The Satellite View

Image from Burlington NOAA website of Lake Champlain on December 28, 2010. At the time we were doing long distance skates on the southern end of the lake. Last year the Burlington NOAA office had the great idea of posting satellite images of the Lake Champlain Region from mid December through Mid April.   The images give good insight into the growth and decay of ice on Lake Champlain, northern Lake George and many other lakes in the area.  They also show what a snowy year we had last year.  Click here for an annotated slide show of the season with comments based on what we observed on the ground.   

 The original images and an explanation of how the images are taken can be found at .  

 The following is their cautionary note about the images:  

"Please note that ice may be clear or opaque in the pictures with a few apparently open water areas possibly having a thin, clear cover of ice. Thus, this page is intended as a reference source only, and those planning winter activities on the lake should make use of additional resources to determine more precise ice coverage and thickness in their area of interest."




Early Season Ice Checking

 For people on foot or with light sailing craft.

 A big, smooth sheet of new ice gives most of us ice fever.   Early season new ice is also some of the most unreliable ice.  This combination makes early season ice especially prone to swims.  The following is a general procedure for checking new ice.  You may need to adjust it for your specific situation and risk tolerance.   This procedure is intended for getting a feel for what hazards exist.  It is not comprehensive enough to find every hazard.   In general, if you find one hazard (like a new ice-hole) you can expect there are more of them elsewhere on the ice sheet.    It is recommended that your first few ice checking trips be with experienced ice checkers.  

Recommended equipment (in rough order of importance):

 Recommended preparation

  • Review the weather history for the previous week.  Pay particular attention to above freezing temperatures and wind when above freezing.  See if you can identify when the ice came in.  Snow falls are also important
  • If you can visit the lake a day or two  after the ice starts so come in,  you may be able to spot new ice holes and other open water  that may be thin ice later.
  • If you can find someone who spends a lot of time on the lake, ask them about persistent hazards.
  • Practice with your test pole (or other assessment tool) enough to get a sense of how it behaves on different ice thicknesses.
  • If it is above freezing, consider waiting until it gets colder. Sunlight can weaken ice quickly, especially in the spring. It also also can be much quieter than cold ice, robbing you of much of the cracking noise that reminds you that you are on dodgy ice. 
  • Arrange for a suitably equipped companion or two to accompany you. 

When you get to the ice:

  • Resist the temptation to check the ice if you are not fully prepared (eg:  you don't have your ice claws, friends, etc). 
  • Observe the ice as best you can from shore.  Look for open water,  jumbled ice, frozen ice edges, etc.  Binoculars and any a higher vantage point are both helpful.
  • Talk to anyone in the area who has been on the ice.
  • Use your test pole to test the ice as you move a little ways onto the ice and measure the thickness (knock a piece out with your pole, drill the ice, etc).  If it is 2" or less, come back when it is thicker.
  • If the ice is sufficiently thick (at least 2" and preferably 3 or 4"), walk or skate over the ice you want to check.  In particular look for open water, dark areas in the ice that could be recently frozen open water, wet cracks, gas holes, drain holes, etc.  Use your test pole a lot. 
  • Stress cracks can be a reasonable way to estimate the thickness.
  • Cracks that form as you move along should be considered a warning sign until proven otherwise.   Multiple cracks, especially with a circumferential crack a couple feet out, probably means you are in Wily E. Coyote territory.
  • Warm water holes and frozen ice edges account for a lot of early swims.   If you find frozen new-ice holes test their thickness.  All the holes may not freeze at the same time.
  • Frozen ice edges are best approached from the older/thicker side.  Typically the oldest ice is near the shore and at the back of bays.
  • Check snow drifts to see if they have thin ice or gas holes underneath.   Isolated gas holes will be hard to find if there are lots of drifts on the ice.  
  • If you are going to skate or sail after checking the ice, it is best if you mark problem areas.  Branches sticking out of holes, cones, flags, and Christmas trees have all been used.
  • After you have walked/skated on the ice you intend to sail on, start off by sailing slowly so you can recheck the ice.  In most cases you will cover a lot more ground when sailing than when ice checking.

Some hazards you might see:

  • New-ice holes
  • Early season gas holes (in new ice they can be hard to see.  If you see  bunches of marsh gas bubbles in/under  the ice, check the area carefully for thin spots)  More...
  • Frozen ice edges: As you approach one from behind you typically see a sequence of wave-break cracks, broken ice, jumbled ice, often a slush ice band around forms around the broken pieces.  A white splashout rim at the edge and, finally, dark new ice on the other side.  The new ice may be white from slush that the wind accumulated against the ice edge before it froze.
  • Wet cracks and leads, frozen or open
  • Pressure ridges (they usually don't show up until the ice gets 2-4" thick). Expect them to form across bay mouths, along shore and across the lake between points. Crossing ridges on thin ice is tricky...eiher wait for the ice to thicken find what appears to be a good crossing.  Don't linger on the weak parts of the ridge. 
  • If it has been warm expect drain holes and, possibly, puddle holes.
  • Thin ice associated with inlets, outlets, reefs, etc
  • Swamps and flowing water (rivers or  narrow places in lakes) are likely to have thin areas. 
  • If the top layer is snow ice (frozen slush) be especially careful.   Determine if the slush is frozen all the way through and expect that it might not be elsewhere on the ice sheet, especially under any dry snow.   If there is any question about the slush being completely frozen, make sure the underlying black ice is over two inches thick.  (more...)

 Lloyd Roberts wrote an excellent article on ice checking in the NEIYA newsletter.  In my opinion his minimum thickness recommendation make his approach oriented to more experienced ice checkers with a relatively high risk tolerance.  (Click Here)

 Eric Anderson talks about the checking for DN sailing near the beginning of his article on clothing.  (Click Here)

 One last thought:  When you report on what you find, make sure your ice fever is not talking.  You will  quickly get a bad reputation if you tell people the ice is better than it is.  Stick to what you found and what hazards you have good reason to suspect.  Give an idea of where you looked and where you did not.  Along the same line of thinking, take all ice reports with a grain of salt until you have checked the ice yourself.  Even with a good report, the ice may have evolved between the time the check was made and when you get to the ice.



How Thin is Too Thin?


Note: This blog post has become a more complete page on the subject of thin ice.  Click here to go to the new page.

There are two aspects of deciding if the ice is barely thick enough to support a person on foot.

1) Is the ice under your feet strong enough?

2) How confident to you want to be that all the other ice that you are going to walk on will be strong enough?

Human Ice Tester (the author) lounging in an area broken up by testing. With 3 layers of long underwear inside the dry suit and a bit of exercise, it is comfortable in the water even with 20 deg air temperature.  

Based on a few experiments on thin black ice over shallow water, 175 lbs will probably break through 1.1" (28 mm) but probably won't break through at 1.2".  At 1.1", it looks like you should be able to get back on the ice in a prone position.  If it is much thinner you can't!  If you are on skis, a light iceboat or even skates you can get far out on ice that will be too thin to get back on. 

 The second question, about the acceptable level of risk of falling through, is a little harder to answer.  Ice thickens quickly when it is thin so there are likely to be local differences in when it caught and how fast it grew, resulting in variable thickness.  Thin ice often has very few cracks to give an indication of thickness.  Thin ice is dark so there is not much contrast between ice that is thick enough and ice that is not.  Also, white splash-out rims may not have developed around any holes.  This makes recently skimmed over holes especially hard to spot.  In general, ice thinner than two inches is more likely to have these issues and even much thicker ice often has areas of open water or thin ice.   

 Ice Testing: A test pole  is the best way for a person on foot to test ice thickness for ice less than three inches thick  (nordic skating poles, ice chisel, wood test pole).  A pole is better than a drill as you can assess ice quickly and easily making it more likely to be used enough.  Axes are popular in some areas.  They are effective but are not as fast as a pole and they have a shorter handle.    To properly measure ice thickness requires a tape or other scale.  1/8" accuracy matters.  You can't get a good enough measurement by eye.  You can measure at wet cracks, or recently refrozen ones opened by your test pole, fishing holes, a hole you drill or by knocking a piece of the plate out with your test pole.  A single hole made with a test pole usually has a cone knocked out of the bottom of the ice sheet, making it hard to use for making an accurate measurement.

 Cracking:  A single crack that forms as you move over the ice may or may not mean it is too thin.  Single cracks that follow you can occur in fairly thick ice that is under some stress.  None the less, any cracking that appears to be related to you is cause to verify the ice thickness.   If you are starting to see or hear cross cracks (zipper cracks) or to see double cracks going in your direction, you are probably pushing the envelope.  This is a great time to have on a dry suit, a life jacket and a rope between you and a buddy on thick ice nearby (or, even better, to be doing something else while you wait for the ice to get thicker).   

 Shallow Water: The notion of staying over shallow water is reasonable but you may get just as wet if you break through.  If you are on something that spreads your weight enough to get you far out on thin ice before you break through, you could still be in big trouble even though it is not over your head.

 Reasonable Thickness: On ponds we know well, with full equipment (claws, test poles, ropes, clothing, floatation, etc), we will skate, with some trepidation, on subfreezing  2+ inch black ice and sail DN's on 3".  So far we have had relatively few problems at that thickness.    Over the years, we have had plenty of swims in the thinner areas that can often be found somewhere.  On bigger ice or with less experience or less equipment or less risk tolerance, adding an inch or two or more to these numbers is prudent.    

 For a range of activities the Minnesota DNR recommendations for good black ice at temperatures below freezing are reasonably conservative.   The strength of thawed ice is significantly less than when it is below freezing.  Without a significant warm wind, the thawing process takes place mostly internally at the crystal boundaries so the thickness may not change much as it thaws and gets weaker. Ice less than a few inches thick thaws quickly: a couple hours might be enough.  Even early in the thaw process it can lose 50% or more of its strength. In thick, highly thawed, small grain ice we have seen situations where it has lost 99% of its original strength.    Snow ice gets particularly weak in thaw conditions as it turns to mush.

Click here for a Swedish video of part of the standard training procedure for skaters:  finding out what it is really like to fall through thin ice. There are a bunch of these videos.   They give a decent idea of what it is like to fall in at low speed, how getting back on the ice goes, etc.




Skate Sailing on Lake Champlain

By Daan Zwick

 As a fourteen-year-old Burlington boy in 1936 I was greatly attracted in the winter by the huge expanse of ice that was Lake Champlain.  By the middle of January the ice was usually solid all the way across to New York State, and a village of hundreds of fishing shanties, each set on top of a hole that had been chopped through the ice to receive fishing lines, had arisen in Burlington Bay a few hundred yards from shore. 

 Lake Champlain off Burlington

Farther out, ice boats would be skimming swiftly about, their large sails rising from low wooden platforms set on two long widely-set runners.

I have never had such a sensation of speed as I experienced while lying on such a platform about six inches from the ice, skimming along at forty miles per hour.

   Right near shore, north and south of Burlington, there would be areas marked out as hockey rinks with crude goals at the ends.  Later in the season, farther from shore, there would be large rectangles bounded at the corners by old Christmas trees, marking areas from which blocks of ice had been cut for commercial purposes, indicating those dangerous areas of thin ice or open water.

 The lake would freeze in huge sheets, smooth and even for hundreds of yards, separated by cracks caused by the expansion of the freezing water.  Those cracks were not very large, and the water in them froze also, leaving just a rough place for skaters to jump over and ice boaters to rumble across.  Only occasionally would there be a layer of snow on the ice that would prevent easy skating - strong winds usually blew the cold dry snow off the smooth surfaces.

I found in my Boy Scout handbook a reference to a pamphlet that showed how to construct a sail for skating.  I sent my twenty cents to buy that - one of my best investments ever.  The major ingredients I had to buy were two hickory poles, one 8-feet-long for a mast and the other7 feet long for the boom, and a thinner nine-foot ash pole.  I had to steam this pole to make it curved for the top of the sail frame.  The boom was lashed at its center by a leather thong to the mast about five feet from one end.  The long curved ash pole was centered on the mast and bent to meet the ends of the boom to forge the top of the kite shape    I laid this frames on a big sheet of unbleached muslin, as a pattern for a kite-shaped sail that I cut out and attached to the ends of the mast and boom, using a cord around its perimeter. 

 A modern edition of Daan's skate sail on Canyon Ferry MT, Photo by Viki Gluek

To sail, I pulled the kite up vertically with the boom across my shoulder on the windward side, and leaned against the wind, turning my body in the direction I wanted to go.  To stop I just lifted the sail over my head and held it horizontally.  Then I could come about by dropping the sail on my other side, and leaning that shoulder against the wind.  I found that I had to buy a pair of 18-inch racing skates – regular hockey skates did not have enough bite on the ice to allow me to sail into the wind.

 The pamphlet also described making and using a handy safety device.  I purchased two short hand-held ice picks or augers, screwed a hook-eye into the end of each handle, and connected them by a five-foot cord.  I carried one in each jacket pocket.  The purpose was that if I fell through the ice, the picks would be readily available to grab, one in each hand, to enable me to stab them into the ice, to climb back up onto the surface of the ice.  I always carried them, but I never had to use them.

 The sail made skating on the lake easy and exhilarating.  Instead of fighting the wind, I was using it, so I could go farther and faster than mere skating would allow.  However, the lake was always bigger and stronger than I was.  I never went as far as I had hoped to.

 Daan Zwick  6/20/11

Note: See the previous blog entry for a little background on Daan




Tragedy on the Lake

The Green Mountain Club (GMC) founded, built, and maintains Vermont's Long Trail, which was the first long-distance hiking trail in the United States. The Long Trail runs  270+ miles from the Massachusetts state line to the Canadian border. The author of the following story has been a GMC member for decades and has donated thousands of volunteer hours as a caretaker for some of Vermont’s highest peaks and most picturesque trail shelters. 


Burlington Section Skating Trip of 1937

By Daan Zwick

In the first half of the twentieth century Lake Champlain always froze over solidly during the winter months.  (Roy Buchanan averred that the lake had frozen over every year within anyone’s memory, except in 1888.  That year  the frantic swimming of a whale that had been trapped in the lake kept the lake from freezing.)  Skating, ice boating, and ice fishing were popular recreations, and ice harvesting was a profitable industry. Hundreds of seasonal fishing shanties appeared on Burlington Bay, Mallets Bay and Shelburne Harbor.


In the winter of 1937 Larry Dean led six Burlington Section members on an outing  intending to skate across the lake at its widest point to New York State and back, a total of 26 miles.  The surface was vast sheets of smooth, snow-free ice separated by an occasional expansion crack.  I came across a disk of ice about like a hockey puck and decided to see if I could kick it ice with just my skates all the way to New York.  In so doing I got separated from the rest of our small group.  After a couple of miles of that effort my ice puck had disintegrated, so I gave up and went to rejoin the group, which I had seen in the distance near Juniper Island.

 Lake Champlain at Burlington. The blue mark is just north of Juniper Island. The yellow one is at the South Burlington shore. The blue line is a mile long (for scale)

On my way to that island I met a boy struggling to skate under the load of a limp girl.  I asked if I could help him.  He said that some kids playing on the ice near the island had fallen into the frigid water, and the girl was one of them.  He was trying to get her to shore, but he was tired.  I could see that the girl, probably nine or ten years old, was wet and shivering, so I took off my jacket and put it on her.


I slung the girl across my shoulders and headed for the South Burlington shore as quickly as I could skate with that load.  I could feel her shivering as I carried her so I changed my plan and stopped at the first fishing shanty out on the ice that had a stovepipe. Finding it inhabited and very warm inside, I left my passenger there with the fisherman to get warm while I skated to the South Burlington shore for more help


There I found that an ambulance had come, so I directed the crew to where the girl was. There was also a doctor waiting on the shore – he was the medical examiner who had been called to go out to Juniper Island to declare a drowned child legally dead, but he was not up to the two-mile trip across the ice to Juniper Island. 


I scrounged around and found a small sledge with ice runners and a handle in back – just the thing to transport the doctor.  As I started out from the shore, a reporter from the Burlington Daily News tried to jump on the sled, but I pulled him off – the doctor was as much load as I could handle.  Reaching the island I waited until the doc had performed his duties and then transported him back to shore.  By that time my ankles were so tired I could skate no more.


(I learned later that a family of four children from the shore nearby had gone with their sleds to play on Juniper Island.  While the open lake ice was very thick, and safe for travel, the south side of that rocky island had absorbed enough of the sun’s heat to weaken the ice there so that the children had broken through.  One boy in that group had managed to pull all his siblings to shore on the island, and holler for help.  Larry Dean, who had led his group past the north side of the island just a few minutes before, heard the call and responded. For a long while Larry performed the prone pressure rib compression resuscitation (state of the art first aid at that time) on the one child who was not breathing.  In spite of his effort, Larry was not successful in restoring life to the boy – thus the call for the doctor.


I do not know if there ever was another Burlington Section attempt to skate across the lake.


Daan 3/31/11

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