A review of statistical tools for morphometric analysis of juvenile pyroclasts

Morphometric analyses are based on multiparametric data sets that describe quantitatively the shapes of objects. The stochastic nature of fracture formation processes that break up magma during explosive eruptions yields mixtures of particles that have highly varied shapes. In volcanology, morphometric analysis is applied to these mixtures of particles with diverse shapes for two purposes: (1) to fingerprint tephra from individual eruptions and use the fingerprints to distinguish among tephra layers and determine their extents and (2) to reconstruct eruption processes, by linking particles formed by known fragmentation processes in experiments with particles from natural pyroclastic deposits. Here, we review the most commonly adopted statistical techniques for morphometric analysis of pyroclasts. We provide sets of objects with different shapes, along with their morphometric data, in order to demonstrate and illustrate the methods. They can be used not only for addressing the processes of fragmentation during explosive eruptions, but also for the characterization of other types of solid particles with complex morphologies.