Change of stress field in Beta‐Atla‐Themis Region on Venus, estimated from surface geometry of dike swarms, lava stratigraphy and crater density

Abstract

We estimate the orientations of crustal stress on Venus from surface geometry of dike swarms associated with volcanoes. The inferred stress field sometimes has various orientations even in the same region. Using lava stratigraphy, volcanoes in the Beta‐Atla‐Themis (BAT) region are classified into three groups: volcanoes before, during and after the formation of corona chains. Dike swarms in each group show a similar stress orientation. Between the first two groups, the compressional stress orientation had changed from a N‐S trend to a trend parallel to the strike of the corona chains. The stress fields during and after the corona chain formation are similar. The crater densities of the two volcano groups are 1.67±0.94 × 10−6 and 0.86±0.36 × 10−6 km−2, respectively, which indicates a probable age difference (>108yr). The stress field and volcanic activity before the corona chain formation in the BAT are probably associated with adjacent rift activity in Beta Regio. Those during the corona chain formation may be attributed to a mantle upwelling centered at Atla Regio.