The Physics and Chemistry of Iceland Versus Mid-Ocean Ridge Hydrothermal Systems: Contrasting Boundary Conditions

Abstract

This section contains three papers on the chemistry and physics of hydrothermal systems on Iceland and on mid-ocean ridges. These contributions detail the contrasting styles of the two systems in detail. But before examining the specifics of these hydrothermal circulation systems, it is appropriate to step back and examine the differences from a broad perspective. The physical and chemical processes of a subaereal and a deep subaqueous hot spring are similar, except that the boundary conditions are dramatically different. These changing boundary conditions produce very different surface expressions of hydrothermal convection, and it is important to identify cause and effect. Below two examples are given of differences caused by contrasting land versus deep sea hydrothermal activity that result from the same physical and chemical principles operating under atmospheric and greater than 200 atmospheres of pressure, respectively. First, the effects of boiling or the lack thereof in the two systems is quite different. Second, the pattern of fracturing which controls permeability is, itself, controlled by very different pore pressure and thus effective stress regimes on land versus in the deep sea.