Compaction of Hyaloclastite from the Active Geothermal System at Krafla Volcano, Iceland

Figure 6

Porosity and permeability evolution with increasing effective pressure for the different hyaloclastites. Here, the initial porosity measurement (in black) is made by He-pycnometry for all samples. For the two shallower samples, subsequent porosity measurements are extrapolated by monitoring the volume change in the pumps as the effective pressure is increased via continuous and noncontinuous approaches (blue line and blue symbols, respectively). Permeability is also measured at increasing pressure increments, highlighting the different susceptibilities of the materials to permeability reduction via compaction. For the surface material, we observe a change in the slope of porosity and permeability as a function of effective pressure, marking . The dashed lines connecting the discrete porosity and permeability measurements are for visual clarity and offer no statistical significance.