ALBERT

Description / Table of Contents: Geochemistry is a science that is based on an understanding of chemical processes in the earth. One of the principal tools available to the chemist for understanding systems at equilibrium is thermodynamics. The awareness and application of thermodynamic techniques has increased at a very fast pace in geosciences; in fact, one may be so bold as to say that thermodynamics in geology has reached the "mature" stage, although much future thermodynamic research is certainly needed. However, the natural processes in the earth are often sluggish enough that a particular system may not reach equilibrium. This observation is being supported constantly by new experimental and field data available to the geochemist e.g. the non-applicability of the phase rule in some assemblages, the compositional inhomogeneities of mineral grains, the partial reaction rims surrounding original minerals, the lack of isotopic equilibration or the absence of minerals (e.g. dolomite), which should be present according to thermodynamics. The need to apply kinetics has produced a large number of papers dealing with kinetics in geochemistry. As an initial response to this growing field, a conference on geochemical transport and kinetics was conducted at Airlie House, VA, in 1973, sponsored by the Carnegie Institution of Washington. The papers there dealt with several kinetic topics including diffusion, exsolution, metasomatism and metamorphic layering. Since 1973 the number of kinetic papers has continued to increase greatly. Therefore, the time is ripe for a Short Course in Kinetics, which brings together the fundamentals needed to explain field observations using kinetic data. It is hoped that this book may serve, not only as a reference for researchers dealing with the rates of geochemical processes, but also as a text in courses on geochemical kinetics. One of us has found this need of a text in teaching a graduate course on geochemical kinetics at Harvard and at Penn State during the past several years. Finally, it is our hope that the book may itself further even more research into the rates of geochemical processes and into the quantification of geochemical observations. The book is organized with a rough temperature gradient in mind, i.e. low temperature kinetics at the beginning and igneous kinetics at the end (no prejudices are intended with this scheme!). However, the topics in each chapter are general enough that they can be applied often to any geochemical domain: sedimentary, metamorphic or igneous. The theory of kinetics operates at two complementary levels: the phenomenological and the atomistic. The former relies on macroscopic variables (e.g. temperature or concentrations) to describe the rates of reactions or the rates of transport; the latter relates the rates to the basic forces operating between the particular atomic or molecular species of any system. This book deals with both descriptions of the kinetics of geochemical processes. Chapter one sets the framework for the phenomenological theory of reaction rates. If any geochemical reaction is to be described quantitatively, the rate law must be experimentally obtained in a kinetically sound manner and the reaction mechanism must be understood. This applies to heterogeneous fluid-rock reactions such as those occurring during metamorphism, hydrothermal alteration or weathering as well as to homogeneous reactions. Chapter 2 extends the theory to the global kinetics of geochemical cycles. This enables the kinetic concepts of stability and feedback to be applied to the cycling of elements in the many reservoirs of the earth. Chapter 3 applies the phenomenological treatment of chapter 1 to diagenesis and weathering. The rate of dissolution of minerals as well as the chemical evolution of pore waters are discussed. The atomistic basis of rates of reaction, transition state theory, is introduced in Chapter 4. Transition state theory can be applied to relate the rate constants of geochemical reactions to the atomic processes taking place. This includes not only homogeneous reactions but also reactions that occur at the surface of minerals. Chapter 5 discusses the theory of irreversible thermodynamics and its application to petrology. The use of the second law of thermodynamics along with the expressions for the rate of entropy production in a system have been used successfully since 1935 to describe kinetic phenomena. The chapter applies the concepts to the growth of minerals during metamorphism as well as to the formation of differentiated layers (banding) in petrology. Chapter 6 describes the phenomenological theory of diffusion both in aqueous solutions and in minerals. In particular, the multicomponent nature of diffusion and its consequence in natural systems is elaborated. Chapter 7 provides the atomistic basis for the rates of reactions in minerals. Understanding of the rates of diffusion, conduction, order-disorder reactions or exsolution in minerals depends on proper description of the defects in the various mineral structures. Chapter 8 provides the kinetic theory of crystal nucleation and growth. While many of the concepts in the chapter can be applied to aqueous systems, the emphasis is on igneous processes occurring during crystallization of a melt. To fully understand both the mineral composition as well as the texture of igneous rocks, the processes whereby new crystals form and grow must be quantified by using kinetic theory. Due to space and time limitations (kinetics!) some topics have not been covered in detail. In particular, the mathematical solution of diffusion or conduction equations is discussed very well by Crank in his book, Mathematics of Diffusion, and so is not covered to a great extent here. The treatment of fluid flow (e.g. convection) is also not covered in the text.

Description / Table of Contents: A new experimental method for measuring the soil-water diffusivity of frozen soil under isothermal conditions is introduced. The theoretical justification of the method is presented and the feasibility of the method is demonstrated by experiments conducted using marine-deposited clay. The measured values of the soil-water diffusivity are found comparable to reported experimental data.

Description / Table of Contents: Summary: A microscopic method for the determination of particle-size distributions of pulverized snow was worked out. The method gives satisfactory distribution curves, presenting the number of particles as a function of their cross-sectional "areas". The measurements were made by means of a filar micrometer eyepiece, the snow particles being placed on a ruled glass slide, which was submerged in silicone oil to prevent evaporation. The time for the determination of a distribution can be appreciably shortened by estimating the size of the particles instead of measuring them, though the accuracy is not so high in this case.

Description / Table of Contents: Summary: Apparatus was built for deforming ice crystals under hydrostatic pressures up to 350 atmospheres. Single crystals were placed in the mounts in such a way that the deformation occurred by gliding on the basal glide plane. It was found that the shear strain rate increased as the pressure was increased at constant temperature, but that the rate is practically independent of hydrostatic pressure when the difference between the ice temperature and the melting point is kept constant.

Description / Table of Contents: Summary: A series of deformation measurements have been selected for preliminary studies on the plasticity of Greenland glacier ice. The measurements to be reported on were obtained in the Red Rock and TUTO tunnels in Northwest Greenland. Both tunnels were excavated during the summer of 1955 with some additional work done during the summer of 1956. Deformation measurements made up to the end of the 1956 summer season, therefore, are of limited reliability, but certain trends appearing in these data seem worth reporting. The topics discussed are (1) the shearing of an initially vertical peg system at Red Rock, (2) the deformation of core holes at TUTO, and (3) tunnel closure at both sites. These data are analyzed on the basis of laminar flow of the Nye type and certain conclusions are derived.

Description / Table of Contents: Summary: The compressive strength of snow cylinders was investigated as a function of age of snow, snow-particle size, and age of the cylinders. The effect of gases such as carbon dioxide, methane, and ammonia on the strength of snow cylinders has also been studied. The experimental results show that the older the snow from which snow cylinders are made, the smaller the compressive strength. The compressive strength of cylinders decreases with the snow particle size. An equation describing the aging curves for snow cylinders is presented. Whereas carbon dioxide and methane in small quantities have no effect on the compressive strength, ammonia appreciably lowers the compressive strength of snow cylinders. All strength measurements were carried out at -10°C.

Description / Table of Contents: Summary: Measurements were made with 22 more or less hydrophobic polymers and lacquers at intervals of 5 or 10 min for periods up to 1 hr. All surfaces were carefully cleaned, and some surfaces were baked. Highest initial (time 0) average contact angles ( 106° - 106.6°) were measured for Foster Snell rain repellant wax, Barrett 25-218 water repellant varnish (air-dried), and Cardolite NRL-7241. After 40 min, contact angles for these substances were 95.6°, 90.9°, and 91.0°. The measurement apparatus is illustrated, and data are tabulated.

Description / Table of Contents: Summary: Laboratory experiments on the air permeability of various screened and natural snows are described, and, results are analyzed to determine whether the parameters obtained from the measurements could be used to define a snow type. The permeability of a snow sample of known porosity (calculated from density) was determined over a wide range of air velocities; the sample was then compacted artificially a few mm, its density was determined, and its permeability measured again. The procedure was used to obtain curves for several densities of the same sample. Air flow appeared laminar for velocities less than 5 cm/sec in fine-grained snow (less than 0.8 mm in diam.), 2 cm/sec in medium-grained snow (0.8-1.2 mm diam.), and 1 cm/sec in larger-grained snow. A formula is presented expressing all of the results obtained under laminar-flow conditions in a single relationship, and an equation for estimating grain size from initial permeability and initial porosity is suggested. Snow conversion tables and a discussion of the effect of varying sample porosity on its permeability are appended.

Description / Table of Contents: Summary: An analysis of snow-cover density, temperature, and hardness data, measured over a period of several years at five stations in Alaska and six stations in the Canadian Arctic, shows the snow cover in the Canadian Archipelago to be colder, denser, and harder than in the interior of Alaska. A series of nomographs were developed to estimate average monthly snow-cover density from mean monthly air temperature and wind velocity. The nomographs are applicable for the months November through March, for the Alaskan and Canadian area north of 62°N latitude, and for elevations below 1500 ft. A comparison of observed snow-cover densities with those derived from the nomographs indicates that the method will provide a reliable regional estimate of snow-cover density. Studies of the relation between snow-cover temperature and air temperature from November through March disclosed the snow to be on the average from 4°C to 9°C warmer than the air at the Alaskan stations and 4.5°C warmer at the Canadian Archipelago stations. An investigation of snow-cover hardness revealed regional variations similar to that for density. Measured snow hardness during the period of no melting was found to be related to densities between 0.15 and 0.36 g/cm^3.

Description / Table of Contents: Réalisation d'un modèle climatique simple tenant compte des principaux processus d'échanges énergétiques (le transfert radiatif est traité en ondes courtes et en ondes longues) dans l'atmosphère et permettant de restituer à l'équilibre les propriétés du profil de température. Un schéma de génération de la nébulosité (la génération de l'épaisseur optique est faite en distinguant 3 étages de nuages) est couplé à la procédure d'ajustement convectif, pour tenir compte de la réponse de la couverture nuageuse. Tests de sensibilité à la constante solaire et à la couverture nuageuse. Attention particulière accordée à la sensibilité de la température et du bilan radiatif de surface à une augmentation de la concentration en CO2. Il serait intéressant de poursuivre le travail en incluant un schéma de dissipation indépendante des flux de chaleur latente et sensible, de façon à se libérer de la contrainte d'un gradient de température convectif.

Description / Table of Contents: This volume contains papers presented at the Geological Society on March 25th and 26th 1981, plus three additional contributions by researchers who were unable to be present at the meeting. The meeting brought together earth scientists with interests in geomorphology, geochemistry, pedology, sedimentology and applied geology. The multidisciplinary approach to the study of residual deposits is reflected in the 25 chapters of this book, which are arranged in four main groups: Weathering processes (chapters 1-3); Kaolinites, laterites and bauxites (chapters 4-11); Red beds (chapters 12-14); Duricrusts: calcretes, silcretes and gypcretes (chapters 15-25). The last two chapters of the book deal with karst related fluorite-baryte deposits, and Cenozoic pedogenesis and landform develop- ment in south-east England. Richard Crockett, Andrew Goudie and Don Highley provided invaluable suggestions during the planning of the meeting that led to this book. R. C. L. WILSON,Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA.

Description / Table of Contents: Although the search for oil and gas in Europe, particularly in the North Sea, has been very successful, it has become progressively more difficult and costly in recent years. The need for continuing exploration success in finding accumulations of hydrocarbons has created a climate which favours the use of modern scientific and technological methods and techniques. Amongst these is petroleum geochemistry. Applications of petroleum geochemistry (integrated with petroleum geology) in petroleum exploration has drastically changed in recent years from a post-mortem science to a widely accepted exploration predictive tool.

Description / Table of Contents: Ice forces on a bridge pier in the Ottauquechee River, in Quechee, Vermont, were measured by installing fourpanels-each capable of measuring forces in the normal and tangential direction - on both sides of a vertical V-shaped pier nose. The measured forces are presented for a short period during an ice run. After the ice run, the thickness and sizes of the ice floes were measured and the compressive strength of the ice was determined in the laboratory from the ice samples collected along the river banks. The water level measurements made at several locations along theriver are also presented for the period of the ice run.

Description / Table of Contents: Recent observations of shore ice pile-up and ride-up along the coast of the Alaska Beaufort Sea are presented. Information is given to show that sea ice movement on shore has overridden steep coastal bluffs and has thrust inland over 150 m, gouging into and pushing up mounds of beach sand, gravel, boulders and peat and, inland, the tundra material. The resulting ice scar morphology was found to remain for tens of years. Onshore ice movements up to 20 m are relatively common, but those over 100 m are very infrequent. Spring is a dangerous time, when sea ice melts away from the shore, allowing ice to move freely. Under this condition, driving stresses of less than 100 kPa can push thick sea ice onto the land.

Description / Table of Contents: The probability density function of the gouge depths into the sediment is represented by a simple negative exponential over four decades of gouge frequency. The exceedance probability function is, therefore, e to the -lambda d, where d is the gouge depth in meters and lambda is a constant. The value of lambda shows a general decrease with increasing water depth, from 9/m in shallow water to less than 3/m in water 30 to 35 m deep. The deepest gouge observed was 3.6 m, from a sample of 20,354 gouges that have depths greater than or equal to 0.2 m. The dominant gouge orientations are usually unimodal and reasonably clustered, with the most frequent alignments roughly parallel to the general trend to the coastline. The value of N(bar) sub 1, the mean number of gouges (deeper than 0.2 m) per kilometer measured normal to the trend of the gouges, varies from 0.2 for protected lagoons to 80 in water between 20 and 38 m deep in unprotected offshore regions. The distribution of the spacings between gouges as measured along a sampling track is a negative exponential. The form of the frequency distribution of N sub 1 varies with water depth and is exponential for lagoons and shallow offshore areas, previously skewed for 10 to 20 m depths off the barrier islands, and near-normal for deeper water. As a Poisson distribution gives a reasonable fit to the N sub 1 distributions for all water depths, it is suggested that gouging can be taken as approximating a Poisson process in both space and time. The distributions of the largest values per kilometer of gouge depths, gouge widths, and the heights of the lateral embankment of sediments plowed from the gouges are also investigated.

Description / Table of Contents: An evaluation of an impulse radar system for detecting cavities under concrete pavement is discussed, and field results are presented. It was found that a dual antenna mode of surveying was ideal for void detection. In this mode one antenna operated in a transceive mode and a second, offset from the first, operated in a receive-only mode. This arrangement allowed a refraction-type profile survey to be performed, which enabled subpavement voids to be easily detected. Field trails were held at Plattsburgh Air Force Base, where 28 cavities were detected and mapped. Drilling of holes verified that a cavity existed and allowed cavity depth to be measured. The cavities varied from 1.5 in. to 23 in, depth and were up to 20 ft. long.

Description / Table of Contents: This paper documents the development and verification of two finite difference models that solve the general two-dimensional form of the heat conduction equation, using the alternative-direction implicit method. Both can handle convective, constant flux, specified temperature and semi-infinite boundaries. The conducting medium may be composed of many materials. The first program, ADI, solves for the case where no change of state occurs. ADIPC solves for case where a freeze/thaw change of phase may occur, using the apparent heat capacity method. Both models are verified by comparison to analytical results.

Description / Table of Contents: A review on past experimental and theoretical work indicates a need for additional experimentation to characterize the response of snow to inelastic pressure waves. Pressure data from previously conducted explosion tests are analyzed to estimate the elastic limit of snow of 400 -kg/cu m density to be about 36 kPa. This pressure corresponds to a scaled distance of 1.6 m/cu.rt.kg for charges fired beneath the surface of the snow, and to a scaled distance of 1.2 m/cu.rt.kg for charges fired in the air. The effects of a snow cover on the method of clearing a minefield by using an explosive charge fired in the air above the snow surface are also discussed and recommendations are given for further work in this area. Explosive pressure data are used to estimate the maximum effective scaled radius for detonating buried mines at shallow depth to be 0.8 m/cu.rt.kg. Fuel-air explosive will increase this effective radius significantly because of the increase in the size of the source region.

Description / Table of Contents: The presence of snow on the ground can impose limitations on the mobility of wheeled and tracked vehicles. Snow depth and density are the two most easily measured snow properties that can be related to mobility over snow. Existing models of snowpack accumulation and ablation processes and models of internal snowpack structure were examined to determine if a model of the snowpack can be developed for use in predicting the snow parameters that affect mobility. Simple models, such as temperature index models, do not provide sufficient snowpack details, and the more detailed models require too many measured inputs. Components of the various models were selected from a basis of a snowpack model for predicting snow properties related to mobility over snow. Methods of obtaining the input data from some components are suggested, and areas where more development is needed are described.

Description / Table of Contents: A sea ice model was applied to the East Greenland Sea to examine a 60-day ice advance period beginning 1 October 1979. This investigation compares model results using driving geostrophic wind fields derived from three sources. Winds calculated from sea-level pressures obtained from the National Weather Service's operational analysis system resulted in strong velocities concentrated in a narrow band adjacent to the Greenland coast, with moderate velocities elsewhere. The model showed excessive ice transport and thickness build-ups in the coastal region. The extreme pressure gradient parallel to the coast resulted partially from a pressure reduction procedure that was applied to the terrain-following sigma coordinate system to obtain sea-level pressures. Additional sea-level pressure fields were obtained from an independent optimal interpolation analysis that merged FGGE buoys drifting in the Arctic basin with high latitude land stations and from manual digitization of the NWS hand-analyzed Northern Hemisphere Surface Charts. Modeling results using winds from both of these fields agreed favorably.

Description / Table of Contents: An analysis of ice fracture that incorporates dislocation mechanics and linear elastic fracture mechanics is discussed. The derived relationships predict a brittle to ductile transition in polycrystalline ice under tension with a Hall-Petch type dependence of brittle fracture strength on grain size. A uniaxial tensile testing technique, including specimen preparation and loading system design was developed and employed to verify the model. The tensile strength of ice in purely brittle fracture was found to vary with the square root of the reciprocal of grain size, supporting the relationship that the theory suggests. The inherent strength of the ice lattice and the Hall-Petch slope are evaluated and findings discussed in relation to previous results. Monitoring of acoustic emissions was incorporated in the tests, providing insights into the process of microfracture during ice deformation.

Description / Table of Contents: Ice accreted on high-speed rotors operating in supercooled fog can be thrown off by centrifugal force, creating severe unbalance and dangerous projectiles. A simple force balance analysis indicates that the strength of accreted ice and its adhesive strength can be obtained by measuring the thickness of the accretion, the location of the separation, the rotor speed, and the density. Such an analysis was applied to field and laboratory observations of self-shedding events. The results agree reasonably well with other observations.

Description / Table of Contents: Summary: Laboratory experiments on the creep of sifted snow under uniaxial, hydrostatic, and confined-side compressive stresses are described, and the results are discussed on the basis of an additive theory for combined stresses. Stress (4-40 psi) and temperature (-3.6°C to -13.6°C) dependence was investigated for 35 samples (initial density = 0.4 g/cm^3) subjected to uniaxial and hydrostatic stress for 200-sec time increments. Another series of 104 samples (initial densities 0.36-0.63) was subjected to uniaxial, hydrostatic, and confined-side compressive stresses until an arbitrary change in density was reached. In all cases the applied stress ultimately became a shear stress acting between grains, the open structure reacting differently to combined stresses and separate uniaxial stresses. An activation energy of 13,400 cal/mol was obtained from the first group of tests.