What do you suppose these are?

[Cabin Fever]

My wife and I often walk the roads and trails of the campground that is near to us. It's a US Corp of Engineers campground next to a large dam. Yesterdays walk we heard the lake moaning and pinging. The sounds were awesome. We also saw the designs below in the thin lake ice near the shoreline. What do you suppose they are? There were dozens, maybe hundreds, of these designs.

 

[zoomzoom]

Is ice fishing allowed on the lake? That can be an easy start to these.

They can also be natural drain holes. Here's a decent description.
http://lakeice.squarespace.com/drain-holes/

 

[Sourdough]

They are "GAS" bubble holes.

 

[Cabin Fever]

Is ice fishing allowed on the lake? That can be an easy start to these.

They can also be natural drain holes. Here's a decent description.
http://lakeice.squarespace.com/drain-holes/

Yes, icefishing is allowed, but there is no way these are made by ice anglers. The spider-like designs were in water not more than a few feet deep. Based on the link you posted, it names the design, an "upflow hole." Following the lead of the link you posted, it appears what we found is called an "ice star."
http://lakeice.squarespace.com/ice-stars/

Other sources call this shape, "ice octopus" or "ice spider." The pattern is likely due to small springs of groundwater flowing upward into the water near the lake's shallow shoreline.

 

[Cabin Fever]

They are "GAS" bubble holes.

I think they are from groundwater (small springs) welling up in shallow water and melting the thin sheet of ice.

 

[Sourdough]

It is gas from decomposing vegetation. It is typically confined to roughly 50 to 75 feet from shore, as that is where shore leaves and brush get flushed into the lake.

That it is an open hole in the ice is a function of late - late winter spring. The same observation can be observed in 3 or 5 feet thick ice.

 

[Cabin Fever]

It is gas from decomposing vegetation. It is typically confined to roughly 50 to 75 feet from shore, as that is where shore leaves and brush get flushed into the lake.

That it is an open hole in the ice is a function of late - late winter spring. The same observation can be observed in 3 or 5 feet thick ice.

You cannot see it in the photo, but we could. The lake bottom, where we saw the lake stars, is a pure sand bottom. No dead vegetation or weeds there. The designs are caused by tiny springs of groundwater welling up from the lake bottom.

 

[angie_nrs]

It's funny that you mention this. We were riding around over the weekend and saw these on a small lake and also in a small mooring area. The ice was thin in both spots. The lake had already melted and then refroze, so the ice was thin. Good to know what caused it.

 

[Cabin Fever]

It's funny that you mention this. We were riding around over the weekend and saw these on a small lake and also in a small mooring area. The ice was thin in both spots. The lake had already melted and then refroze, so the ice was thin. Good to know what caused it.

That's the exact same conditions of the lakeshore where we saw ours. The shoreline ice had completely thawed well into the lake. Then, we had a cold snap and the shoreline iced up with almost paper thin ice.