Development of inflation ridges over Lava tubes

Lava tubes carry lava over long distances in some flows. The pressure of lava can sometimes inflate active tubes, forming meter-scale topographic surface ridges above them. Based on finite element models of lava tube inflation, we propose analytical scaling relations that link inflation ridges to the internal tube pressure and the mechanical characteristics of the flow during inflation. Roof thickness, which depends on the age of the tube's roof and its elastic modulus, is an important parameter in this relation. Inflation ridges found in various lava flows appeared within the first 400 h of roof formation and could not be formed with a completely cooled tube roof. Observations are consistent with Young's modulus at the time of inflation of just a few GPa. This new method and scaling relations open the possibility of using inflation ridges as probes to the structure and history of both active and inactive lava flows.