Those photos were taken by my sister Deb Schultz at Point Beach State Park on the west shores of Lake Michigan. Common icicles hanging off your eaves form from snow melting on a warm roof. If the air temperature is below freezing, the dripping water solidifies. These lakeshore icicles have a different genesis.
Waves breaking near the shore send a spray of micro-droplets into the air. This humid mist is fine enough to disperse in the wind and spread over large areas. Droplets that land on damp sand are absorbed. But on a piece of driftwood something amazing happens.
When the wood becomes sufficiently damp, micro-droplets will adhere and flow to a nearby low point on the branch. Again, if the air temperature is below freezing, icicles can start to grow in the same multi-layer fashion as those on your eaves. If you look closely at the two driftwood photos you’ll see that icicles form at discontinuities in the branch — twigs, sharp bends, and bark fragments. With the steady lakeshore winds, these are the places an icicle most strongly adheres and grows.
The other two photos show icicles forming under a rock overhang. I was initially surprised at their close spacing. It appears they form just about anywhere they can when shielded from the wind. Some have even grown down to the lower rock, like a stalactite meeting a stalagmite. I suspect that when two icicles grow together, presenting a larger surface area to catch even more micro-droplets, their weight eventually causes them to detach and fall. You can see one of the fallen in that last slide.
One final observation … there does seem to be some differences in morphology between “normal” icicles and lakeshore icicles. The icicles on your eaves are fed from the top, with some water droplets making it all the way down to the tip before freezing. This creates the classic icicle shape.
Lakeshore icicles, once started, instead grow simultaneously along their entire length. This creates some novel shapes: more-rounded tips, convex bulges, webs and fans, and a generally rippled surface texture. And they’re probably much safer to eat than the ones from your roof.
Next Week in Sky Lights ⇒ Afocal Astrophotography Experiment
I received this updated photo from my sister today (Feb 2). You can see how what once looked like typical icicles have grown over time into a congealed mass, in places looking like a frozen waterfall. Also note how they are “cut off” near water level where liquid water melts them. Nature photography is so often about timing.
Several years ago, at Dave’s house here, there was a HUGE icicle that continued to grow for days and days. Underneath said icicle was an outdoor chair, and when the icicle reached it, it began to head up, like a J curve. I tried to photograph it, but it broke before I could get out there with my camera It was awesome!
That’s fascinating! Never seen that myself. If it ever happens again, definitely snap a pic and send it. I have a difficult time explaining how an icicle could “bend” since frozen water is very brittle. Best guess is that the water droplets were running down so fast that they splattered off the chair in one direction and started building the upward part of the icicle. But that would take some very exacting conditions.