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ABSTRACT:The terms used to define the clastic deposits related to volcanic activity have important implications for the society in volcanic regions. Taking into account the importance of using a common terminology when considering natural hazards in the Spanish-speaking world, this study presents a classification of volcaniclastic deposits. This classification attempts to integrate the terminology related to the formational and depositional processes (eruptive and non-eruptive) taking place at volcanoes with the resulting volcaniclastic deposits and their constituent components. The classification emphasizes on how both physical and temporal variations in volcanic activity are responsible for observed differences in the related deposits. The purpose of this classification is to be a reference for the Spanishspeaking scientific community in order to avoid the numerous inconsistencies derived from the existing translations from multiple authors. Additionally, we present a flow diagram in both Spanish and English to illustrate that this classification system can be used to define and classify consolidated/lithified, and unconsolidated deposits. The appropriate classification of volcaniclastic deposits and their constituents can ultimately improve the definition and communication of potential volcanic hazards.

We analysed the tephra record of Mt. Ruapehu for the period 27,097±957 to~10,000 cal. years BP to determine the largest-scale explosive eruptions expected from the most active New Zealand andesitic volcano. From the lithostratigraphic analysis, a systematic change in the explosive behaviour is identified from older deposits suggesting dry magmatic eruptions and steady eruptive columns, characterised by frothy to expanded pumice fabrics, to younger deposits that are products of unsteady conditions and collapsing columns, characterised by microvesicular, fibrous, and colour-banded pumice fabrics. The end-members were separated by eruptions with steady columns linked to water-magma interaction and highly unstable conduit walls. Dry magmatic eruptions producing steady plinian columns were most common between 27,097±957 and shortly after 13,635+ 165 cal. years BP. Following this time, activity continued with eruptions that produced dominantly oscillating unsteady columns, which engendered pyroclastic density currents, until~10 ka when there was an abrupt transition at Mt. Ruapehu since which eruptions have been an order of magnitude lower in intensity and volume. These data demonstrate long-period transitions in eruption behaviour at an andesitic stratovolcano, which is critical to understand if realistic time-variable hazard forecasts are to be developed.