Some irregularity in scoria cone degradation in lava spatter-dominated cones

NEMETH K; MARTIN U; HALLER MJ; RISSO C; MASSAFERRO GI

Zaragoza

Conferencia; 6th International Conference on Geomorphology; 2005

International Association of Geomorphologists

Pyroclastic cones in Argentina and Libya provide clues to the degradation of scoria cones in dry climate. Progressive changes due to erosion are considered to be represented by the decrease with increasing age of morphometric parameters, such as scoria cone height, cone height/width ratio, crater depth/width ratio, and slope angle. Comparative morphology of scoria cones is considered to be a useful dating tool for volcanic fields. However here we demonstrate, that initial cone morphology depends on the eruptive style generated the ejecta construct. The potential role of phreatomagmatism, mafic sub-Plinian intermittent stages of the cone development and potential lava spatter fed eruptions may significantly alter the initial cone-like architecture of the volcano which determines the further erosional shape modification of the cone. In lava spatter-dominated cones the erosion is rather controlled by the development of arcuate cracks on various part of the cone that were related to withdrawal of magma at the end of and/or during the eruption. Collapse features are common in the outer flank of such volcanoes, especially in those areas, where post-volcanic lacustrine activity may undercut the lower volcanic flank, leading to form steep outer slopes features. These slopes maybe preserved for a long time in dry climate and may resemble young morphology.