 The research team witnessed and documented rock movement on December 20, 2013, that involved more than 60 rocks, with some rocks moving up to 224 m between December 2013 and January 2014 in multiple movement events.These observations contradicted earlier hypotheses of winds or thick ice floating rocks off the surface.Instead, rocks move when large ice sheets a few millimeters thick floating in an ephemeral winter pond start to break up during sunny days.