Non-Sorted Circles (IMAGE) Umea University Caption Circles of soil surrounded by vegetation formed above the tree line in the Swedish mountains when the ground moves due to the soil freezing and thawing. Credit Marina Becher Usage Restrictions This photo may only be used in the context of this news release. 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.