Chapter 7 Overview, key implications and future research

Abstract

Overview and key implications The vast extent of many ignimbrites shows that eruptions have occurred on almost unimaginable scales, well beyond any modern human experience. Evidence is emerging that plumes derived from large pyroclastic currents have impacted climate and biota on a global scale, whilst certain types of ignimbrites (e.g. extensive rheomorphic ignimbrites) indicate particularly awesome styles of eruption and emplacement that are regionally devastating and which we do not fully comprehend. Such unimaginable eruptions are bound to occur again. If we are to interpret such catastrophic events correctly, and possibly even anticipate the impact of future occurrences, it is essential that ignimbrite sheet architectures are studied further in order to understand the mechanisms, rates and durations of the fundamental processes. Of particular importance in risk mitigation will be the understanding of early stages of such devastating eruptions. The new approaches and descriptive schemes presented in this Memoir are intended to stimulate and facilitate such future work. Below, we summarize the fourteen main points and key implications of our analysis of pyroclastic density current deposition. Many of the ideas are also directly applicable to the interpretation of other types of sediment gravity flow deposits, such as those from turbidity currents, debris flows and lahars. (1) We have reviewed significant recent advances in the understanding of particle transport, segregation and deposition. Valuable insights derive from laboratory experiments and computer models, from analogous processes in nature and in industry, and from observations of volcanic eruptions and their deposits. (2) Clasts in pyroclastic density currents are supported