Figure 9: The trade off between porosity and temperature of seawater saturated basalt for two bulk resistivity values, 70 and 15, which are appropriate for the CSEM results from the east Pacific Rise (Evans \etal, 1994) and the Reykjanes Ridge respectively, at 1 km depth below the seafloor. The curves were calculated using the upper HS bound and the variation of seawater resistivity with temperature given in the text.