摘要:

Local differences in rate of heat transfer in vapor and by conduction through the ground in hot spring areas are difficult and time‐consuming to measure quantitatively. Individual heavy snowfalls provide a rapid low‐cost means of measuring total heat flow from such ground. After a favorable snowfall (heavy, brief duration, little wind, air temperature near 0°C), contacts between snow‐covered and snow‐free ground are mapped on a suitable base. Each mapped contact, as time elapses after a specific snowfall, is a heat‐flow contour representing a decreasing rate of flow. Calibration of each mapped contact or snow line is made possible by the fact that snow remains on insulated surfaces (such as the boardwalks of Yellowstone's thermal areas) long after it has melted on adjacent warm ground. Heat‐flow contours mapped to date range from 450 to 5500 μcal/cm2sec, or 300 to 3700 times the world average of conductive heat flow. The very high rates of heat flow (2000 to>10,000 μcal/cm2sec) are probably too high, and the lower heat flows determinable by the method (<500 μcal/cm2sec) may be too low. Values indicated by the method are, however, probably within a factor of 2 of the total conductive and convective heat flow. Thermal anomalies from infrared imagery are similar in shape to heat‐flow contours of a test area near Old Faithful geyser. Snowfall calorimetry provides a rapid means for evaluating the imagery and computer‐derived products of the infrared data in

ISSN:0148-0227    

DOI:10.1029/JB074i022p05191

年代:1969

数据来源: WILEY

摘要:

A new set of weighted means of observed periods of free oscillations are used to estimate an earth model by least‐squares inversion. All observed modes are considered, but only the fundamentals plus1S0and2S0are used explicitly in the inversion. The method uses partial derivatives of period with respect toPvelocity,Svelocity, and density. Derivatives of period with respect to the size of the core affect the periods of low‐order spheroidal modes by as much as 0.8 sec/km of change. The model is developed in two stages. First, geophysical arguments that are generally independent of inferences from free oscillations are used to develop an approximate earth model, HT11GS1. Secondly, inversion is used to derive from it a new model, DI‐11, which fits the observed periods with an overall rms deviation of only 0.61 second. DI‐11 is characterized by a rapid increase in density at depths 500 to 800km, an Adams‐Williamson density below 1100km, a density jump of 2 g/cm3at the base of the outer core, and a shear velocity of 2.18 km/sec in the inner core. The existence of a solid inner core gets some support from the observations of free osc

ISSN:0148-0227    

DOI:10.1029/JB074i022p05202

年代:1969

数据来源: WILEY

摘要:

The geology of the margins of the Mono basin, California, suggests that the basin is a relatively shallow warp. When interpreted in the light of detailed study of the basin fill and of the geologic history of the region, the gravity and seismic data are consistent with the basin's being filled to a depth of 1 to 1.5 km, largely with sedimentary deposits. The geophysical data have been interpreted by others to indicate that the basin subsided deeply along nearly vertical faults and is filled to a depth of approximately 5 km with Cenozoic deposits, including a large volume of volcanic material. The basin appears to be the product of a regional pattern of warping and faulting and is not to be regarded as a volcano‐tectonic depression, as has been suggeste

ISSN:0148-0227    

DOI:10.1029/JB074i022p05221

年代:1969

数据来源: WILEY

摘要:

The deformation of the earth's crust under superposed loads is considered as a problem in structural mechanics. The crust is treated as a uniform, elastic, thin, spherical shell, and the mantle is treated as an enclosed viscous liquid. Equations relating loading and crustal response are developed. Loadings may be spatially concentrated, locally distributed, or global and may be applied as a steady‐state or transient condition. Crustal displacements under reservoir loadings, glacial sheets, and sea‐level rises are predicted and agree well with observations both in magnitude and in time. The Wisconsin glaciation in North America is treated in particu

ISSN:0148-0227    

DOI:10.1029/JB074i022p05240

年代:1969

数据来源: WILEY

摘要:

The distribution of slopes over any finite span on a surface excavated by primary impact craters is derived from a representation of the surface as a ‘moving average’ of impact events. The cumulants are always positive, and they are large for typical mare crater densities. In some cases the distribution can be approximated by a rapidly convergent Gram‐Charlier type A series. The slope distribution has a much higher peak near zero slope and also has much heavier tails than a Gaussian distribution with the same variance. Under some conditions the slopes have approximately a symmetric stable distribution law with characteristic exponent one unit smaller than the crater diameter population index. Observations of slopes in Mare Cognitum are in good agreement with theory, if the validity of the photoclinometric data and the model can be acc

ISSN:0148-0227    

DOI:10.1029/JB074i022p05253

年代:1969

数据来源: WILEY

摘要:

The micrometeoroid experiments on the OGO 2 and OGO 4 satellites are described. The aim of the OGO 2 experiment was to measure the velocities, masses, and orbits of dust particles in the earth's dust cloud. No orbits were determined, and it is questionable whether any micrometeoroids of mass>10−12g impacted on the sensors during the 1300 hours in which good data were obtained. The OGO 4 experiment was modified in an attempt to measure a flux obviously much smaller than previously anticipated. No micrometeoroids capable of penetrating 4000 A of Al have impacted on ionization sensors of total effective area 5 cm2ster during 3000 hour exposure. Thus, we find that the flux of micrometeoroids>10−12g in the neighborhood of the earth is less than 2×10−3particles/m2sec 2

ISSN:0148-0227    

DOI:10.1029/JB074i022p05268

年代:1969

数据来源: WILEY

摘要:

Measurements of strong‐field magnetization over the temperature range −196° to 700°C have been made on forty‐eight drill core samples of tholeiitic basalt from Alae and Makaopuhi lava lakes, Kilauea volcano, Hawaii. These samples were originally obtained at temperatures ranging from 50° to 1020°C. Nearly all samples contain abundant hemoilmenite with Curie temperatures in the range −100° to −160°C. Samples quenched from high temperatures (800° to 1000°C) have second Curie temperatures ranging from 150° to 290°C, due to unoxidized titanomagnetite, and samples obtained at lower temperatures (50° to between 400° and 700°C) have second Curie temperatures ranging from 500° to 580°C. This transition from medium to high Curie temperatures occurs between 850° and 300°C, varying from one drill hole to another, and is accompanied by a marked increase in the strong‐field magnetization at room temperature. Oxidation of original titanomagnetite to Ti‐poor titanomagnetite containing ilmenite lamellas is the cause of the increase in Curie temperature. Comparison of the compositions of the oxide minerals with the oxygen fugacity data of Sato and Wright and the equilibrium reaction data of Buddington and Lindsley shows that oxygen fugacity was controlled largely by the buffering action of the oxide minerals; hence titanomagnetite was oxidized, whereas the more abundant hemoilmenite was little changed as the lava cooled. This oxidation occurred at temperatures well below equilibrium, the difference being generally of the order of 100°C but as much as 400°C. We conclude that in some basaltic lavas the magnetic minerals may form through subsolidus reactions at temperatures well below their final Curie temperatures. In such lavas the natural remanent magnetization is a mixture of thermoremanent magnetization and high‐temperatu

ISSN:0148-0227    

DOI:10.1029/JB074i022p05277

年代:1969

数据来源: WILEY

摘要:

It is possible to easily measure variations of intensity of the earth's gravity field by orbiting two geometrically identical satellites spaced about 200 kilometers apart and equipped to measure their relative velocity. The velocity difference is related to the space gradient of the potential field, which is a totally different concept of measurement, compared with present methods that measure the long‐term integrated effects of gravity on orbit elements. It is expected that one month of satellite time would yield one set of measurements of the gravity anomalies of the entire earth with sensitivity at least 1 mgal ten times better than present world surveys. The cost is comparatively small and, in view of cost reduction for other related programs, may even be a substantial saving in tota

ISSN:0148-0227    

DOI:10.1029/JB074i022p05295

年代:1969

数据来源: WILEY

摘要:

The relationship betweenK, the level of potash content in lavas erupted from an andesite volcano, andh, the depth to the center of the inclined seismic (Benioff) zone beneath the volcano, is extended using new data from Indonesia, the Lesser Antilles, and New Zealand. Coefficients of correlation betweenKandhof +0.86 (K55) and +0.80 (K60) are obtained by straight‐line regression. This is compared with a coefficient between K55and distancedof the volcano from the trench of only +0.60. The coefficients of correlation ofKagainsthmin, which is the depth to theuppersurface of the Benioff zone, are not significantly different from those betweenKand

ISSN:0148-0227    

DOI:10.1029/JB074i022p05301

年代:1969

数据来源: WILEY

摘要:

A discussion is presented on the physical significance of the Voigt, Reuss, and Hill averaging methods of calculating the isotropic properties of anisotropic crystals and the bulk properties of poly crystalline aggregates of solids. It is shown: (1) that Reuss' average rather than Hill's average is to be identified with the elastic constant that is observed under high‐pressure static compression of rocks, (2) that Reuss' average is also suitable for the isotropic representation of an anisotropic crystal, and (3) that the difference between the Reuss and Hill values is a measure of the nonelastic properties of rock

ISSN:0148-0227    

DOI:10.1029/JB074i022p05311

年代:1969

数据来源: WILEY