A study of Basalt fingers using experiments and numerical simulations in double-diffusive systems

Abstract

This study examined the evolution of columnar-basalt structures using simple laboratory experiments and numerical simulation in double-diffusive finger system. Effect of various parameters like Prandtl and Rayleigh numbers has been considered in the study. Columnar-basalts are geological formations observed in some of the ponded basalt-lava found at many parts of the world. They are prismatic rock joints having polygonal cross-section with straight edges and parallel faces. The typical cross-sectional dimensions vary from few centimeters to meter size and typical height from 30-50 meters. Hence the aspect ratio of the columnar-basalt in most cases is greater than 100. The limitations for the evolution of columnar basalts provided in the literature have been discussed. An order of magnitude analysis has been presented for the thickness of the unstable layer at the interface. In this paper, we demonstrate that the double diffusive finger convection system can produce features similar to those observed in columnar basalt and can serve as an alternative, plausible explanation for the evolution of columnar basalt structure.