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971.
John Gunn 《地球表面变化过程与地形》1981,6(6):595-597
Recent work by Láng (1977) on solutional erosion rates in limestone drainage basins in relation to rainfall contains serious errors and has a questionable logical basis. Although much sounder, Smith and Atkinson's (1976) work on erosion rates in relation to runoff also requires modification as it greatly overestimates erosion rates in two areas of New Zealand. Greater resolution could probably be obtained by relating autogenic runoff to the rate of solution by autogenic waters and by computing separate relationships for areas where solution takes place under open and closed system equilibrium conditions. These factors should be taken into account in the experimental design of future studies. 相似文献
972.
Creep,stable sliding,and premonitory slip 总被引:3,自引:0,他引:3
John M. Logan 《Pure and Applied Geophysics》1978,116(4-5):773-789
Summary The current status of laboratory investigations into creep, stable sliding and premonitory slip is reviewed and some new material is presented. It is postulated that pre-cut rocks and those with simulated gouge layers undergo a transition with increasing confining pressure from (1) stable sliding to stick-slip, to (2) sliding along the pre-cut with deformation of the country rock, to (3) homogeneous flow of the specimen without slip along the pre-cut. Stick-slip behavior is not always present. Decreasing displacement rates are found to enhance stick-slip. Mixtures of gouge are found to be significant in controlling the behavior of sliding with 10–20 percent of anhydrite mixed with quartz or clays mixed with anhydrite shifting the sliding mode from stable stick-slip or stick-slip to stable sliding, respectively. Premonitory slip may be one of the most significant short term precursors of earthquakes. Although widely recognized in the laboratory, little systematic work has been completed. Variations in pore pressure, resistivity and seismic velocities have been investigated. Clearly much work needs to be done into these topics before a clear understanding is achieved. 相似文献
973.
974.
Concentrations of Ca, Cd, Cu, Fe, and Pb and binding capacities for Cd, Cu, and Pb were determined for water samples collected
from 12 lakes in southwestern Maine using atomic absorption and ion-selective electrodes, respectively. Surface waters in
this area are soft and characterized by low pH. Some lakes were highly colored with refractory organics, whereas others had
very low organic carbon concentrations. Both Cu and Pb concentrations were positively correlated with organic carbon content.
Copper and Pb binding capacities were significantly correlated with organic carbon content, whereas Cd binding capacity was
positively correlated with pH, but not with organic carbon. Surface water binding capacity for Pb was greater than that for
Cu or Cd. More than 99% of the Ca from all waters studied was removed onto cationic exchange resins. Less than 1% of the total
Cu existed as cationic species in highly humic waters, whereas as much as 65% existed as cationic species in less huic waters.
Conversely, more than 99% of the Cd present in humic waters existed as cationic species, whereas as little as 50% existed
as cationic species in less humic, more alkaline waters. These correlative studies indicate that binding by organic carbon
is important for both Cu and Pb in this area and must be considered in models of trace metal speciation. However, Cd binding
in the same waters is not correlated with organic carbon, which does not need to be considered in speciation models for Cd. 相似文献
975.
With increasing pressure for development on one of California's greatest natural resources, her coastline, comprehensive land-use
planning becomes a necessity. One aspect of land-use planning is effective geologic mapping for the delineation of geologic
hazards. Geologists from the California Division of Mines and Geology undertook an evaluation of the feasibility of local
government implementation of the geologic policies in the 1975 California Coastal Plan, a plan designed to facilitate and
direct comprehensive coastal land-use planning. Operating under restrictions similar to those that would be encountered by
local agencies attempting to implement the policies, the Division of Mines and Geology personnel applied the geologic guidelines
to two areas in Mendocino County on the northern coast of California. Using limited data and reconnaissance mapping techniques,
reports and maps were prepared which delineated the geologic hazards that should be considered in coastal land-use planning.
It was apparent from the two studies that the types and detail of data required for the implementation of the geologic policies
of the Coastal Plan could be developed by local agencies only by augmenting their staffs to include trained geologists or
by using the services of outside consultant geologists.
Paper based on data collected for California Division of Mines and Geology Open-File Reports. 相似文献
976.
John B. Anderson Richard Wheeler Charles P. Dunning Sue Shepley Marion Fowke 《Environmental Geology》1978,2(2):67-78
A historical record of the effects of human development upon Lake Macatawa is established using geologic criteria. Significant
cultural events are recognized using the pollen record, particularly ambrosia/vesiculate pollen ratios, and occurrences of
detrital and chemical contaminants within the more recent sedimentary column. Detrital contaminants include such things as
cinder and ash from coal burning power plants and animal hair from early tanning operations. Trace metal contaminants, frequently
associated with specific industrial events, are particularly useful in establishing a modern sedimentary chronology.
The impact of human activity upon Lake Macatawa is measured using fossil diatoms. The advantage of this method of environmental
impact assessment is that it provides a historical perspective in which changes within an environment are related to its natural
conditions. 相似文献
977.
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980.