Figure 3: Effects of alteration.
From: Determining volcanic eruption styles on Earth and Mars from crystallinity measurements
Comparison between relatively fresh and weathered/altered samples from the same localities for phreatomagmatic samples. (a) Phreatomagmatic Columbia River basalt hyaloclastite fresh-picked glass (black line) and palagonitized bulk analysis (grey line). (b) Whole-rock analyses of weathered (grey line) and fresh (black line) tuffaceous material from Fort Rock (USA). An increase in peak intensity relative to that of the amorphous hump between 10–40° 2θ in weathered/altered samples corresponds to increased crystallinity in both samples.
