Ice rings on Dead Creek
I found large, unusual and eye catching feature on Dead Creek in Addison Vermont in mid-March 2013. It looked like the ice was covered with huge bull's eyes: large concentic circles around a central upflow hole (ice star). They appear to be an up-flow feature similar to ice octupi (ice stars) but they are much bigger. The biggest was around 400 feet in diameter.
The main ciruclar part of this ring system is about 400 feet across. The dark shadow coming in to the picture from the lower right is a tree shadow. Dark, branched inflow channels can be seen coming in from the lower edge and the right side.
Note: Most of the pictures of ice rings have had the contrast pushed as camera sensors are less effective at showing contrast than the human eye is at seeing it.
Dead Creek is an impounded creek with large amounts of wetlands surrounded by wildlife refuges and farms.
The temperatures leading up to March 21 when I discovered the rings.
It looks like it was warm enough from the 9th to the 14th to remove winter ice. In the colder weather up to the 18th it looks like it refroze (probably on the 16th). On the 18 th it got warm again and stayed near freezing thrugh the 21st. It snowed a couple inches on the on the 19th.
The rings probably form one at a time starting from an ice star at the center. The rings appear to be a result of water flowing up through the most recently formed ring crack and radially outward for a couple of feet. By then there enough weight has built up to crack the ice at the edge of the newly saturated ring. The new crack allows the water to flow up and repeat the process. Based on the speed that water penetrates fluffy snow (roughly an inch per second) the individual rings might form as quickly as a minute or less.