Morphometric analysis of scoria cones: the potential for inferring process from shape
Published:January 01, 2017
Karen G. Bemis, Margot Ferencz, 2017. "Morphometric analysis of scoria cones: the potential for inferring process from shape", Monogenetic Volcanism, K. Németh, G. Carrasco-Núñez, J. J. Aranda-Gómez, I. E. M. Smith
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Geometric analysis was used to define seven morphometric parameters for the description of the shape of scoria cones, including volume, orientation and five shape parameters (flat-topped-ness, steep-sided-ness, relative crater depth, crater slope and elongation). The measurement and analysis of these shape factors for five distinct scoria cone populations facilitated an exploration of the overlapping effects of growth and erosion processes on shape. Flat-topped-ness seemed to be insensitive to either growth or erosion, suggesting a dependence on eruption energetics. Most of the variation in steep-sided-ness originated from eruptions ending during variable (early to mature) stages of development (growth) and from erosional processes, although steep-sided-ness was also sensitive to eruption energetics (through fragmentation and its impact on the angle of repose). Steep-sided-ness was therefore a poor indicator of geomorphic age. Distinct types of scoria cone shape (ideal, gully, horseshoe, tilted, crater row, parasitic and amorphous) captured a variety of deviations in shape from the purely conical, yet the conical shape parameters differed little in average value between the shape types. The conical shape parameters captured the growth and erosion processes (e.g. ballistic delivery, tephra redistribution via avalanching and erosional transport) common to all scoria cones rather than the particular processes that made the shape types unique (e.g. breaching, rafting and wind effects).
Supplementary material: Locations of examples of the shape types are available at https://doi.org/10.6084/m9.figshare.c.3661907
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The nature and origin of the small-scale volcanic systems, generally referred to as “monogenetic”, have enjoyed an elevated level of interest during the past decade. There has been recognition that their ostensibly simple volcano types are a window into the nature of explosive volcanism, landscape evolution and the processes of magma generation in the Earth’s upper mantle. In the past few years, major conferences have offered specialized technical sessions dealing with monogenetic volcanism and there have been thematic conferences, such as the IAVCEI International Maar Conference series, which have provided a focus for discussion of volcanological and geochemical aspects of small-scale basaltic volcanism. Many new aspects of monogenetic volcanism have emerged and have clearly demonstrated that this volcanism can be very complex on a fine scale. This book is a collection of papers arising from two recent Maar Conferences (the fifth in Queretaro Mexico and the sixth in Changchun, China) and serves as a snapshot of current research on monogenetic volcanism.