sulfides. Although it is possible to remove some of the iron sulfide prior to burning, the organic sulfur is an integral part of the coal. Corrective approaches for coal have relied on using the lowest-sulfur coals and on scrubbing the effluent gases. Corrections for smelter emissions have principally taken the form of prohibitory regulations, which have put the smelters out of business and led to transferral of the mining-smelting industry to other countries. Limited studies of alternatives to thermal smelting—such as dissolution mining or solvent extraction of finely crushed ores—have not yet yielded widely acceptable technologies, but they offer significant scientific and technical challenges as well as long-term economic, environmental, and national security incentives.
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Solid-Earth Sciences and Society Although civilization's contribution to atmospheric acidity is a serious problem, our role can seem puny when compared with that of nature. Even modest volcanic eruptions can inject vast amounts of sulfur into the atmosphere very quickly, and they may remain airborne for several years. The sulfur disperses globally as sulfur dioxide in stratospheric aerosols and returns to the surface gradually. Scientific experience in observing such events has lately taken a leap forward with observations of the plume from the 1991 volcanic eruption of Mount Pinatubo in the Philippines. Understanding the global consequences of a major eruption is likely to be important for volcanology, for understanding waste emission, and for global change studies. Atmospheric emissions and their consequences have been reviewed repeatedly by the NRC over the past decade, and with the passage of the Clean Air Act in 1990 it became clear that the national perspective on these matters was in the process of change. Hydrologic research was the topic of a recent full-scale assessment by the NRC. Solid-earth scientists are closely involved in hydrology, and their research dominates both surface drainage and underground water. Underground hydrology plays an important role because of the need to ensure the isolation of radioactive waste and untreatable toxic fluids, both of which are considered for deep disposal only. In the past, shallow groundwater was often studied as a separate resource, assumed to be isolated from deeper waters. Modern theory recognizes the importance of shallow and deeply circulating groundwater in the hydrologic cycle and thus in environmental pollution scenarios. For example, fluid contaminants introduced into a deep formation by a waste-injection well might someday reach the biosphere through shallow aquifers, unless precautions are taken in the design of such facilities and enough research is invested to understand the hydrogeological setting. Much current research in groundwater hydrology and environmental engineering is centered on the study of contaminant transport in shallow aquifers, with respect to both fluid flow and chemical reactions. Significant progress has been made with computational and laboratory simulation of transport processes, although the problems of accurately predicting contaminant transport over human or geological time scales remain largely unsolved. In this light, studies of hydrothermal processes such as sediment diagenesis and ore mineralization may provide insight and natural analogs for verifying models of chemical transport. There are problems of cleanup and prevention of contamination in both surface water and groundwater. These involve the transport of chemical constituents by water, often with simultaneous chemical reactions. It is essential that more robust and accurate analytical models be developed for predicting the chemical fate and transport of contaminants in groundwater. Certain contaminants can be chemically remedied by means of absorption or caging, and many of the chemical reactions are controlled by microorganisms. Understanding the kinetics of complex chemical reactions in a heterogeneous medium populated by microorganisms poses an exciting, though daunting, scientific challenge. That challenge must be met. GLOBAL CHANGE Recorded history affords but a brief glimpse of environmental change, one that fails to shed light on events and conditions that may confront us in the decades ahead. Global climates may soon be warmer than at any time during the past 1 million years, and sea level may stand higher than at any time during the past 100,000 years. Within decades, we may find ourselves in the midst of a biotic crisis that rivals the most severe mass extinctions of the past 600 million years. Nature is a vast laboratory that we can never manipulate or duplicate artificially on the scale necessary to test theories of global change. In developing plans for the future, we must therefore rely heavily on observations of nature itself. Change is universal throughout the earth system, and has been since the origin of the Earth, but the term ''global change" has come to be used much more narrowly to refer to human-induced changes affecting the atmosphere, hydrosphere, and biosphere. These changes are beginning to be recognized as likely to modify our environment in unprecedented ways within the next century. While many of the processes causing the changes are not unusual, it is an accelerated rate of change that human activities have introduced into the earth system. That accelerated rate of change may prevent normal adaptation mechanisms in the atmosphere, hydrosphere, lithosphere, and biosphere from working without major consequences—at least to humans. Public interest has focused mainly on global climatic change, but the scientific community recognizes that expected changes are much broader, extending to changes in such phenomena as sea level, groundwater quality, pollution, and biodiversity. Exactly what phenomena are included as elements of global change varies, depending on the breadth of the
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Solid-Earth Sciences and Society interests of the individual scientist or policy maker concerned. Understanding Global Change The worldwide scientific community has risen to the global change challenge. Over the past decade it has begun to address such questions as how the world is changing, what might happen in the next decades, and what might be done to avert possible unwanted changes. The problems are great because the world is always changing, and the differences we would like to be able to measure are very small, especially when seen against the background of general fluctuation. The NRC has identified a set of issues and suggested possible lines of global change research (NRC, 1983, 1986). In a complimentary effort, NASA established the Earth System Science Committee (ESSC), which attempted a comprehensive assessment of how the earth system works and how satellite missions might address how it operates and how it might be changing (ESSC, 1988). Space provides the right environment from which to obtain an overall view of the planet's behavior, so it is not surprising that the NASA-sponsored study identified an important role for current and future measurements from space. Recognizing the scale and expense of the necessary programs, in the mid-1980s an interagency Committee on Earth and Environmental Sciences was established under the Federal Coordinating Council on Science, Education, and Technology with a working group on global change. In recent years, budget plans worked out through that structure have accompanied the president's budget when it has been presented to the Congress (e.g., Our Changing Planet, Office of Science and Technology Policy, 1992). These plans, which represent close cooperation among science planners in numerous agencies, reflect an integrated view of the earth system similar to that stressed in this report. The federal government's planners have assigned the highest priority to the fluid parts of the earth system—clouds, ocean circulation, and biogeochemical fluxes—but solid-earth science research has not been neglected. Two of the sets of research priorities identified are of special importance to solid-earth scientists because they relate to earth system history and solid-earth processes. The latter category includes volcanic activity, sea level change, coastal erosion, and frozen ground; earth system history focuses on paleoclimatology, paleoecology, and ancient atmospheric composition. When the scale of the national effort that would be needed for addressing the problems of global change became clear in the mid-1980s, the NRC established the Committee on Global Change (now the Board on Global Change), which has issued a number of reports, of which Research Strategies for the U.S. Global Change Research Program (NRC, 1990) is of special interest because it has a section devoted to strategies for the study of earth history. Study of the most recent past is emphasized; the past 1,000 to 2,000 years, the earlier Holocene, the most recent glacial cycle, and the past few glacial cycles are all discussed as offering specific opportunities for important research into global change. Environments of extremely warm periods and climate-biosphere connections during abrupt changes are also considered as particularly likely to yield significant research findings. Science planners in the United States have been closely involved with developments in the International Council of Scientific Unions (ICSU). An International Geosphere-Biosphere Program (IGBP) was set up under the ICSU in the mid-1980s to study global change, and the NRC's Board on Global Change acts as the U.S. National Committee for the IGBP. The IGBP defined initial core projects in 1990 (IGBP Report #12) that both supplement and complement U.S. initiatives. The international body has set up a project on past global changes; its "two-stream approach" emphasizes earth history over the past 2,000 years and the glacial-interglacial cycles in the Late Quaternary. The scientific community has clearly defined the kinds of research needed to understand global change, and the Bush administration recognized the scale of the effort by submitting programs to Congress that amounted to roughly $1 billion a year. Because measurements from space are critical and because observation over a long time is essential, costs of about $2 billion a year over 20 years could be involved. Mitigation and Remediation The NRC has lately looked at the question of what the policy implications are of global change (Policy Implications of Global Change, 1991). Among its recommendations, some specific roles for solid-earth science research may be discerned—for example, "Make greenhouse warming a key factor in planning for our future energy supply mix. . . ." Action items include: Encouraging broader use of natural gas. On both a national and a global scale, there is a clear
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Solid-Earth Sciences and Society opportunity not only for seeking out more natural gas supplies but also for applying geology and geophysics to efficient development and production. Developing and testing a new generation of nuclear reactor technology. Understanding the solid-earth will be important for nuclear fuel, waste isolation, and hazard assessment. Accelerating efforts to assess the economic and technical feasibility of carbon dioxide sequestration from fossil-fuel-based generating plants. Efforts in "clean coal" technology have concentrated strongly on high-temperature combustion and related aspects. Solid-earth scientists can identify what coals from what areas can be efficiently used most in the new technology. Other recommendations relate to forestry, agricultural research, and making the water supply more robust by coping with present variability. Solid-earth scientists through their understanding of the land surface, its drainage, and its groundwater clearly have much to contribute in all basic aspects of mitigation and remediation. Three Roles for the Solid-Earth Scientist There are three aspects of global change in which the solid-earth scientist is particularly involved. The first is understanding global change. The record of the past reveals both the extent and the pace of change. This information is useful not only in revealing the extent of past changes but also in showing how fast they have happened and in throwing light on how remote parts of the earth system have accommodated themselves to perturbations. Understanding the approaching changes will be easier if we understand what has already happened. Models of the future can be tested for validity by seeing how well they can reproduce past conditions. The past record is also important in helping to distinguish between anthropogenic change and what is sometimes called natural variability, although the involvement of the human race is hardly unnatural. The role of the solid-earth scientist in increasing understanding of global change is to document the background rates, ranges, and intensities of the environmental kaleidoscope without the factor of anthropogenic changes. That documentation can be obtained in the ways outlined in Chapter 3, The Global Environment and Its Evolution. The second aspect of global change in which solid-earth scientists will play a part is assistance in reducing the extent of future change. Increasing the world's reserves of natural gas, for example, could make more readily available a fuel that produces less carbon dioxide than most other forms of fossil hydrocarbon. Better understanding of aquifers worldwide could lead to informed management practices less likely to lead to pollution from waste disposal or to depletion of the water supply. Because the world's population is so large and is continuing to increase, some kinds of global change are inevitable. More coal burning in populous India and China over the next 20 years can hardly be avoided and cannot fail to increase the carbon dioxide content of the atmosphere faster than plausible reductions in carbon dioxide output in the most advanced communities. Some consequent climatic change in the next 50 years appears unavoidable. Because of this prospective change, there is a third useful role for solid-earth scientists in global change research: study of how to mitigate and ameliorate the effects of possible changes. The following examples illustrate how such studies could be effective. Research in areas where sea level is rising today, such as the Gulf Coast where water extraction, reduced sediment supply, and other factors have induced rapid local subsidence, is likely to pay dividends if sea level rise becomes more general in the next century. Research on the hydrology of arid lands—for example, on how transitions from desert to more moist conditions take place—can be carried out now in areas such as the Sahara-Sahel boundary. The results of such studies could prove useful if, as seems not unlikely, there are changes in the distribution of the present climatic zones of the continents in the next century. At present, models of global change are not capable of suggesting the possible extent of changes in the future, partly because of limited spatial resolution and partly because they cannot accommodate all the controlling variables. Solid-earth scientists have the opportunity to work with other earth scientists, including social scientists, in testing and refining models of the earth system that will be needed for understanding global change sufficiently well to permit informed decision making. The roles of the solid-earth scientist in understanding change, managing change, and mitigating the effects of unavoidable change are all likely to increase in importance in the next decades. RESEARCH OPPORTUNITIES The problems and the research discussed in this chapter are concerned with the major interactions
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Solid-Earth Sciences and Society between the earth sciences and society and involve many aspects of the earth system that impinge directly on the quality of life. The problems affect the daily lives of the average American more than those discussed in any other chapter of this report. The Research Framework (Table 5.1) summarizes the research opportunities identified in this chapter with reference also to other disciplinary reports and recommendations. These topics, representing significant selection and thus prioritization from a large array of research projects, are described briefly in the following section. The main topics are geological hazards and changes in the environment on global and local scales. Some changes occur naturally, and others are caused by the activities of society. Human beings are now the most significant geological agents. The topics are identified in Table 5.1 under Objective C, mitigating geological hazards, and Objective D, minimizing and adjusting to global and environmental change, but they also involve some aspects of Objective B, finding, extracting, and disposing of natural resources, and certainly depend on Objective A, understanding the processes in research themes I-IV. These themes extend from the surface into the interior and are all interrelated. Research projects commonly involve more than one theme, as was discussed in connection with the research opportunities for Chapters 3 and 4. In particular, the fluxes of material involved in the biogeochemical cycles (II), largely transported in fluids (III), have influenced changing paleoatmospheres and paleoceans (I). Research conducted during recent decades on geological processes and the causes and mechanisms of geological hazards has provided unprecedented opportunities to reduce the potential for disaster, and the International Decade for Natural Disaster Reduction is concerned with converting the opportunities into science-wrought realities. High national priority has been attached to the comprehensive U.S. Global Change Research Program, which encompasses the full range of the earth system, and many research opportunities have been identified. Objective C: To Mitigate Geological Hazards Although understanding of hazards and the engineering capacity to control them are both growing, hazard losses continue to increase because this knowledge is not reflected in engineering design and in public regulation, private policies, and investment decisions. Achievement of the mitigation objective therefore requires not only continued basic research but also attention to matters such as social science and governmental issues. These issues are the concern of the U.S. program for the International Decade for Natural Disaster Reduction. They include such items as the following: Scientific and engineering efforts aimed at closing critical gaps in knowledge to reduce loss of life and property. Guidelines and strategies for applying existing knowledge. Physical adjustments for avoiding the impacts of hazards, such as land-use planning, building site evaluation, building to withstand hazards, predicting occurrences, and preventing hazards. Social adjustments for avoiding the social effects of hazards, including land-use controls and standards, public awareness campaigns, emergency preparedness programs, and financial arrangements to spread economic loss among a larger population. Education of the public and of public officials to raise the level of awareness about how to plan for and respond to natural hazardous events. Governmental issues, including the strengthening of communication links among federal officials and among federal, state, and local levels of government and the development of efficient lines of authority for decision making, especially in multiple-hazard events. A concerted effort to identify research on any hazard that has applications to other hazards, which is very cost effective. There is clearly commonality in issues related to geological hazards, and there is therefore a strong overlap between the research needs and opportunities listed under the following subheadings. There are extraordinary opportunities in geoscience for scientists and engineers to make valuable and lasting contributions to public welfare. Earthquakes, Volcanoes, and Landslides Earthquake Prediction. Both the prediction of events and the assessment of associated hazards emphasize cross-disciplinary research that draws on seismology, geodesy, geochemistry, hydrology, tectonics, and geomorphology. The most recent large events in the best-instrumented seismogenic regions are particularly important as sources of potential understanding and of new ways of thinking, such as that represented by a dynamical systems approach. There is a continuing need to improve dialogue about seismic risk between solid-earth scientists and engineers and decision makers, as well
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Solid-Earth Sciences and Society TABLE 5.1 Research Opportunities Objectives Research Areas A B C. Mitigate Geological Hazards—Earthquakes, Volcanoes, Landslides D. Minimize Perturbations from Global and Environmental Change—Assess, Mitigate, Remediate I. Global Paleoenvironments and Biological Evolution ■ Environmental impact of mining coal ■ Past global change ■ Catastrophic changes in the past ■ Solid-earth processes in global change ■ Global data base of present-day measurements ■ Climatic effects of volcanic emissions II. Global Geochemical and Biogeochemical Cycles ■ Soil processes and microbiology ■ Earth science/materials/medical research ■ Biological control of organic chemical reactions ■ Geochemistry of waste management III. Fluids in and on the Earth ■ Seismic safety of reservoirs ■ Precursory phenomena and volcanic eruptions ■ Volume-changing soils ■ Isolation of radioactive waste ■ Groundwater protection ■ Waste disposal: landfills ■ Cleanup of hazardous waste ■ New mining technologies ■ Waste disposal from mining operations ■ Disposal of spent reactor material IV. Crustal Dynamics: Ocean and Continent ■ Earthquake prediction ■ Paleoseismology ■ Geological mapping ■ Remote sensing of volcanoes ■ Quaternary tectonics ■ Soil cohesion ■ Landslide susceptibility maps ■ Landslide prevention ■ Age-dating techniques ■ Real-time geology ■ Systems approach to geomorphology ■ Extreme events modifying the landscape ■ Geographic information systems ■ Land use and reuse ■ Hazard-interaction problems ■ Detection of neotectonic features ■ Bearing capacity of weathered rocks ■ Urban planning and underground space ■ Geophysical subsurface exploration ■ Detection of underground voids V. Core and Mantle Dynamics Facilities, Equipment, Data Bases ■ Global data base of present-day measurements for detection of future changes ■ Geographic information systems ■ Remote sensing from satellites ■ Dating techniques ■ Geophysical techniques for subsurface exploration in engineering ■ New mining technologies ■ New methods for fracture sealing ■ Methods to densify soils ■ Geophysical techniques for subsurface exploration ■ Global data base of present-day geochemical and geophysical measurements Education: Schools, Universities, Public ■ Essential to devise ways to inform the public and policy makers about the scientific basis for understanding geological hazards and environmental changes
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Solid-Earth Sciences and Society as to become fully aware of how risk is perceived in the community at large. Many societies cannot afford earthquake-resistant construction, and even those that can retain large inventories of structures that are far below the state of the art in design and construction. Seismic Safety of Reservoirs. Reservoir safety needs continued research on topics such as proximity to active faults, reservoir-induced seismicity, and the known seismicity of particular areas. Paleoseismology. Development of data in the new subdiscipline paleoseismology has provided a sufficiently long historical sample to permit the identification of patterns and rates of occurrence of large earthquakes. For example, great earthquakes in intracontinental regions are now known to recur at intervals as long as several thousand years, and seismically quiescent periods between clusters of events on a given fault system may be hundreds of thousands of years long. Precursory Phenomena and Volcanic Eruptions. Basic research in geology, petrology, geochemistry, and geophysics (see Chapter 2) is required in order to understand what triggers volcanic eruptions and how to predict them. Eruptions are generally preceded by seismic activity as volcanoes are reactivated, and the activity may include destructive earthquakes. Geological Mapping. Mapping of potentially active volcanoes to determine their past eruptive history and their eruptive frequency, with the help of new dating methods, is an effective, low-cost way of reducing risk from volcanic eruptions themselves and from the associated devastating mudflows. Our present ability to predict along which of the radial directions from a volcano's center the brunt of explosive or mudflow destruction is likely to be directed is especially useful. Satellite-Based Surveying Systems and Remote Sensing. These observation techniques offer great potential for monitoring the hundreds of potentially active volcanoes that have not been mapped and for measuring the increased temperatures associated with rising magma below the volcanoes. Quaternary Tectonics. Fundamental research focusing on Late Quaternary history (roughly the past 500,000 years), including tectonic geology and geomorphology, paleoseismology, neotectonics, and geodesy, presents an unusual opportunity to catalog and understand ongoing active tectonic processes. This understanding could become the basis for assessing the potential to predict tectonic activities and other changes up to several thousand years in the future. Predicting or forecasting the future is essential for designing ways to minimize the disastrous effects of earthquakes and volcanic eruptions and for selecting the most stable sites for long-term disposal of hazardous and radioactive wastes. Soil Cohesion. Improved methods of densifying or increasing cohesion of soil materials can increase the shear strength of susceptible soils and thereby eliminate potential liquefaction during earthquake and other cyclic vibrational loadings. Volume-Changing Soils. Much of the western United States is dotted with patches of land that are susceptible to significant changes in volume, activated by slight increases in moisture content. The changes, whether collapse or swelling, are sufficient to bring about structural damages to engineering works. Such damage is diffuse and rarely life threatening but amounts to as much as $2 billion per year. State coverage maps of areas with inherently weak soil fabrics or certain clay minerals could raise public awareness to the point that such damage could be nearly eliminated. Landslide Susceptibility Maps. Maps for landslide detection and evaluation have been formulated by application of new concepts such as geographic information systems, a digital system of mapping. We can expect major strides in decision making as applied to human activities around landslides. Landslide Prevention. Alternative methods of preventing landslides and of stabilizing active landslides are a prime area for research, for the purpose of reclaiming otherwise unusable land for high-value human use. Geomorphic Hazards Age-Dating Techniques. The greatest research need is for data management and physical models to quantify rates of active tectonic processes. Public policy decisions, for example, need such data arrays to determine what levels of earth hazard risks are acceptable. Decisions rest largely on evaluations of the rates (and the variability of the rates) of processes, the frequency of events, and the prediction of when hazards might become critical. Real-Time Geology. Computers and electromechanical instrumentation now make possible the monitoring and instantaneous analysis of geological processes that occur very rapidly, and this capability leads to exciting new possibilities for prediction and forecasting. In addition, the documentation and understanding of rapid geological processes are an entirely new dimension for earth scientists to explore.
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Solid-Earth Sciences and Society Systems Approach. A systems approach to geomorphic and engineering problems must be developed if serious and unforeseen consequences of human actions are to be avoided. The geomorphologist has the long-term perspective of landform change that is needed in meeting and dealing with many engineering and land management programs, and familiarity with the effects of time, landform evolution, and thresholds of instability are critical for prediction of future events and landform responses. Extreme Events. The effect of extreme events in modifying or conditioning the landscape is a developing field. For example, rainfall-runoff floods and floods from natural-dam failures may be accompanied by massive erosion and sedimentation. A related field is the interdependency of events, as illustrated by the 1980 eruption of Mount St. Helens. The eruption and huge landslide formed several large lakes, and groundwater disruption became the cause of new instability of the natural dam. Sediment eroded from the debris avalanche in the Toutle River valley continues to plague downstream channel capacity, fish habitat, and water quality. A huge and expensive dam will be required to mitigate this problem. Land-Use and Urban Planning Geographic Information Systems (GISs). The way in which solid-earth science information is used with other kinds of societally important information requires the information-layering capability that is the essence of GISs. The solid-earth scientist has an important role in establishing appropriate standards for the way in which specialized data are used in GISs, as well as to ensure that such information is up to date and of high-quality. Land Use and Reuse. The effects of geological constraints on land use and reuse will continue to be a significant issue for the future. Society must become a deferential part of the environment, not its master; human actions have profound and far-reaching impacts on the rest of the earth system. Hazard-Interaction Problems. A shift in perspective is needed from the incrementalism of individual site-specific hazards to the broader systems approach, dealing with single or multiple hazards common to broader physiographic regions. Increasingly, earth scientists, civil engineers, land-use planners, and public officials are noting the existence of interactive natural hazards that occur simultaneously or in sequence and that produce synergistic cumulative impacts that differ from those of their separately acting component hazards. Detection of Neotectonic Features. Identifying these features, which are key data links to a better understanding of a long-term seismicity, requires geological mapping of each seismically active region of the country. Such assessments are critical to the siting and design of safe facilities that are of critical-performance nature or serve housing-dependent populations (hospitals and schools) and to the establishment of realistic building codes. Soil Processes and Microbiology. New theories of the relations between microbiology and soil processes, which are important because food production is tied to soil science, can be established with new chemical and instrumental techniques. Large-scale remote sensing can monitor growth patterns on different soil types and enhance land management to preserve our precious soil bank. Rock-Bearing Capacity. Research on the bearing capacity of the weathered rock zone together with better definition, identification, and classification of strong soil/weak rock could save considerable money, both in design and construction of buildings. Urban Planning and Underground Space. If we are to unclog our cities with the limited financial resources at hand, planning must start to take into account utilization of the subsurface. The use of underground space is an undeniable necessity of the future, to be undertaken as population centers are redeveloped. There is only so much room on the land, and the prime space must be used for human habitation. With the predicted increase in usage of underground space, new technologies for characterization and sealing of rock fractures against groundwater inflow will become a necessity. Geophysical Subsurface Exploration. Improved geophysical techniques for subsurface exploration and computer-based methods for data processing offer new opportunities to predict and control human-induced land subsidence. Techniques such as ground-penetrating radar are now commonly used to detect underground cavities, such as caverns and abandoned mines at shallow depths, and seismic tomography is being experimented with to evaluate the conditions of pillars in abandoned mines of such urban areas as Pittsburgh, Birmingham, and Kansas City. Underground Void Detection. The detection of underground voids by indirect methods needs to be greatly improved. Many subsidence problems are associated with either carbonate-solution caverns or abandoned underground mines, and it is usually
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Solid-Earth Sciences and Society impractical to drill out suspect areas. Prediction of limestone sinkhole collapse will remain elusive until the triggering mechanisms are better understood. Objective D: To Minimize Perturbations from and Adjust to Global and Environmental Change Mineral Products and Health Interdisciplinary Earth Science/Materials/Medical Research. Interdisciplinary research in these apparently diverse fields can provide a substantial opportunity to address major societal issues regarding health. This involves research into and public education about acceptable levels of risk in relationship to costs. Three examples are (1) the "asbestos hazard" where the relation between crystal size, shape, structure, and composition and chemical/ biological interaction is particularly important; (2) the radon concern; and (3) the presence and hazard to humans of trace elements present in the environment, especially if they may interact. Contamination of Aquifers Radioactive Waste Isolation. To ensure the isolation of radioactive waste, which has been designated by the Congress to deep disposal only, hydrologic research on sedimentary and volcanic deposits plays an important role. Sedimentary deposits contain aquifers, which are the single most important reservoir for fresh water. Groundwater Protection. Protecting groundwater quality requires monitoring and sampling, such as vadose zone sampling, sampling of volatile organic components in groundwater, and sampling volatile organic components that might affect employee safety. Improved methods for testing field permeability and in situ methods of measuring the physical and chemical properties of soil and rock are needed. Organic Chemistry Control. Biological control of organic chemical reactions, especially in groundwater, is a rich area for research—research with a high potential monetary payoff in terms of current and ongoing expenditures for waste site remediation. Chemical reactions involving the fate of in situ organic compounds are controlled by soil microorganisms, and understanding the kinetics of such reactions poses a scientific challenge. Introducing an organism that produces a benign byproduct may be the cheapest way to remediate some forms of groundwater contamination. In many instances groundwater moves so slowly that colonies of microorganisms can actually move with the plume of contamination. Waste Management and Environmental Change Waste Management: Landfills. The earth science community is equipped to develop management expertise for those materials that must be consigned to land burial. Waste Management Geochemistry. A new field of geochemistry of waste management can be produced by recycling metals from waste. Hazardous Waste Cleanup. In situ cleanup of uncontrolled hazardous waste sites vitally needs attention. The importance of fracture sealing of radioactive waste repositories in the subsurface cannot be overemphasized. Future generations should not be left with isolated pockets of hazardous material whose limits will undoubtedly become unknown with time. Waste Disposal from Mining Operations. The problems with disposal of the waste from mining, milling, and in situ leaching need much greater emphasis, both for better understanding and, where possible, for mitigation of the potential adverse effects of exploiting and utilizing energy resources. Research and technological development are needed. Also, methods for site selection, characterization, and design of proposed repository sites for radioactive wastes have still not been developed. Coal Mining and the Environment. The environmental impact of mining coals and their environmental acceptability as fuel are the most important aspects of coal research. Every stage of coal development, from exploration to consumption, has potential environmental impacts. Mine safety and mine site rehabilitation will also require research. Nuclear-Energy-Related Wastes. Disposal of spoil waste at mine sites and of spent reactor material is the most important research area for nuclear energy. Recent concern about atmospheric carbon dioxide buildup, as well as about the increase in acid rain resulting partially from coal usage, may lead to a reevaluation of policies relating to nuclear power. Global Change. The solid-earth scientist is the custodian of the past record of global change, and the research areas recommended in Chapter 3 are related to that record. Here the emphasis is on the most recent past. Past Global Change. The record in ice cores, tree rings, deep-sea cores, lake-bed deposits, and surface features like sand dunes and glacial deposits is generally the most complete record of the recent
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Solid-Earth Sciences and Society past, but other environments preserve some information. Integrated pictures of what the world was like at specific times—for example 5,000, 10,000, or 20,000 years ago—such as those compiled by the CLIMAP and COHMAP consortia can help in understanding how the world has changed. They can also be used to test the usefulness of the models constructed by geophysical fluid dynamicists. Abrupt and Catastrophic Changes in the Past. Episodes of sudden environmental change have been identified from times as recent as 10,000 years ago to 66-million-years ago and more. If we can work out what happened under the peculiar circumstances of those times, it may help in understanding the likely effects of the current changes. Solid-Earth Processes in Global Change. We need a better understanding of how sea level might be changing at present and the effects of volcanism, both above and below sea level, on the global environment. The volume of the ice sheets should be monitored on the decadal scale, and changes in permafrost areas should be observed. Monitoring global change at the surface from space, using the ongoing high-spatial-resolution imagery of Landsat and SPOT-type instruments, is essential for seeing what is happening in such environments as the Sahel, central Asia, and the Altiplano. Present-Day Geochemical/Geophysical Data Base. A global data base of present-day geochemical and geophysical measurements needs to be established for direct detection of future changes. Such data are lacking for remote and underdeveloped regions of the world. Climatic Effects of Volcanic Emissions. The effect on climate modification of volcanic emissions, and their interactions with the atmosphere and hydrosphere, can be better understood from global monitoring of volcanism. BIBLIOGRAPHY NRC Reports NRC (1978). 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Representative terms from entire chapter: