Abstract: | The problem of a pressure or volume increase due to the vertical redistribution of two substances with differing compressibilities is considered and compared with a previous treatment. Modified expressions for the pressure and volume changes are obtained using the general equation of state with constant compressibility. The effects of gas and melt compressibilities, and also of the solubility of gas in floating bubbles, on pressure and volume changes in magmatic systems are discussed. Very different conclusions from those in the previous treatment are found. |