Structural and morphometric irregularities of eroded Pliocene scoria cones at the Bakony–Balaton Highland Volcanic Field, Hungary

Scoria cones of the Mio-Pliocene Bakony–Balaton Highland Volcanic Field (BBHVF) are built up by wide range of volcanic rocks, including intercalated lava flows/dykes, pyroclastic breccias and scoriaceous lapilli with various degrees of welding or agglutination. According to K–Ar and Ar–Ar dating, ages of the fourteen scoria cones within the field span between 5.2 and 2.5 Ma. From these fourteen, seven cones were selected which are suitable for morphometric analysis, i.e. visible in the field and have identifiable boundaries. The morphometric data were either derived by manual measurement on topographic maps and by Digital Elevation Model-based calculations. Using the same input contour line data from 1:10,000 maps, basic cone parameters such as cone height, basal and crater width have been measured in order to calculate parameters like Hco/Wco ratio and average slope angle. The results of these ‘three-parameter’-based manual calculations have been compared to the DEM-based results in order to highlight the controls of degradation, pitfalls in morphometric parameterization and the differences between these two calculation methods. Based on the results, three main controlling conditions have been identified that are together responsible for the preservation and erosion of the scoria cones located in the BBHVF: (1) age of the cone, (2) climate during the degradation and the (3) inner architecture of the edifice. In terms of morphometric dating, the traditional, ‘three-parameter’-based method tends to give inaccurate results on (1) scattered and/or truncated cones and (2) on the edifices characterised by highly effusive behaviour during the emplacement.

► DEM-based slope angle provides accurate result than‘three-parameter’-based method.
► The precision of the relative dating methods decreases with increasing cone age.
► The scattered, truncated scoria cones distort the results of morphometric dating.