Natural Ice Sculptures

March 1, 2013 Comments Off on Natural Ice Sculptures

This past Saturday, I started the Master Naturalist Training at Sugarloaf. The main theme for the day was geology, so naturally we headed for the beach to explore the rocks. What a beautiful surprise was awaiting us there. The heavy northeasterly winds of late had blown reams of Lake Superior ice into the Cove.  Beautiful pancake ice was floating in the open water, and sky blue chunks of ice peeked and alternated out from beneath piles and piles of white layers. Two ice volcanoes were erupting on the beach, with fair size waves blasting up the volcano and then sending chunks of ice, which moments before had been floating on the surface, up through the volcano to build a new ice shoreline.

February and March are the usual peak months for maximum ice on the lake. We got a slow start this year, but there is enough ice finally to cover the western nose of the lake, so the past week or two traveling around Duluth has shown ice regularly there, with some minor shifting around. But I hadn’t seen anything that resembled floating ice up the shore at all this winter. It used to be that Lake Superior froze over at least briefly every 10 years or so. Granted if it does freeze over, it is rarely for more than twenty-four hours because of all the currents and the fact that ice chunks on Lake Superior rarely are any thicker than about 4 inches, which makes it easier for the currents, waves and winds to break up the ice and shift it around. It also usually requires many days in a row of well sub zero temperatures, something we have not seen for a few years. One of the course participants commented that a complete freeze of Lake Superior may never happen again, a rather somber but likely true thought.

Types of Ice

A number of types of ice form on Lake Superior and other large bodies of water. The most common and usually first to form is called an ice foot. This forms along the shoreline largely from splashes of water freezing over surfaces. It can freeze, break up and move, then form new ice with chunks of the previous formation now jumbled together. One of my favorite versions of this type of formation are ice “bowls” that form over cobbles then get turned by waves. Thin sheets of ice can form, then be broken up by waves making layers of thin angular shapes that slide over each other and make wonderful noises as they slide past each other to pile and unpile.

Ice Bowls at Sugarloaf Cove

Pancake ice can form in a couple ways. Slushy ice can freeze together into roundish sorts of shapes, get tumbled and moved around with other similar chunks. The clunking together pushes up the edges and gives pancake ice is telltale rim around the edge. The center of this version of pancake ice stays lumpy in the center. Sheet ice can also become pancake ice over time with the same process just described, but instead of being lumpy on the inside it remains smooth because its original ice form was smooth.

Pancake Ice in center of picture

Pressure ridges build along the shoreline when wind pushes ice against an immovable barrier. A strong wind can give us piles and piles of ice against a shoreline, built up into jagged peaks often 8-10 feet or more thick. This is layer upon layer of ice refrozen together and many of the different layers are easily visible. This is what we have at Sugarloaf right now. (See top picture) Often a closer look at these individual layers of ice will reveal lots of bubbles frozen in a line through the ice from top to bottom. The ice can also look like hundreds of individual icicles froze together with the usual assorted lumps and bumps along the edges. These ridges of ice often stay once they have landed, and I predict that the layers now resting in Sugarloaf will likely stay through the season unless we get another set of strong northeasterly winds to break them up. Because of where Sugarloaf is situated these are the only winds that can make much of a change in the ice of the cove.

Looking at ice formations is a fascinating way to pass lots of time! The sea caves on the south shore of Lake Superior often provide a wonderful show, provided that the ice piles up and remains. Combining the lake pounded ice layers with the splash and drips of water from the land makes a magical world of ice to explore. The interiors of the sea caves have formations that echo the stalagtites and stalagmites of the rock formations deep within a cave like Carlsbad Canyon. The sea caves have not been accessible by foot for several years now, and I fear, may also be one of those memories of the past on Lake Superior, with rapidly changing ice conditions on the lake.

One of my favorite Lake Superior ice memories was a winter quite a while ago, where ice had piled in deep layers at a friends house near Illgen City. We took our ski poles for stability, and for something to grab if the ice broke up! We hiked over the jumbled layers of ice in a fairly large area. It reminded me of a giant jello cube salad which various shapes frozen together into a very thick layer. The thickness of the layers was obvious because air pockets were captured periodically through the ice and it was easy to see that they were many feet down. It was very safe on that day except for the rough uneven slippery surface. But ice that blows in one day can quite frequently be totally gone the next. I have watched fishermen at the Lester River sitting on ice that was literally moving up and down, and wondered greatly about their sanity. My mother always said it takes all kinds.

But no matter what kind you are, I hope you can take some time and explore some of the ice formations around the shores of Lake Superior before these natural sculptures are gone for another winter. Happy explorations!

These updates are made possible by a generous donation from David and Rosemary Good.

 

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