Constraints on the effusive volcanic eruptions that formed Kallistos Vallis, Venus

Kallistos Vallis is a Venusian channel system that extends >1200 km downslope from a source region marked by a graben-like feature and chaotic terrain, terminating at distal plains mantled by extensive volcanic flows. Some channel reaches are as wide as tens of kilometers and are in places characterized by the presence of prominent streamlined erosional residuals about which the system anastomoses. The areas of topographic disturbance at the head of Kallistos Vallis are interpreted as the surface expressions of a deeply-rooted igneous plumbing system that conveyed large volumes of mafic or ultramafic magma to the surface from subcrustal depths. Lava flows with depths of 5 m and 20 m and viscosities of 1 Pa s would have been fully turbulent on essentially all channel slopes, and could have reached velocities of up to tens of meters per second and discharges of up to similar to 10(7) m(3)/s on slopes no greater than 1 degrees. Flows with these properties are expected to have had a capacity for thermomechanical incision of at least several meters per day, facilitated by the relatively high gravitational acceleration and temperatures of the Venusian surface. The system could have developed in as little as tens of days but development by multiple discrete eruptive episodes separated by much longer periods of inactivity is also possible. The minimum total volume of effused lava required for development of component channels of Kallistos Vallis is as great as similar to 7000 km(3). The eruptive and flow conditions predicted for Kallistos Vallis underscore the remarkable differences between the predominant character of volcanism on modern Earth and that which prevailed on large rocky bodies during earlier episodes of solar system history.

Automated summary

Kallistos Vallis is a channel system on Venus that extends over 1200 km from a source region marked by a graben-like feature and chaotic terrain, terminating at plains covered in volcanic flows. The channels are wide, reaching tens of kilometers, with prominent streamlined erosional residuals. The topographic disturbances at the head of Kallistos Vallis are likely caused by a deep-rooted igneous plumbing system, which transported large volumes of mafic or ultramafic magma to the surface. The development of the system could have occurred in tens of days, but multiple eruptive episodes separated by longer periods of inactivity are also possible. The minimum total volume of lava required for the development of Kallistos Vallis is estimated to be around 7000 km(3), suggesting significant differences between the volcanism on Venus and modern Earth.