Basic Research Opportunities in Earth Science (2001) / Chapter Skim
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2. Science Opportunities
2. Science Opportunities
Pages 35-88
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From page 35... ...
The committee emphasizes that this is not intended to be a comprehensive list of exciting areas in Earth science, or to represent the full variety of research currently sponsored by the Earth Science Division (EAR) of the National Science Foundation (NSF)
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The historical record of direct observations is far too short to capture the full range of possible behaviors in the Critical Zone, and extensive use of the geological record becomes necessary. For instance, biogeochemical cycles are studied over decades to centuries through high-precision geochemical analysis of ice and sediment cores and marine organisms, while the geologic forcing factors (e.g., volcanism, topography are constrained through the analysis of sedimentary and volcanic rocks deposited over millions of years.
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From page 38... ...
The upper boundary of the Cntical Zone includes the land surface and its canopy of lakes, rivers, and vegetation, as well as its shorelines and shallow marine environments. On land, the shallower part is the vadose zone, in which unconsolidated Earth materials are intermixed with soil, air, and water.
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From page 40... ...
Such models are being constrained by imaging and analytical measurements developed over the past few years and will provide new insight into the physical, biological, and chemical influences on water quality and availability. The Land-Ocean Interface New technology is yielding vastly improved insights to the nature and dynamics of coastal sedimentary environments.2 For example, scanning airborne lasers are measuring seafloor bathymetry and topography of coastal areas with unprecedented accuracy and spatial coverage allowing assessment and understanding of coastal change in ways that were not possible only a 2Coastal Sedimentary Geology Research: A Critical National and Global Priority, results of a workshop held in Honolulu, Hawaii, November 9-12, 1999.
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From page 42... ...
A good example, based on both careful geological field work and geochemical and isotopic observations, is the recent suggestion that the Earn went through a series of global glacial events ("snowball Earth") about 750 million to 580 million years ago.
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and spectroscopic tools that probe soil materials to the atomic scale; and new information technologies, which permit the manipulation of large data sets and a variety of numerical simulations, from ab initio models of atomic and molecular interactions to global ocean and atrnosphenc circulation and mountain belt evolution. These technological advances have set up opportunities for novel cross-disciplinary activities.
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From page 44... ...
This theme permeates the discussion of many other aspects of Earth science in this report, but, in the case of the Critical Zone, it presents some special challenges, in part because of the sheer number of the disciplines and the diversity of their approaches, but more profoundly because of He spatial scales intrinsic to the scientific issues. Although Critical Zone processes often involve the global aspects of atmospheric and oceanic transport, many of the most intense interactions occur in relatively localized regions of the solid Earth for example, over dimensions less than the characteristic horizontal variations in topography and near-surface geology (tens to hundreds of kilometers)
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.. .~ ~ 45 rapidly in the study of global-scale geosystems, which manifest a more obvious set of unifying concepts, diagnostic behaviors, and simple symmetnes—tor example, the dlpolar magnetic field (core dynamo)
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From page 46... ...
Geobiological research results bear directly on a wide array of important scientific and societal issues, including the nature of the Critical Zone, the stability and resilience of ecosystems under stress, and the origin and evolution of life itself. Geobiological processes operate over a wide spectrum of temporal and spatial scales from small-scale, rapid exhalation of O2 by cyanobacter~a, to cycling of carbon through communities of marine phytoplankton and rain forests, to restructuring of regional and global ecosystems in the wake of major extinction events, to shifts in reef composition in response to slowly changing rates of seafloor spreading (Figure 2.4~.
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Hardie, Hypercalcification: Paleontology links plate tectonics and geochemistry to sedimentology, GSA Today, v.
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New insights into the roles of microbial metabolism, organic chelators, and sediment-irrigating and -adverting plants and animals in processes such as mineral dissolution, mineral precipitation, soil formation, and sedimentary diagenesis are opening the way for more detailed understanding of Critical Zone processes both modern and ancient.
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Correlating genomic events with the geological record remains a significant challenge. Where the geologic record indicates considerable diversity within a group, the line depicting the lineage has been widened (yellow and blue wedges)
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and the midPaleozoic invasion of land. Geological and molecular data can also be used to calibrate molecular clocks based on differences between the DNA of living species; these clocks can then be applied to lineages otherwise lacking a rich fossil record.
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FIGURE 2.6 Phylogeny of selected animal phyla, showing the stratigraphic extent of their fossil records (body fossils only)
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t4~ am- ^: , ~ > ~~ it- ~ —~~ -f :__.' ~ elf ~ ~ ~ ~ ' ' ~ ~ 2 /\~ 3 Avalonia 2 1 / o ~ Baltoscandia South America FIGURE 2.7 Pattems of diversification of Ordovician bivalve molluscs around the world. As with other marine organisms, the pattern varies by geographic location, indicating that the Ordovician radiation (the largest diversification of animal genera seen in the fossil record)
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From page 53... ...
For example, the Late Paleocene Thermal Maximum, possibly enhanced by a massive release of methane hydrates at ocean margins, produced a surprisingly mild extinction, and in some environments even promoted diversification, outside of the deep sea. New Tools and Capabilities New and improved biological, chemical, geological, and paleontological methods hold enormous potential for geobiological research.
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From page 54... ...
Fundamental new knowledge at the interface of the biological and Earth sciences is anticipated in the following broad areas: · the interrelationship among organisms, biological processes, and the fundamental physical and chemical properties of the Critical Zone; · the extent to which geological processes, such as weathering and mineral precipitation, are mediated by biological processes, and the mechanisms by which this mediation occurs; · the ways in which biogeochemical cycles operate and are controlled or modulated by physical, chemical, and biological processes; · the role of physical factors, including rare events, in structuring and changing the composition and organization of biological communities;
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Recent Advances Earth and planetary materials research is based on an atomistic approach—establishing properties at the molecular level in order to understand materials and processes at much larger scales. It has involved the development of major new research tools.
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. The observations represent the time required for seismic waves to travel through the inner core, showing that travel times (hence wave velocities)
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In particular, the details of fluid-mineral interactions determine the degree, rate, and paths with which surface and underground contaminants migrate and the means by which such effects can be mitigated. · Land resources are composed of soils with active colloidal fractions dominated by organic-mineral nanophases whose surfaces control the chemical speciation and fate, mobility, bioavailability, reactivity, transport, See also Microscopic to Macroscopic: Opportunities in Mineral and Rock Physics and Chemistry, results of a workshop held in Scottsdale, Arizona, May 28-30, 1999.
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From page 59... ...
Science Opportunities The momentum associated with recent discoveries, improved facilities, and new collaborations between disciplines offers a glimpse into future possibilities. The coming decade will see the emergence of major opportunities for research on Earth and planetary materials.
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Casey, and M Karlsson, Bonding and reactivity at oxide mineral surfaces from model aqueous complexes, Nature, v.
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Natural laboratories have enormous potential as facilities where data sets with appropriate detail and precision can be collected systematically over the long term under natural conditions. For example, the San Andreas Fault Observatory at Depth (SAFOD)
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Properly interpreted, continental geology yields information about these processes and about the large-scale dynamics that control mantle convection, planetary differentiation, plate motions, and climate throughout Earth history. Today, many fundamental and controversial ideas about the continents await testing through the integration of field geology and geomorphology with new technologies in geochemistry, geophysics, and geodesy.
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From page 63... ...
These techniques have been applied to samples brought up from depths of hundreds of kilometers in continental volcanic eruptions, allowing geochemists to constrain the history of even the deepest parts of the continental lithosphere. Based on comparisons with the results of high-pressure mineral physics experiments, some of these rocks appear to have come from as deep as the lower mantle, providing unique data on large-scale dynamical processes of the Earth's interior.
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From page 64... ...
In the northern portion of the diagram the zone of active strain between the Pacific plate and North America is several hundred kilometers in width, while in the southern portion of the diagram, most of the strain is localized within a zone 50 km wide and occurs on or near the San Andreas Fault. Companson of actively accumulating deformation obtained from geodetic measurements yields important insights into seismic risk.
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From page 66... ...
Surface Processes, Climate, and Tectonics What were once thought to be one-way forcing functions are now recognized to act in both directions, with feedback coupling continental tectonics, erosion processes, climate, and the composition of the atmosphere and oceans. The onset of the Indian monsoon and the desertification of sub-Saharan Africa can be related to the uplift of Tibet; the melting of midcrustal rocks and topographic collapse of mountain belts can be related to rapid denudation rates at the surface; and carbon sequestration in the oceans and atmospheres can be related to the formation and destruction of passive continental margins that are sites of carbonate deposition.
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From page 67... ...
Little is currently known about the dynamics of fluid conditions in the deeper parts of the crust. For example, the interior zones of well-developed strike-slip faults such as the San Andreas are thought to be much weaker than typical crustal rocks, and increased fluid pressures in the fault zone, perhaps dynamically maintained by the earthquake cycl itself, have been implicated as a possible cause of this weakness.
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From page 68... ...
Surprisingly, however, some of the most basic parameters of the lower crust, such as its average composition, are still poorly constrained, and the role of key processes, such as magmatic underplating, remains largely speculative. Better knowledge of the lower crust can be obtained from geochemical and rock~mechanical studies of tectonically exhumed sections, as well as from samples brought to the surface in volcanic eruptions and from geophysical research on active and ancient deformations.
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From page 69... ...
SAFOD will provide unique data on the composition and physical properties of fault zone materials at depth, the constitutive laws governing fault behavior, the stress conditions under which earthquakes initiate and propagate, and the role of fluids in active faulting. Two additional components, the Plate Boundary Observatory (PBO)
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From page 71... ...
A 4~ deep hole will be drilled through the San Andreas Fault zone close to the hypocenter of the 1966 Parkfield earthquake. Fault zone rock and fluid will be retrieved for laboratory analysis, and geophysical parameters, including seismicity, pore pressure, temperature, and strain, will be measured and monitored downhole and in adjacent areas.
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From page 72... ...
Recent space missions provide hints that Mars, which is much smaller than the Earth, has had plate tectonics and a planetary magnetic field in the distant geological past, although neither is currently observed. Why the Earth is so different from its planetary neighbors in terms of these global features remains the subject of considerable mystery and controversy.
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From page 73... ...
. The Core Dynamo and Magnetic Field The core dynamo generates the geomagnetic field through complex electromagnetic and hydrodynamic interactions among convective motions within the rotating, highly conductive liquid outer core.
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From page 74... ...
Although the desire to understand the dynamo at a fundamental level continues to motivate studies of the geomagnetic field, there is a growing recognition that changes in the Earth's main field have important implications for a wide range of practical issues, including biological evolution, the production of carbon isotopes in the upper atmosphere by cosmic rays (essential for carbon dating) , and the exchange of angular momentum between components of the Earth system.
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From page 75... ...
Increased computational speeds, coupled with high-speed networks and languages capable of managing parallel computations, allow calculations to be made at higher resolution and with fewer compromises than ever before. These information technologies will play a central role in the processing of very large seismic data sets and the numerical simulations of seismic wavefields in heterogeneous, anisotropic media needed for data interpretation.
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76 BASIC RESEARCH OPPORTUNITIES IN EARTH SCIENCE Isocontour Plof for SB4~1 ~0.6% (blue) and -~.0% (red3 View from Top and South
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Coupled with careful field work, these new instruments permit reliable estimates of field paleointensity. Short-term variations in both direction and intensity not only furnish a means for malting high-resolution stratigraphic correlations, but also place important constraints on the processes that generate the geomagnetic field.
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From page 78... ...
Dots Tom these obse~stodes have been used to explore s Side range of physical phenomena, Tom the Bow in the E~b's liquid core, to the electrical conductivity of He solid Woe, to resonant hy~ms~etic osciNshons in the plasma environment of the ionosphere. From these studies much has been reamed, not only Tout the geoms~edc held per se, but also Tout
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From page 79... ...
The results of these advances have shed new light on the deep interior, and the coming decade will continue this evolution. The new generation of thermal ionization mass spectrometers, offering enhanced precision and sensitivity for radiogenic isotope analyses, has been complemented with inductively coupled plasma mass spectrometry (ICPMS)
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From page 80... ...
80 BASIC RESEARCH OPPORTUNITIES INEARTH SCIENCE (B) Geomagnetic Field Models (A)
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FIGURE 2.16 (A) Results of numerical simulations of the geomagnetic field of Glatzmaier and Roberts.
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From page 82... ...
Effective use of these new data will require both a broad-based effort to promote interaction between the Earth science and planetary science communities, and a substantial enhancement of analytical capabilities. Promise of Planetary Exploration Robotic exploration of the solar system is increasing rapidly.
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High-resolution geophysical observations, such as those collected by the Mars Global Surveyor (MGS) mission, are critical for identifying and understanding the geologic processes that shape solid planets.
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A lengthy period of analysis of satellite data, combined with other geophysical observations, is important for understanding the chemical and physical structure and dynamics of planets. Science Opportunities Continuing exploration of the solar system, particularly Mars, will provide both new opportunities and challenges for the Earth science and planetary science communities in the coming decade (Box 2.3~.
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From page 85... ...
~ has invigorated study of the physical, ~chemical, and mineralogical composition of Martian rocks in a way : : analogous~to what fixture returned samples will require. The lesson from these studies is that understanding detailed aspects of another planet (e.g., Gornposition of the planet, petrogenesis and planetary ~evolution, climate history, possible~existence~of lifer will require intensive~and~diverse stud~ies~with investigators: derived ~from~the planetary science and Earth science communities,~and beyond.
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From page 86... ...
~ These observations raise important questions about why the Martian dynamo behaved is o : : : : ~ ~ : ~ : : : ~ : ~ :: i:: : I: ~ ::: I: differently from that: of the Earth.~In addition, the magnetizations have been interpreted as ~ ~ : : : : ~ : : : :: the ~en:uivalent~of terrestrial seafloor Stripes that are the hallmark of Late tectonics. Although this~inte~pretation is controversial, the data~are of first-order importance.~Further ~ : ~ ~ ~ : effort in understanding~how planetary dynamos and: plate tectonics~might work~on Mars in comparison with the Earth is critical for accurately interpreting and understanding these data.
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From page 87... ...
:~ -- -a; 0- — - -- $ `~ ~~ -A 4-~-2~ 2- 1~ .~.~..~ .\ ~ -. - 240° 210° OR ~ a, ~ I I -1500 0 1500 180° 150° West Longitude ~ .- -9oo 1 20° t1uUKt; Z.18 Clues to the ancient magnetic field of Mars from the Mars Global Surveyor spacecraft.
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From page 88... ...
The necessary instrumentation is diverse, and includes advanced ion microprobes, mass spectrometers, and electron microscopes, as well as accelerator- and synchrotron-based analytical probes. This challenge, if met, is an important opportunity for the Earth science community.
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