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A global heat flow map has been derived from existing observations supplemented in areas without data by an empirical predictor based on tectonic setting and age. In continental areas the predictor is based on the observed correlation of heat flow with age of last tectono-thermal event, and in oceanic regions on the observed relation of heat flow to age of ocean floor. The predictor was used to assign mean heat flow values to 5° × 5° grid areas on the globe, weighted according to the relative area of tectonic provinces represented. A spherical harmonic analysis to degree 12 of the heat flow field yields a mean value of 59 mW m−2, a rms residual of 13 mW m−2, and an amplitude spectrum which decreases gradually and almost monotonically fromn = 1. The spherical harmonic representation of the heat flow field is free of the unreal distortions which have characterized earlier analyses based on a geographically sparse data set. Areas with residuals greater than 15 mW m−2 comprise less than 19% of the area of the globe, thus indicating that most heat flow provinces have characteristic dimensions adequately represented in a 12-degree analysis.

The gravitational potentials of a point mass, a spherical cap, and a spherical rectangle are presented in a spherical harmonic framework. The point mass displays the richest harmonic spectrum at all degrees. Equal mass distributed as a spherical cap or rectangle shows loss of representation at high degrees; the spectral weakening moves to progressively lower degrees as the mass is distributed more widely. The spectrum of a cap is less smooth than that of a similar rectangle with the same area. The characteristics of these three mass configurations are compared with those of other mass distributions and modeling techniques.

The velocity of crack propagation in glass plates has been measured. The plates were strained until fractures were initiated. Measurements made over various small segments of the crack path show variations in crack velocity from 0.01 to about 4 km/sec. The velocity of propagation appears to be related to the strain-energy distribution. Regions of the plate where the strain energy was high prior to fracture yielded the highest crack velocities.

The motion near a seismic source is synthesized from experimentally obtained seismograms of non-dispersed body waves. The body waves were emitted from an explosive source submerged in a lake with a frozen surface. The seismograms were recorded at several distances by moving the source to a greater depth for each record, while the seismometer remained in a fixed position on the surface ice sheet. All syntheses of the waveform one meter from the source yield the impulsive nature of the source. Deviations between the synthesized one-meter record and the observed one-meter motion are thought to reflect primarily the changing character of the shot medium with depth from the ice. These results indicate that over the short propagation distances (about three wavelengths for the higher frequencies recorded) through the simple medium of this experiment, the observed waveforms and their associated spectra retain characteristics of the source function. The records also yield some information regarding the nature and structure of the elastic medium about the source.

The near equality of the terrestrial heat flux in both oceanic and continental regions suggests that higher temperatures may exist under oceans than under continents at a specified depth. Dissimilar temperature profiles in these regions give rise to thermal displacements and stresses that may contribute to several tectonic features. With the temperature profile at the juncture of the ocean and continent as a reference, the continent is a center of relative contraction and the ocean a center of relative expansion. The computed thermoelastic displacement field reveals a general upward movement at mid-ocean, horizontal displacement at the juncture toward the continent, and downward movement at mid-continent. The field of maximum shear stress indicates normal shearing at the surface of the expanding ocean and reverse shearing at the surface of the contracting continent, with a null near the margin where the sense of the shear changes. Null zones are also found beneath both the continent and the ocean at depths of about 100 km, but these zones do not connect at the margin. Rather, the zone of normal shear appearing at the surface of the ocean bends downward near the margin to merge with a region of normal shear existing beneath the null on the continental side. This zone of normal shear dipping beneath the continental margin compares in some characteristics with the loci of earthquake hypocenters in the circum-Pacific seismicity belt.

The general solutions are derived for steady heat conduction in an n-layered half-space and sphere with arbitrary constant heat production and thermal conductivity in each layer and specified flux and temperature at the surface. The solutions are presented in a form convenient for rapid numerical calculations. The given solutions can be readily transformed to allow thermal conductivity to be any function of the local temperature.

EIGHT new heat flow measurements from Precambrian sites in the Republic of Zambia (Fig. 1) range between 55 and 76 mW m−2. Compared with the mean for Precambrian provinces elsewhere, these results are anomalously high by some 50%. This heat flow anomaly persists after taking into account radioactive heat generation of near surface rocks, and therefore may be interpreted as indicating the presence of anomalously warm material only a few tens of kilometres beneath the Earth's crust. We believe these observations support the hypothesis of an incipient arm of the East African rift system as proposed by Fairhead and Girdler1,2 and suggest that it may extend into the central African plateau to at least 16°S.

Dissimilar temperature profiles beneath oceans and continents give rise to thermoelastic stresses at and adjacent to the oceanic-continental margin. Computations of the magnitude and orientation of the maximum shear stress field reveal a zone of shear dipping beneath the continent from the margin.

Formulas are presented to compute, without reference to tables, the north-south and east-west components of the tidal accelerations due to the moon and sun at any point on the earth's surface at any given time. These results supplement the formulas of Longman, which give the vertical and horizontal components due to each body but which do not give the azimuthal decomposition of the horizontal components.

A deterministic digital model to simulate evaporite sedimentation permits experimentation with depth of water, shape of salt basin, number, position, and strength of the inlets, and rate of evaporation. It provides a reasonable fit to salt thickness and distribution in the Upper Silurian Salina Formation of Michigan.

VERY low heat flow values of 18±2 mW m−2 (0.42±0.04 µcalorie cm−2 s−1) and 22±2 mW m−2 (0.51±0.05 µcalorie cm−2s−1) have been determined for two sites 85 km apart on the West African Precambrian shield in the Niger Republic (Table 1).

The gravitational attraction of the continents produces a force field at the surface of the earth, similar in geometry to lithospheric displacements deduced from studies of earthquake focal mechanisms.