Lake Superior Ice Formations
A Look at the Diversity of Lake Superior Ice Formations
Most of us understand how lake ice forms. Water gets cold… really cold… and it turns to ice. Yet this (relatively) simple process combines with other forces of nature to create an astonishingly diverse “family” of ice formations. With our upcoming Winter Photography Workshop – and its focus on capturing the beauty of Lake Superior ice formations – I thought it might be fun to do a quick post on some of the different types of ice we’re likely to encounter.
The NOAA Great Lakes Environmental Research Laboratory (GLERL) studies the relationship between ice cover, lake temperatures, and regional climate using scientific models based on observations of variables, such as ice cover and surface water temperature. The amount of ice cover, as well as how long it remains on the lakes, varies greatly from year to year and can have all kinds of effects on the regional economy… the shipping industry, for example.
As you can imagine, lake scientists – like those at GLERL – have developed an “ice taxonomy” and that’s where I started.
Various Types of Lake Ice
Pack ice typically refers to large, free floating ocean ice sheets. This somewhat general term includes any form of floating ice that is not attached to the shoreline. Given that Lake Superior is basically an inland sea, we get our own pack ice. Yay! The Manual of Great Lakes Ice Forecasting (if you want to get super nerdy click HERE for more ice-related terminology) describes “cake” ice – basically detached segment of pack ice that are less than 50 feet in diameter – and “floe” ice – detached segments greater than 50 feet in diameter.
The term “brash” ice refers to much smaller pieces of ice floating in water and are often found along the edges of larger chunks of pack ice.
This is what we typically think of when we talk about ice formations along the shores of Lake Superior. Stack ice forms when lake ice breaks up and the wind is sufficient enough to push loose, broken ice pieces towards the shoreline. The wind, along with a bit of wave action, cause the ice pieces to pile on top of themselves in a vertical fashion.
Stack ice can form a “mosaic” which refers to piled ice cover where the individual ice pieces have been created and frozen together over a period of time. These ice piles typically have a “weathered” look to them due to their exposure to wind erosion.
Splash ice is really cool because it coats the shoreline… and anything on it… with a thick layer of ice that creates all kinds of interesting stapes. This type of ice forms near open water where waves are actively splashing onto the shore line. On large lakes, like Lake Superior, splash ice can form very large ramparts along the shoreline that make for some great winter photography.
These well-known ice hazards are somewhat common near the shoreline. Pressure ridges are wall-like formations of broken ice forced upwards by pressure. They typically from as ice warms and expands and the pressure from that expansion causes the ice to rupture.
Pressure ridges can pose a substantial danger – especially with vehicles on the ice. The ice along a ridge is typically composed of broken and often poorly attached pieces with little support below the surface. This makes pressure ridges a great winter feature to avoid.