The influence of regional stress and structural control on the shape of maar craters

Abstract

Maars are volcanic craters surrounded by ejecta rings. The craters are excavated by subsurface explosions, commonly attributed to the interaction of magma and groundwater in phreatomagmatic explosions. Maar craters have a variety of shapes and sizes, but commonly are elongate. This paper explores the relationship between the orientation of maar elongation and regional stress indicators. The orientations of maar elongation, regional faults, and nearest neighbor lineaments containing maars were measured in seven volcanic fields: Auckland (New Zealand), Lamongan (Indonesia), Newer Volcanics Province (Australia), Pali Aike (Argentina), Pinacate (Mexico), Macolod Corridor (Philippines), and Serdán Orientale (Mexico). Common maar orientations were observed in several fields and compared with faulting and nearest neighbor lineaments. It was found that the distribution of maars was commonly correlated with regional stress indicators including regional faults and lineaments of aligned vents, but the orientation of elongation of those maars did not always correlate with stress indicators. Maars not aligned with stress indicators were likely influenced by more local effects, including changes to the subsurface stress regime from the ongoing eruption.