Solid-Earth Sciences and Society (1993) / Chapter Skim
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1 Global Overview
1 Global Overview
Pages 13-46
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From page 13... ...
Research ranges from the atomic scale of the scanning-tunneling microscope and ion microprobe to the global scale of worldwide seismic networks and images produced from data gathered by orbiting satellites. Earth scientists are constructing a comprehensive picture of the Earth, one that interrelates the physical, chemical, geological, and biological processes that characterize the planet and its history (Plate I)
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From page 14... ...
One of the triumphs of twentieth-century science and technology has been the worldwide identification and extraction of energy and mineral resources, an activity that has brought an increased standard of living to an expanding human population. The geological sciences have demonstrated ways of maintaining water quantity and quality, disposing of wastes safely, and securing human structures and facilities against natural hazards.
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From page 15... ...
For instance, numerical computer simulations have been devised for mantle convection, for the evolution of sedimentary basins, for surface processes such as erosion, for fluid flow, and for rupture processes in earthquakes. At the same time, solid-earth scientists are relying on increasingly sophisticated instrumentation to expand and to keep up with the data needed for future discoveries and for models that assess and predict earth processes.
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From page 16... ...
THE EARTH AND ITS COMPONENTS Development of the geological sciences has been marked by two seemingly contradictory but in fact complementary trends Earth scientists have become ever more aware of the great complexity of the Earth and its constituents; certain individual minerals, for example, are among the most complex inorganic substances known At the same time, earth scientists are uncovering the principles that lie behind the Earth's bewildering diversity- unifying concepts that bring coherence to a welter of seemingly unrelated observations One way to approach the planet's apparent complexity is to look upon the Earth as a system of interacting components Viewed in its entirety, the earth system is driven by energy from two sources: (1) inside the Earth from primordial energy remaining from accretion and by radioactive decay of elements and (2)
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From page 17... ...
In this way geologists have been able to chart past changes in temperature, sea level, atmospheric and oceanic composition, volcanism, plate tectonics, the evolu tion of life, the Earth's magnetic field, sedimentation rates, and glaciation (Plate 2~. Earth scientists study this record to learn how the components of the Earth behaved and interacted in the past, to understand how they interact now, and to predict how they will interact in the future.
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From page 18... ...
UNIFYING FORCES IN THE GEOLOGICAL SCIENCES Many advances have simultaneously contributed to a general unification of the geological sciences, but three in particular stand out: the plate tectonic revolution, the enhanced ability to produce images of both the surface and the interior, and the increasing recognition of humanity as a geological agent. Plate Tectonics In the 1960s the geological sciences experienced a conceptual revolution that continues to affect the field today.
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From page 19... ...
Global positioning systems use satellites to measure the location of receivers on the Earth to an accuracy of a few centimeters. This technique has enabled earth scientists to measure the relative velocities of the plates, determine how the velocities change where plates come together, and assess the rigidity of plate interiors.
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From page 20... ...
The geological sciences offer information that will be invaluable in evaluating trade-offs and in balancing competing demands. GOALS OF THE EARTH SCIENCES: RESEARCH FRAMEWORK There are two fundamental reasons for pursuing the earth sciences.
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From page 21... ...
The concept of plate tectonics provides a grand example of the planet as an integrated system, 21 every part functioning to some degree separately but ultimately dependent on all others. New probes of the interior have reinforced the notion of an internal engine that drives geological processes.
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From page 22... ...
Important investigations of biogeochemical cycles consider the interaction between solid earth and fluid envelopes. A major factor in changing the paleoenvironments that influence biological evolution is plate tectonics, which is associated directly with mantle convection and lithosphere dynamics.
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From page 23... ...
Connections between objectives and research areas within the Research Framework may help to guide some redistribution of effort. The detailed review of the priority themes that follows, with consideration of the personnel,
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From page 24... ...
PRIORITY THEMES: RESEARCH AREAS The priority themes can be related to form together in a continuous story. The Earth operates as a thermal engine, driven by primordial heat from accretion, by the continuing decay of radioactive material dispersed through the interior, and by energy generated by the gravitational accumulation of the inner core from the outer core.
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From page 25... ...
New approaches to the study of global geochemical cycles contribute to these reconstructions of largescale environmental change. Researchers are only beginning to appreciate how much life-supporting oxygen and heat-trapping carbon dioxide have fluctuated.
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From page 26... ...
Priority Theme A-II: Global Geochemical and Biogeochemical Cycles Geochemical cycles the cyclic movement of chemical elements, nuclides, and compounds through the great reservoirs ofthe Earth constituted by the biosphere, atmosphere, oceans, sediments, crust, mantle, and core have received recent attention because of advances in analytical techniques, data-handling, and modeling capabilities. The reservoirs may be very large, on the scale of the whole Earth, sequestering elements for a billion years, or they may be as small as a backyard, exchanging material with the surroundings over a few days.
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From page 27... ...
Humanly altered biogeochemical cycles modify the composition of the atmosphere. For example, the addition of carbon dioxide and sulfur-containing gases to the atmosphere by the burning of coal and oil results in greenhouse warming and acid rain.
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From page 28... ...
The ultimate goal of studies of geochemical cycling is reconstruction of the historical development of the Earth and its environment Geochemical cycling is a unifying concept that brings together results from studies of various earth features, including mantle evolution, global tectonics, rockwater interaction, paleoclimatology, and organic evolution Compilation of geological history and study of modern processes and their rates permit mathematical modeling of these cycles These models provide a means of evaluating the quantitative significance of specific earth processes during selected intervals of the past Such modeling can provide a basis for making future predictions Priority Theme A-III: Fluids in ant! on the Earth Fluids dominate the redistribution of mass and energy through the earth system Their role is prominent in the generation, migration, and eruption of magmas; in the chemical alteration of masses of rock during metamorphism and mountain building; in the mechanical transport of material on the surface; in the formation of ore deposits; and in the migration and entrapment of of!
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From page 29... ...
Priority Theme A-IV: Crustal Dynamics: Ocean and Continents The notion of terra firma is deeply ingrained in the human subconscious, and yet testimonials to the Earth's vigorous dynamics litter the landscape. An abundance of diverse landforms and surface environments, from spectacular mountains to desert valleys, from rocky coastlines to verdant tropical islands, demonstrate ongoing adjustments to the planet's surface.
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From page 30... ...
In contrast, the continental crustal areas are more complex; their growth patterns extend over 4 billion years. Earth scientists agree that for a short period about 250 million years ago, nearly all the continental material was consolidated into a great landmass, the supercontinent Pangea (Figure 1.8~.
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From page 31... ...
The second examines isotopic geochronology and thermobarometric pressure values available from radial growth patterns of minerals and from their inclusions. These new techniques, which combine mineralogy with geochemistry, yield direct estimates for the rates of geological processes associated with mountain building.
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From page 32... ...
In this case, human intervention is disrupting the balance of crustal dynamics. Priority Theme A-V: Core and Mantle Dynamics The internal structure of the Earth has been studied in recent years from several very different perspectives: seismic waves generated by both earthquakes and explosions have shown how the structure varies, geochemical analysis of mantlederived rock reveals variations in the mantle's composition, and meteorites that are fragments of planetary objects supply information about other mantles, similar to Earth's.
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From page 33... ...
Geological Survey Water Supply Paper 2275.
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From page 34... ...
The excitement and importance of this challenge are enhanced by the immediate benefits to society to be derived from that understanding. Comprehension of earth system processes applies directly to the specific objectives of maintaining resource supplies; preventing damage caused by geological disasters; and assessing, mitigating, and remediating effects of global environmental change.
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From page 35... ...
The Earth s landscapes consist of nested drainage basins on horizontal scales ranging from that of a freshet network on a hillside to the vast Amazon Basin. Relating these networks and their evolution to the sedimentary basins that receive eroded material remains a major focus of earth science.
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From page 36... ...
Priority Theme C: Preventing Damage from Geological Hazards Human society is a part of the biosphere, which exists within the zone where the solid earth interacts with its fluid envelopes. This zone is perched between the two engines of mantle convection and solar energy that drive geological processes.
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From page 37... ...
Priority Theme D: Assessing, Mitigating, and Remediating Effects of Environmental and GIobal Change The environment changes progressively as continents drift, ocean basins open and close, climates fluctuate, and ocean currents adjust accordingly. Geological evidence demonstrates that rates of environmental change vary and that some catastrophic events cause abrupt changes.
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From page 38... ...
The conventional cycles of biogeochemical processes concentrate elements into living creatures and into ore deposits and other geological features. Now these processes follow new paths of chemical migrations and concentrations, forming compounds deliberately generated by manufacturing and inadvertently generated by the disposal of materials.
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From page 39... ...
Considering the overall distribution of federal support across the Priority Themes in the Research Framework, there do not appear to be significant gaps, which indicates that the existing national research structure is working reasonably well. Many of the priority themes are already well eseablished.
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From page 40... ...
The industry-supported Petroleum Research Fund of the American Chemical Society has played an important role for decades A wide variety of university programs have been encouraged through these means, ranging from basic research in petrology, paleontology, and sedimentology to technologies for reservoir characterization, enhanced oil recovery, and seismic signal processing. Petroleum industry support of environmental research is growing.
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From page 41... ...
The instruments used by laboratory earth scientists sel dom cost as much as $1 million, although some essential data can only be acquired using expensive facilities such as accelerators, mass spectrometers, or synchotrons. Success in obtaining some of the more expensive instruments often comes from collaboration, con 41 ~ / i \ ~ .~\!
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From page 42... ...
Numerical computer simulations have been devised for mantle convection, the evolution of sedimentary basins, the concentration of oil and gas resources, climate change, and surface processes such as erosion, fluid flow, and rupturing of the crust in earthquakes. These models are tools that have been used to allow scientists to rapidly test hypotheses about earth processes.
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From page 43... ...
Digital earth science data should be available at an international level to broaden the research base for all scientists. EDUCATION AND EMPLOYMENT There is a national crisis in science education.
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From page 44... ...
Introductory geology courses, which represent the only exposure that most students have to the earth sciences, should be stimulating and challenging Comprehensive courses in earth system science, emphasizing interrelationships and feedback processes, as well as the involvement of the biosphere in geochemical processes, would appeal not only to life and earth scientists but also to a wider range of curious students Professional programs must increase offerings in emerging fields and might consider phasing out less useful requirements Growth in both employment and research opportunities can be expected in such areas as hydrology, land use, engineering geology, environmental and urban geology, and waste disposal. The interests of earth science and engineering departments converge in these fields, and opportunities to link the two should be explored.
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From page 45... ...
Minimize Global and Environmental Change Assess, Mitigate, Remediate Chapter 3 Chapter 4 Chapter 5 II. Global Geochemical and Biogeochemical Cycles III.
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From page 46... ...
Past environmental changes and their effects on life can be determined from the study of sedimentary rocks, which contain the record of ancient environments, including information about the composition of the atmosphere and oceans through time. Studies of continental, oceanic, and atmospheric processes have been revitalized by the integration of this compositional information with interpretations of plate tectonic movement and the resulting changes in distribution of continents and ocean basins.
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