Cooling of the Kärdla impact crater: II. Impact and geothermal modeling

Impact and geothermal modeling was performed to explain hydrothermal alteration in a 4 km marine complex crater at Kärdla, Estonia. The impact modeling was used to simulate the formation of the crater and the post-impact temperature distribution in crater environment. The geothermal modeling accounted for coupled heat transfer and multi-phase fluid flow in a variably saturated medium. The modeling results suggest that strong convective fluid flow was initiated. During the first stage, the cooling was rapid due to the effect of the latent heat of vaporization, which efficiently decreased the temperature to the boiling point. The modeling results are consistent with geological observations.