Elizabeth Herndon Stands on a Palsa (IMAGE) University of Tennessee at Knoxville Caption Elizabeth Herndon stands on a palsa, a patch of ground that has permafrost less than a meter below the soil surface. Using special instrumentation, Herndon collects soil water and measures oxygen in the pore space-- the void space within soil that can be filled by water or air. In the foreground is a bog area where permafrost has completely thawed and caused the ground to collapse and pool with water. Credit University of Tennessee, Knoxville Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.