IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3W_3B-P6

Date/Time: July 23 Poster

Understanding geomorphic data of monogenetic scoria cones
Gabor Kereszturi, Karoly Nemeth
Volcanic Risk Solutions, Massey University, Palmerston North, New ZealandE-mail: kereszturi_g@yahoo.com

The definition of a scoria (or cinder) cone traditionally refers to any kind of volcanic landform that has conicalgeometry, is dominantly composed of fragmented rocks (coarse ash to lapilli) of low silica content of any type (e.g.
basalt) and that is small in edifice volume (e.g. 0.1 to 0.00001 cubic km). Geomorphic data of scoria cones are often
used for understanding eruptive and degradation processes quantitatively and as discrimination factors for relative
age dating. One of the most common interpretations of scoria cones’ geomorphic data is that these geomorphic
parameters gradually decrease with age as the erosion processes smooth the cone morphology away from theEarth surface. Recently, an increasing number of studies have found evidence for a significant eruptive-control
on the morphology of scoria cones. This study aims to give a summary of the possible interpretations of thegeomorphic data of scoria cones in the light of the findings of new studies. Morphometric data extracted fromany source (e.g. Digital Elevation Models) carry information about both syn-eruptive and post-eruptive processes.
Therefore, the traditional morphology-based discrimination of edifice degradation stages and relative age groupingsof volcanic cones should be avoided; a distinction should be made between the syn-eruptive contribution andthe post-eruptive contribution before any further interpretation is carried out. For discrimination purposes, known
absolute ages should be used, thus the likely effect of erosion on the primary, syn-eruptive morphology can bequantified. Here we suggest that prior to any detailed morphological study on a cone-dominated field, a preliminary
assessment of the cone (e.g. eruption history) needs to be performed and cones grouped following their genetic(syn-eruptive) origin. If the grouping of edifices is based on eruptive similarities, then the initial morphologies should
be similar to each other and their subsequent degradation will likely follow the same pattern over time. Here we
provide numerous examples to support the syn-eruptive controls on scoria cone morphology and their long-term
effect on degradation rates and patterns under different climatic settings. A theoretical degradation model, by thecombination of long-term (e.g. rain splash erosion) and short-term (e.g. debris flow) mass wasting processes, isestablished to help the interpretation of geomorphic data. Due to the coupling mechanism between the eruptive
diversity and the degradation path of individual volcanoes, it is proposed that volcano degradation is not only theconsequence of age and climate, but of many other processes, such as number of ’event’ degradations and theerosion-resistance of pyroclastic materials exposed to the environment.

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