We present experimental structure-I clathrate hydrate (methane, carbon dioxide, and methane-carbon dioxide) equilibrium and ice-melting data for mesoporous silica glass. In both cases, high capillary pressures result in depressed solid decomposition temperatures (clathrate dissociation and ice melting), as a function of pore diameter. Clathrate dissociation data show a significant improvement over existing literature data, which is attributed to the improved experimental techniques and interpretative methods used. Through application of a melting (or clathrate dissociation) modified Gibbs-Thomson relationship to experimental data, we determine similar values of 32 ± 2, 32 ± 3, and 30 ± 3 mJ/m2 for ice-water, methane clathrate-water, and carbon dioxide clathrate-water interfacial tensions, respectively. The data are important for the accurate thermodynamic modeling of clathrate systems, particularly with respect to subsea sedimentary environments, and should prove useful in the simulation of potential methane hydrate exploitation and carbon dioxide sequestration schemes.