Don’t Break The Ice! ... How Not To©

  

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Remember that classic old game, “Don’t Break The Ice?”, it was a lot of fun!  But breaking through the ice in real life isn’t, in fact it is downright deadly!

 

How do you know if the ice isn’t safe?  Ice is tricky and just because a lake or river is frozen, it doesn’t mean that it is safe.

 

According to the U.S. Army Cold Regions Research and Engineering Laboratory in New Hampshire, you can’t tell the strength of ice just by looking at it, the daily temperature, the thickness, or whether it is covered by snow or not.  Ice strength of ice is based upon a combination of the size of the water body, the water chemistry, the distribution of the of the ice, and local climatic factors, plus the depth of water under the ice.  Below are suggestions that these researchers have on what to look for to stay safe.

 

At the ice’s edge, look for areas of open water, signs of recent changes in water levels, such as the ice sloping down from the bank as the water level dropped, or wet areas because the water has risen and flooded ice that couldn’t float, because it was frozen to the bottom or the banks.  If the ice is covered in snow, look for wet areas in the snow.

 

Find an easy approach to the ice, free of cracks or piled, broken ice.  Whether you are walking or taking a vehicle out on the ice, first check it out on foot.  Using an ice chisel, strongly probe ahead of yourself.  

 

Near the shore, listen for hollow sounds while probing.  Ice sloping down from the bank may have air space underneath.  This is not safe; ice must be floating on the water to support weight.

 

If the ice chisel goes through, cautiously turn around and retrace your steps back to shore and try again another day or somewhere else.

 

Others in a group should follow in the leader's steps but stay at least 10 feet (3 meters) apart.

 

Drill or chop a hole through the ice and check the thickness every 150 feet (45 meters) or so along the intended path.  Ice seldom freezes or thaws at a uniform rate, and it can be a foot thick (30 cm) in one spot while, 10 feet away, only an inch thick (1 cm).  If the ice thickness is variable, check more frequently.

 

Measure the thickness and see if the ice in each hole is clear white, or grey ice.  

 

The strongest and safest ice is clear ice (also sometimes called blue or black ice), and typically forms at the start of the season on top of calm water.  This ice is clear but can appear blue or black, when looking down into the water.

 

White ice occurs when snow melts on top of a sheet of ice and then refreezes.  This type of ice is only about half as strong as new, clear ice because it is full of air bubbles and is made up of smaller crystals.  

 

Gray or “rotten” ice may appear transparent or splotchy grey and is a loose term for ice that is melting or being honeycombed with liquid water or air, it is generally found after spring or summer thaws.

 

Frozen lake or stream water will be stronger than ice formed by melting snow, refrozen ice, or ice made by water bubbling up through cracks in the ice and freezing on the surface.  

 

Remember, several inches of new ice may be strong enough to support you, while a foot or more of old rotten ice may not be. 

 

Measure the thickness of snow cover on the ice, different thickness of snow may mean different thicknesses of ice, because snow is a good insulator, slowing down the formation of ice.  Also, the weight of snow can decrease the carrying capacity of the ice. 

 

If the snow cover is heavy enough, the ice sheet will sag below the water level.  Then water will flood through cracks in the ice, saturating the lowest layers of the snow and making slush.  When the saturated snow/slush freezes, it will add a layer of white ice to the original layer of black ice.  However, until this slush freezes, stay off the ice sheet. 

 

River ice is dangerous and is about 15 percent weaker than lake ice.  On rivers, ice thickness and quality can change quickly due to bends, shallows, or tributaries.  The problem with rivers is that there is always water moving underneath the ice and no matter whether the current is slow or rapid, water can be pushed up from deeper depths, where the water is warmer, to the surface.  This creates thin spots, and once a person falls through, the current can carry you under the ice.  Straight, smooth flowing stretches are safer than river bends.  River mouths are dangerous because the incoming current undermines the ice and creates thin ice.  

 

For both rivers and lakes, warmer water from springs can create areas of thin ice.  The ice near shores can either be thinner, due to warm groundwater flowing in or the insulating effect of drifted snow, or thicker, because of the candle-dipping effect of changing water levels.  Ice near the shore is weaker, because the buckling action of the lake or stream continually breaks and refreezes ice near the shore.

 

If the air temperature has been above freezing for at least 6 of the past 24 hours, use the 1.3 lower dashed line on the graph to the right, obtaining a larger minimum ice thickness to account for any possible weakening.  If the air temperature stays above freezing for 24 hours or more, the ice starts losing strength, and the graph no longer represents safe conditions.  Stay off the ice!

 

You are likely to encounter cracks in the ice.  Cracks are either wet or dry.  If they are dry, they do not penetrate the ice sheet and are not a concern.  If they are wet, use the 2.0 upper dashed line on the graph to obtain the required minimum ice thickness.  The same for if you plan to leave a load on the ice for extended periods, more than two hours. 

 

If you cross wet cracks, your path should be as close to perpendicular to them as possible, instead of parallel to them.

 

And contrary to what you might expect, a rapid, large air temperature drop makes ice more brittle, and the ice may not be safe for 24 hours or more. 

 

If you hear ice “booming” or cracking on cold days or still evenings, it doesn't necessarily mean that the ice is dangerous, only that it's changing shape as the temperature changes.  On a lake larger than several acres such noises may be harmless responses to thermal expansion and contraction, however on a river this may mean the ice is about to break up or move. 

 

A potential danger spot on lakes is an open portion surrounded by ice.  Winds will force exposed water beneath the ice and rot it from below.  the actions of birds and fish can weaken ice, for example, schools of carp can create thin spots in the ice, or even open water, by schooling in one location moving the water with their fins, in effect creating a current.

 

So, if you are out on the ice this winter, remember don’t break the ice!

 

I hope that you enjoy learning from this resource!  To help me to continue to provide valuable free content, please consider showing your appreciation by leaving a donation HERE.  Thank you and Happy Trails!

 

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That is all for now, and as always, until next time, Happy Trails!

 

 

Sources

 

City of Corning Fire Dept; “The Dangers of River Ice”, [Corning, NY], https://www.cityofcorning.com/vertical/sites/%7BBE0E976C-81B9-4F4C-8763-A90E76CF4D33%7D/uploads/The_Dangers_of_River_Ice_2016.pdf, accessed January 4, 2025

 

McQueeney, Kerry; “Caught on camera: The terrifying moment girl plunges through ice into lake after being egged on by friends... and lives to tell the tale”, Daily Mail, February 15, 2012, [Associated Newspapers Ltd], https://www.dailymail.co.uk/news/article-2101030/Pictures-girl-falling-ice-lake-egged-friends.html, accessed December 28, 2024

 

Minnesota Department of Natural Resources; “Ice formations and conditions”, [© 2025 Minnesota DNR], https://www.dnr.state.mn.us/safety/ice/ice-formations-conditions.html, accessed January 4, 2025

U.S. Army Cold Regions Research & Engineering Laboratory;

“Safety on Floating Ice Sheets”, [U.S. Army Corps of Engineers, Hanover, New Hampshire], https://rivergages.mvr.usace.army.mil/WaterControl/Districts/MVP/reports/ice/safety.html, accessed January 4, 2025

 

U.S. Department of the Army; “Engineering and Design: Ice Engineering, EM 1110-2-1612”, September 30, 2006,  [U.S. Army Corps of Engineers, Washington, DC 20314-1000], https://www.publications.usace.army.mil/Portals/76/Publications/EngineerManuals/EM_1110-2-1612.pdf, accessed January 4, 2025