摘要:

(STM and AFM) are allowing for in situ (in air and under water) imaging of mineral surfaces at previously unattainable nanometer to atomic scales. The four images, which represent a range of STM/AFM applications, were all taken on [001] surfaces of hematite. Counterclockwise from bottom left, these micrographs are described as follows: (1) An STM image of oxygen sites on terraces separated by steps—imaged under oil at ‐300‐mV sample bias. The difference in tunneling current between terrace (blue) and step‐edge (pink) sites can be related to differences in local electronic structure that may affect the reactivity of the different sites Terraces step downward toward the lower left. A kink site is apparent along one step. (2) An AFM image in air showing the molecular‐scale structure of the hematit

ISSN:0002-8606    

DOI:10.1029/EO072i010p00105-01

年代:1991

数据来源: WILEY

摘要:

Coastal erosion, flooding of low‐lying coastal areas, disruption of ecosystems, probable population relocation, and economic loss are some consequences of projected relative sea‐level rise. The term includes both the rise anticipated to result from global warming and other factors, and the rise from local tectonic subsidence. Some specific sites were discussed at the annual meeting of the American Association for the Advancement of Science, held in Washington, D.C., February 14–19.In comparing the New York City and eastern Mediterranean coasts, Victor Goldsmith of Hunter College, New York, presented a case for stabilization versus retreat of coastal areas, dependent on the geologic terrane and on the degree of development. The 578‐mile New York City coastline is considered “hard,” meaning some sort of cement structure, such as roads, jetties, or piers, separates the water from the coast. It is also an area of many beaches that are not natural, but that have been built up and maintained by the process of sand nourishment over the past 50 years. The Rockaway peninsula, for example, has received more than 12 million cubic yards of sand between 1926 and 1962 in response to the measured sea‐level rise of 30 cm in the last 100 years from downwarping of the wide continental shelf, said Goldsmith. Because land is highly developed and expensive in this area, retreat is not a practical option. Goldsmith suggests that the effects of on‐going sea‐level rise, at rates of about 1 foot per century, can be offset by continued hardening of the New York City coastline and beach nourishmen

ISSN:0002-8606    

DOI:10.1029/EO072i010p00106-01

年代:1991

数据来源: WILEY

摘要:

On October 9, 1990, a lively group of more than 60 scientists from around the world gathered at Northeastern University's Henderson House in Weston, Mass., to spend 4 days in concentrated efforts to unravel the complexities of cusp/cleft theory and observations.Plans for the National Science Foundation‐sponsored workshop were formulated at the previous GEM workshop convened by Ted Rosenberg at the University of Maryland in October 1989, where participants agreed that the first task of the first GEM campaign—attacking problems of the magnetopause, boundary layers, and their signatures in the ionosphere—should be the identification of cusp signatures in ground‐based and airborne data by intercalibrating with spacecraft data on direct over

ISSN:0002-8606    

DOI:10.1029/EO072i010p00109

年代:1991

数据来源: WILEY

摘要:

As science advances, important changes rapidly ripple through many disciplines and lead to radically new interpretations of old data, so argued Thomas Kuhn (The Structure of Scientific Revolutions, University of Chicago, 1970). Such a scientific revolution is now taking place, as scientists revise models of the mineral‐solution interface. These revisions extend through such disparate fields as materials science (for example, the synthesis of thin oxide films) and medicine (for example, biomineralization), as well as through the Earth sciences.The Mineralogic Society of America sponsored the short course “Mineral‐Solution Interface Geochemistry,” to summarize some of these advances. The course, organized by Michael Hochella of Stanford University and Art F. White of the U.S. Geological Survey, was held at the Tanglewood Resort near Dallas, Tex., October 25–28, 1990. Hochella and White also edited a book to accompany the short course, which is published as volume 23 of the Reviews in Mineralogy and available at low cost th

ISSN:0002-8606    

DOI:10.1029/90EO00085

年代:1991

数据来源: WILEY

摘要:

Hugh Ducklow of Horn Point Environmental Laboratories, University of Maryland‐CEES, Cambridge, Md., has been appointed an editor of theJournal of Geophysical Research‐Oceansto serve a 4‐year term ending December 31, 1994. His primary responsibility will be for papers relating to biological oceanography with special emphasis on the production dynamics of the upper ocean. Ducklow will also encourage more process‐oriented biologists to publish inJGR‐Oceans.Ducklow intends to raise the profile ofJGRamong biological oceanographers and increase the number of biology articles published in the journal. Ducklow reports that in 1990 only about 20 of more than 300 articles inJGR‐Oceanswere biological. He would like to see the Oceans section continue to expand its role as a stage for presenting collections of articles about major field programs, including the first JGOFS process studies. Also, the launch of the Sea‐WIFS ocean color sensor in 1993 promises to open a new era in biological oceanography and Ducklow plans to ensureJGRbecomes one of the principal outlets for ocean

ISSN:0002-8606    

DOI:10.1029/EO072i010p00111-02

年代:1991

数据来源: WILEY

摘要:

In the spirit of glasnost, the first stage of a state‐of‐the‐art seismological network for global research on Earth structure, earthquakes, and seismic monitoring of nuclear testing is now operating in the Soviet Union, thanks to cooperation between several U.S. and Soviet groups and agencies. Digitally recorded seismic data have been generally unavailable from the Soviet Union prior to the new agreement, leaving an essentially uninstrumented hole in the largest continent on Earth. In 1988 the Soviet Academy agreed to a joint research program with the Incorporated Research Institutions for Seismology (IRIS) and the U.S. Geological Survey that called for the establishment of 20–25 permanent seismic stations and the operation of portable seismic networks in each country. The U.S. State Department approved the incorporation of the seismic program, now called the Eurasian Seismic Studies Program, under Area IX (Earthquake Prediction) of the Bilateral U.S./U.S.S.R. Environmental Protection Agreement. The network is operated by IRIS, a consortium of over 60 American universities, the USGS, and the Institute of Physics of the Earth (IPE) of the Soviet Academy of Sciences. Principal project scientists are Jonathan Berger, a geophysicist at Scripps Institution of Oceanography, and John Filson, a seismologist

ISSN:0002-8606    

DOI:10.1029/90EO00090

年代:1991

数据来源: WILEY

摘要:

A new study of magnetic profiles and other plate tectonic data in the Indian Ocean predicts that India and Australia, previously thought to move in unison as part of the same rigid plate, are approaching each other at about 12 mm/year. According to conventional plate tectonic theory, plates are internally rigid with earthquakes concentrated at plate boundaries and occurring only rarely in plate interiors. However, many large earthquakes occur within the conventionally defined plate interior between Australia and India [Stein and Okal, 1978;Bergman and Solomon, 1985]. The Indian Ocean earthquakes are scattered over many hundreds of kilometers, a region much larger than the ∼1–20 km width of typical ocean plate boundaries. Questions exist concerning how much motion is taken up by the deformation represented by the earthquakes, and whether this shows that tectonic plates def

ISSN:0002-8606    

DOI:10.1029/EO072i010p00113-01

年代:1991

数据来源: WILEY

摘要:

Popular concerns over global resource issues have focused attention on the description of the dynamics of hydrologic processes at scales much larger than the traditional river basin. Improved, remotely sensed land surface data on a global scale and improved large‐scale global circulation models (GCMs) have fueled the need to better integrate hydrologic processes with land surface features and atmospheric dynamics. Until recently, however, the interaction between climate modelers and hydrologists has been weak.Given a prescribed geographic distribution of sea surface temperature, GCM models can approximately simulate long‐term, large area mean precipitation, runoff, and other hydrologic variables. Runoff is the amount of precipitation leaving an area in surface drainage in contrast to that which infiltrates into the subsurface. Some hydrologists have been involved in so‐called “effects” modeling, in which they attempt to use GCM output to assess the sensitivity of hydrologic systems to global warming. These efforts have made hydrologists painfully aware of the incompatibility of temporal and spatial scales between the GCMs and basin‐scale hydrologic models in common use. GCM model simulations with and without mountains have been used to demonstrate the role of the mountains in controlling soil wetness in the North American mid‐continent “Manabe, 1990”. Improvements in spatial resolution of the land surface does affect model performance, particularly in the influence of orographic processes and the scale‐dependence of the representation of mountain‐induced gravity wave drag. Simulation of runoff at the river basin scale using a GCM “pot model” (a lumped representation of hydrologic processes) has been compared with simple nonlinear soil moisture models. The results suggest that runoff predicted by the GCM has statistical characteristics much more similar to the rainfall input of the model itself than it does to actual observed runoff. Incorporation of a relatively simple representation of the soil moisture dependence of infiltration, along with a simple representation of base flow, leads to much better agreement with the statistical character of simulated runoff. Hydrologic characterization of large areas will improve as spatially distributed soil moisture modeling continues to evolve and remotely sensed data becomes available from the Earth Obse

ISSN:0002-8606    

DOI:10.1029/90EO00095

年代:1991

数据来源: WILEY

摘要:

Recent studies of the motion of the Pacific and North American plates show that plate tectonic motion averaged over several years equals that averaged over several million years, suggesting that the motion of tectonic plates is steady. Until recently, the only method of measuring the speed of one plate relative to another was through analysis of the magnetic anomalies above mid‐ocean ridges. As two plates move apart over millions of years, the direction of the geomagnetic field is frozen into the new crust formed by cooling magma that fills the gap opened between the diverging plates. The geomagnetic field occasionally reverses polarity, and these reversals are frozen into the crust, causing highs and lows in the magnetic field sensed above the young seafloor at mid‐ocean ridges. Rates of motion are deduced from the spacing between dated magnetic highs and l

ISSN:0002-8606    

DOI:10.1029/EO072i010p00115-01

年代:1991

数据来源: WILEY