Source to sink: A review of three decades of progress in the understanding of volcaniclastic processes, deposits, and hazards

Abstract

Volcaniclastic sediments, broadly defined as clastic deposits derived from the transport, deposition and/or redeposition of the products of volcanic activity, have long been a Cinderella of the geosciences. This status is a function of the inherent complexity of the fragmentation, transport and depositional processes that operate in volcanically-impacted environments and the comparatively recent development of the discipline as a specialist area. Volcaniclastic studies are truly interdisciplinary, drawing on many elements of physical volcanology, fluid dynamics, classical clastic sedimentology, hydrology and geomorphology. In the past 30 years volcaniclastic studies have blossomed, partly in response to a number of catastrophic and high-profile volcanic eruptions, including Mount St. Helens in 1981, Nevado del Ruiz in 1985 and Pinatubo in 1991, and partly due to integration with the maturing science of fluid dynamics and an increased understanding of the behaviour of particulate dispersions and two-phase granular flows. These historical events have demonstrated that the sedimentary repercussions of volcanic eruptions can have more severe, far-reaching, and prolonged impacts than the initial volcanism. In parallel, studies of well-preserved examples from the geological record have extended our understanding of landscape and environmental responses to styles and scales of volcanism that have not been recorded historically, such as the impacts of caldera-forming eruptions from silicic calderas. As a consequence, studies have expanded beyond classical stratigraphic and sedimentological studies of ancient successions in a variety of plate tectonic settings to a more dynamic focus on process. Ultimately, volcaniclastic successions are the product of the interplay between the volcano, in terms of the style, magnitude and explosivity of the eruption, and the environment, as expressed by physiography, hydrology, energy, and accommodation space.