Solid-Earth Sciences and Society (1993) / Chapter Skim
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5 Hazards, Land Use, and Environmental Change
5 Hazards, Land Use, and Environmental Change
Pages 185-232
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From page 185... ...
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.
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From page 186... ...
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.
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From page 187... ...
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.
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From page 188... ...
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.
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From page 189... ...
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 hilIsIope 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.
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From page 190... ...
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 anal F O R O F MOVEMENT _ _ I SOLID-EARTH SCIENCES AND SOCIETY TYP E OF MOVEM EAT FALLING SLIDING | FLOWING FOR M OF MOVE MENT ROCKFALL I i= - 1 1 1 \ ~ i\\ ale '- ' ~ SOILFALL I B LO C K LATE RAL \ SLIDE SPREAD OF _ ~ LOC K5 ~ \ "A 1 ' ' _ -j'\~\ '-'a ~ I ~ I I , (~ ~\ lij 1 D E B RIS FLOW, SOI LFLOW, E ARTH FLOW, M U D F L O W 'I SOIL~!
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From page 191... ...
Debris Flows In the 1970s, landslides all categories of gravityrelated slope failures in earth materials-caused nearly 600 deaths per year worldwide. About 90 percent of the deaths occurred in the circum-Pacific countries.
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From page 192... ...
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.
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From page 193... ...
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 elects 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.
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From page 194... ...
. 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.
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From page 195... ...
But earth scientists do not know what to elect with additional perturbation from a changing greenhouse effect. Will the predicted temperature increase cause a decrease in precipitation, as occurred in midAmerica during the summer of 1988?
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From page 196... ...
Some of the most frightening floods descend on mountain settlements when their watersheds receive cloudburst rain, and flash floods completely scour out valleys. In canyons of the mountainous western United States, warning signs read, "In case of flash flood, climb straight up." In the United States, rainstorms and their accompanying flooding and debris flows accounted for 337 of the 531 federally declared disaster areas from 1965 to 1985.
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From page 197... ...
These brackish tidal waters are nursery grounds for many marine organisms as well as invitations for the establishment of human populations because of access to those nursery grounds, to transportation routes, and to freshwater sources just up river. Many, if not most, of the major estuaries of the country have become con taminated by natural or human-introduced pollutants.
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From page 198... ...
Administrators cannot elect citizens to abandon their daily lives for anything but imminent danger. Therefore, earth scientists have an obligation to acquire relevant data and pursue research aimed at reliable depiction of an earthquake threat.
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From page 199... ...
73. provides an accurate and useful understanding of an earthquake's seismic hazard parameters, the nature of the earthquake source, the maximum size of the resulting seismic waves, the qualitative characteristics of those seismic waves, and the potential effect along the surface in response to the wave's energy.
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From page 200... ...
But the possibility of powerful earthquakes occurring along this zone, which includes the cities of Vancouver, Seattle, and Portland, is suggested on the basis of its plate tectonic setting as well as neotectonic geological studies that indicate the oc { Slip Rate Recurrence Interval Elapsed Time Displacement/Event Fau It Geometry LONG-TERM EARTHQUAKE POTENTIAL · Hazard Model Probab i l ity of Occu rrence R ECU R R ENCE MODE LS currence of major subduction-zone earthquakes here within the recent prehistorical past. Earthquakes comparable in size to the 1964 Alaskan earthquake which devastated Anchorage may well occur along this coastline of the Pacific Northwest Intraplate earthquakes can pose a threat comparable to plate boundary events, as shown by the three very large earthquakes that rocked the New Madrid, Missouri, region in late 1811 and early 1812.
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From page 201... ...
Clearly, these historical events can indicate earthquake sources that might not otherwise be evident. The extensive historical catalogs may also provide indications of short-term fluctuations in the locations, sizes, and rates of earthquake activity that have not left evidence in the much longer geological record.
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From page 202... ...
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From page 203... ...
Earth scientists have also improved their ability to use mathematical inversion techniques. Inversion analyzes the effects to gain knowledge about the nature of the cause.
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From page 205... ...
Powerful examples of the application of inversion techniques can be found in the studies of recent earthquakes at Imperial Valley and Coalinga, California, and the earthquake at Borah Peak, Idaho. During the past 20 years efforts to obtain records of strong ground motion have increased, and the data bank has grown with each successive earthquake.
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From page 206... ...
A fundamental goal of seismic hazard research and risk assessment is accurate prediction of poten tially damaging ground motion. Seismic hazard is assessed using deterministic and probabilistic statis tical analyses, and a dynamical systems approach is seismic risk in a socially useful manner.
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From page 207... ...
For example, a decade ago the prospect for the generation of great earthquakes in the Cascadia subduction zone Blithe Pacific Northwest coast was 207 .~..~. FIGURE 5.15 Sand boils resulting from liquefaction during the 1989 Loma Prieta earthquake near Santa Cruz, California.
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From page 208... ...
The intensity distribution of earthquake ground shaking often exhibits a very irregular spatial pattern because of variations in the crustal structure near the epicenter, in site response, and in the force mechanisms such as strike-slip, along the San Andreas Fault, or dip-slip, in western Mexico. When seismic networks are supplemented by portable instruments, generic path effects and site responses in an earthquake-prone region can be defined.
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From page 209... ...
Closely related to the tsunami hazard is seiching, or the oscillation of closed and partially open bodies of water caused by long-period surface waves, which are often produced by the same large earthquakes that generate significant tsunamis. For example, the 1964 Alaskan earthquake caused waves as high as 2 m in bays and channels along the Gulf of Mexico, with sizes and shapes suitable for resonating with the wavelength of the arriving longperiod seismic energy.
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From page 210... ...
Known techniques must be expanded, and new ones developed, for assessing volcanic hazards and monitoring active and potentially active volcanoes. A high priority must be given to public education; as with earthquake and tsunami warnings, a fine line must be followed between offering correct information about probability and risk and diluting the importance of a warning by false or misunderstoodalarms.
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From page 211... ...
More precise methods are needed to distinguish between shallow intrusions of molten rock that will erupt to the surface and those that will not. In addition, scientists need to learn how to communicate the uncertainties involved in forecasting eruptions to the governing officials and the public at risk near potentially active volcanoes.
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From page 212... ...
They might not necessarily be directly associated with a volcanic eruption but can be triggered by a nearby earthquake that might destabilize the glaciers on the volcanic edifice Mount Rainier currently has over 4 km3 of perennial ice on its peaks; such mudflows are poised to occur again. Because of the potential mudflow and volcanic hazards at Mount Rainier, it has been designated as a "Decade Volcano" within the context of the International Decade of Natural Disaster Reduction.
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From page 213... ...
Only about 10 percent of the world's 1,300 potentially active volcanoes have been geologically mapped to assess their past eruptive habits. This leaves 90 percent yet to be studied.
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From page 214... ...
Earth scientists have the opportunity, perhaps the duty, to provide that information. Significant issues for the future will involve as sessments of possible land use, concentrating on reuse, as affected by geological constraints.
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From page 215... ...
But the geological constraints themselves are becoming more evident, as is the need to analyze them more thoroughly not only for their effects on redevelopment projects but also for their effects on the physical stability of existing buildings and potentially large cost overruns associated with unexpected geological conditions, especially weak earth materials and large inflows of groundwater. Engineered Structures Geological site interpretations are needed for all forms of engineered construction, such as dams, nuclear power plants, hydropower plants, pumping plants, factories, sewers, canals, levees, high-rise buildings, harbors, locks, highways, bridges, tunnels, airports, and port facilities.
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From page 216... ...
Use of Earth Materials Earth materials are linked to land use and environmental management in many ways. Engineered works utilize earth materials both as the foundations, soils or underlying rock, and as raw material ~ .
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From page 217... ...
And large underground caverns, often left by mining enterprises, are increasingly being used to store petroleum and natural gas as well as radioactive waste. Greater Kansas City is now a world leader in conversion of mined underground space to lowenergy, secure commodity storage.
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From page 218... ...
A ban on the use of any serpentinite rock of which noncarcinogenic chrysotile is one type-for commercial purposes is now pending in California; at the same time, serpentine is California's state rock. It should perhaps be noted that in 1969 the common mineral quartz was placed on California's list of carcinogens because tumors were generated in SOLID-EARTH SCIENCES AND SOCIETY rats breathing quartz dust, and the Internationa Agency for Research on Cancer has since designated quartz as a carcinogen.
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From page 219... ...
The role of the earth science community is probably limited to urging more people to voluntarily monitor their household radon levels and to pointing out that, in the past, too much emphasis was placed on soil radium concentrations and too little on soil permeability. High-radium soils may not lead to radon hazards in the home, and low-radium soils do not guarantee safety.
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From page 220... ...
Earth scientists need to work with agricultural scientists to understand the complex processes of soil degradation and soil erosion. Waste Management Advanced societies generate huge masses of diverse wastes that need to be minimized and then isolated in environmentally acceptable ways with a view toward possible reuse.
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From page 221... ...
The existing rules are inappropriate and cannot be expected to produce a successful outcome. Conversion of radioactive wastes to ceramics, which are then encased in additional outer containers of ceramic material, has been shown to be a satisfactory way of isolating waste and in many cases may be sufficient.
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From page 222... ...
war ~ SOLID-EARTH SCIENCES AND SOCIETY 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, mak ing a large proportion of analyses suspect.
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From page 223... ...
Hydrologic research was the topic of a recent full-scale assessment by the NRC. Solidearth scientists are closely involved in hydrology, and their research dominates both surface drainage and underground water.
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From page 224... ...
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.
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From page 225... ...
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.
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From page 226... ...
. 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.
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From page 227... ...
Mitigate Geological Hazards Earthquakes, Volcanoes, A B Landslides T · Soil processes and microbiology · Seismic safety of reservoirs · Precursory phenomena and volcanic eruptions · Volume-changing soils · 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 D Minimize Perturbations from Global and Environmental Change Assess, Mitigate, Remediate · 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.
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From page 228... ...
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.
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From page 229... ...
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 229 cumulative impacts that differ from those of their separately acting component hazards. · Detection of Neotectonic Features.
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From page 230... ...
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.
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From page 231... ...
NRC (1989~. Irrigation-Induced Water Quality Problems, Water Science and Technology Board, National Research Council, National Academy Press, Washington, D.C., 157 pp.
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From page 232... ...
, Board on Radioactive Waste Management, National SOLID-EARTH SCIENCES AND SOCIETY Research Council, National Academy Press, Washington, D.C., 231 pp.
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