Topography of a composite relict rock glacier, Ślęża Massif, SW Poland

A detailed geodetic survey and, additionally, a map of slope covers have been carried out for a composite relict rock glacier on the slopes of Mt ?l??a (718 m a.s.l.), Sudetic Foreland, SW Poland. The survey allows one to distinguish the mobilisation, transition and accumulation zones and to define geomorphic features diagnostic for relict rock glaciers such as lateral ridges standing above a central depression, steep margins of the landforms in the transition and accumulation zones, as well as absence of distinct head scarps above. Furthermore, it indicates that the present‐day hydrographic pattern on the surface of relict rock glaciers has been superimposed on the relief inherited from the active landforms. The topography indicates that tension prevailed rather than compression during the development of the rock glaciers. Some of the features, such as small lateral lobes, developed probably as a result of the compressive flow, however. The pattern of the slope cover shows that it developed during activity of the rock glaciers and been modified afterwards due to solifluction.     

质地对土壤热扩散率的影响

土壤热性质的研究是分析地表能量平衡的重要途径之一,土壤热扩散率是表征土壤热性质的重要参数。根据非稳态一维热传导方程的差分解计算了不同质地土壤的热扩散率。结果表明,风干土热扩散率小于1.4×10-3 cm2·s-1,并随着时间的推移逐渐减小;土壤质地越轻土墒条件越好热量传输速度越慢。     

Simultaneous determination of thermal conductivity, thermal diffusivity and specific heat in sI methane hydrate

Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between −20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.     

On the importance of rock thermal conductivity and heat flow density in basin and petroleum system modelling

Basin and petroleum systems are routinely modelled to provide qualitative and quantitative assessments of a hydrocarbon play. The importance of the rock thermal properties and heat flow density in thermal modelling the history of a basin are well-known, but little attention is paid to assumptions of the thermal conductivity, present-day heat flow density and thermal history of basins. Assumed values are often far from measured values when data are available to check parameters, and effective thermal conductivity models prescribed in many basin simulators require improvement. The reconstructed thermal history is often justified by a successful calibration to present-day temperature and vitrinite reflectance data. However, a successful calibration does not guarantee that the reconstruction history is correct. In this paper, we describe the pitfalls in setting the thermal conductivity and heat flow density in basin models and the typical uncertainties in these parameters, and we estimate the consequences by means of a one-dimensional model of the super-deep Tyumen SG-6 well area that benefits from large amounts of reliable input and calibration data. The results show that the entire approach to present-day heat flow evaluations needs to be reassessed. Unreliable heat flow density data along with a lack of measurements of rock thermal properties of cores can undermine the quality of basin and petroleum system modelling.     

ŒDIPUS: a new tool to study the dynamics of planetary interiors

We present a new numerical method to describe the internal dynamics of planetary mantles through the coupling of a dynamic model with the prediction of geoid and surface topography. Our tool is based on the simulation of thermal convection with variable viscosity in a spherical shell with a finite-volume formulation. The grid mesh is based on the 'cubed sphere' technique that divides the shell into six identical blocks. An investigation of various numerical advection schemes is proposed: we opted for a high-resolution, flux-limiter method. Benchmarks of thermal convection are then presented on steady-state tetrahedral and cubic solutions and time-dependent cases with a good agreement with the few recent programs developed to solve this problem.
A dimensionless framework is proposed for the calculation of geoid and topography introducing two dimensionless numbers: such a formulation provides a good basis for the systematic study of the geoid and surface dynamic topography associated to the convection calculations. The evaluation of geoid and surface dynamic topography from the gridded data is performed in the spectral domain. The flow solver is then tested extensively against a precise spectral program, producing response functions for geoid as well as bottom and surface topographies. For a grid mesh of a reasonable size (6 × 64 × 64 × 64) a very good agreement (to within ∼1 per cent) is found up to spherical harmonic degree 15.     

Smooth profiles from τ (p) and X(p) data

Summary. We reduce the problem of constructing a smooth, 1-D, monotoni-cally increasing velocity profile consistent with discrete, inexact τ ( p ) and X( p ) data to a quadratic programming problem with linear inequality constraints. For a finite-dimensional realization of the problem it is possible to find a smooth velocity profile consistent with the data whenever such a profile exists. We introduce an unusual functional measure of roughness equivalent to the second central moment or 'Variance' of the derivative of depth with respect to velocity for smooth profiles, and we prove that its minimal value is unique. In our experience, solutions minimizing this functional are very smooth in the sense of the two-norm of the second derivative and can be constructed inexpensively by solving one quadratic programming problem. Still smoother models (in more traditional measures) may be generated iteratively with additional quadratic programs. All the resulting models satisfy the τ ( p ) and X( p ) data and reproduce travel-time data remarkably well, although sometimes τ ( p ) data alone are insufficient to ensure arrivals at large X; then an X( p ) datum must be included.