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Global Volume Distribution for Subaerial Volcanism on Earth

Figure 4
Global distribution of eruption volumes for VEI 0 – 8 eruptions. a) Distributions obtained by maintaining separation between eruptions belonging to different VEI classes. The red and orange symbols on one side, and the blue and green symbols on the other side, refer to data with only consistent, or including inconsistent (respectively) volume attribution in the LaMEVE database. The orange symbols belong to the red distribution, with different color used to evidence the volume range over which eruptions with VEI 4 and 5 overlap with eruptions with VEI 0 – 3. The green symbols have the same meaning, with reference to the blue distribution. The slopes of the two overlapping branches are significantly lower than for the eruptions with larger volumes. b) Same as for panel a), after reconstruction of the global distributions (see paper). For both the red and blue data sets, after an initial close-to-log-normal portion the distribution displays a unique slope which satisfactorily approximates a (tapered) power law distribution (p-values reported in the figure). Red data points in panel b (including the orange ones in panel (a)) refer to 336 eruption cases (151 for VEI 0 – 3 from the LV database, the rest from the LaMEVE database: 80 for VEI 4; 36 for VEI 5; 24 for VEI 6; 31 for VEI 7; 14 for VEI 8). Blue data points in panel b (including the green ones in panel (a)) refer to 373 eruption cases (151 for VEI 0 – 3, 89 for VEI 4; 40 for VEI 5; 26 for VEI 6; 40 for VEI 7; 27 for VEI 8).

Papale P., W. Marzocchi, D. Garg (2021).
Journal of Geophysical Research – Solid Earth,

Plain Language Summary

The occurrence of volcanic eruptions over the Earth follows apparently complex patterns: while the vast majority of the eruptions are relatively small in size, here and there less frequent large eruptions appear, and even less frequently, cataclysmic eruptions take place menacing vast regions up to the global Earth. Summed up with relatively quick deterioration of the information from the geologic record, especially for small to medium size eruptions, such apparently irregular trends have largely limited our understanding and forecasting capabilities. New databases of volcanic eruptions, and new statistical analyses, allow us to determine the size distribution of volcanic eruptions worldwide, from the smallest lava flows to the largest explosive eruptions known to have occurred on Earth. We find that above a relatively small eruption volume threshold all eruptions distribute according to what is called a power law, which is also known to describe other natural phenomena such as earthquakes, wild fires, and many others. The mechanisms subtending the generation of a power law distribution for the global continental volcanism are not immediately clear. However, as for several other similarly distributed phenomena, a relevant implication may be the impossibility to predict the size of an impending eruption, with severe consequences for volcanic risk emergency management.