The maximum stone that we measured during the moves of the winter of 2013-14 was about 22kg. Several of the natural stones with obvious new trails probably were more than 30-40 kg. The biggest stones (~300kg) on the playa did not move during the winter of 2013-4. This mechanism may, depending on water depth, duration of freezing temperatures and wind velocity be capable of moving the largest stones on Racetrack playa. We are looking forward to a precipitation event large enough to flood the playa to more than 150mm depth. It could however be a long wait.

The 320 kg stone is far out on the playa and currently rests near a mid playa shoreline. It appears that during most pond-forming events, the playa does not completely flood, or does not remain flooded for very long. Hence, it must be an unusual precipitation event that could mobilize the 320 rock. I suspect that the stone was moved by a process similar to what we describe in the paper, but it could be that the ice was thicker than was the case for the rock movements we observed. The pond that last moved the 320 kg rock must have been deeper than the pond we observed, since the rock was positioned a bit beyond the highest strand-line of the pond we studied. A deeper pond could, presumably, form a mobile floating ice sheet that is thicker than the one we studied. It is also possible that the rock is moved by very thin ice that forms a 'ice pile-up". Such pile-ups are common on mid-latitude and polar lakes during ice breakup and can damage lake-shore trees and homes, so thick ice may not be necessary for rock movement.