Figure 1: Crystallinity of natural samples.
From: Determining volcanic eruption styles on Earth and Mars from crystallinity measurements
(a) Calculated crystallinity of volcanic deposits from XRD analysis plotted versus sample location. Samples are broadly organized by volcanic eruption style. The range of groundmass crystallinity (Cgm) of lava flows are indicated by purple bars. Increasing crystallinity with clast size for the 1886 Mt. Tarawera plinian eruption is indicated by a black arrow. The blue box indicates phreatomagmatic whole-rock samples that are severely altered/weathered. (b) Comparison of hand-picked Cgm to bulk ‘random sample’ crystallinity (Cwr). Dashed grey lines delineate the approximate division between phreatomagmatic and ‘magmatic’ eruption styles. The severely altered/weathered whole-rock Fort Rock (Sample L) phreatomagmatic material containing fresh groundmass glass is indicated in blue. Sample locations and descriptions are keyed to Table 1 by their ID labels indicated in parentheses.
