Red Rock Wilderness Store's
Slush Primer 101

By Joe Baltich

There's always a big discussion about SLUSH in the wintertime on the lakes of northern Minnesota (and other areas as well).  Countless visitors who come to our area usually respond in mainly two ways when they ask why we don't recommend heading out willy-nilly across the lakes in the BWCA if you really and truly only do this sort of thing recreationally and only on occasion.   When we suggest that they reconsider due to slush, most responses we witness include either the "blank-stare-mouth-agape-head-slightly-cocked-to-one-side look" or the "Oh, of course - the lakes are "slushy" - we get that all the time in Minneapolis" look.  Well, this winter (2004) has been a horrendous slush year and I've explained it so many times to so many people, I've decided that it's just easier to put out some artwork together with this web page so folks can understand it better, hopefully.

Slush Defined
First of all, slush conditions in our neck of the woods is a bad thing never to be taken lightly.  Real slush, not "slushy conditions", occurs regardless of air temperature and does NOT and will NEVER occur from melting snow.  If the snow is melting and "slushy", nobody here even gives a half a hoot about it.  Real slush occurs when there's too much snow on top of the lake ice (see #1 below).  The weight of the snow pushes the ice down below the normal level surface of the water.  The ice cracks due to bending (see #2 below) and the water heads up through the crack(s) to where it wants to be which is back to it's normal surface level  (see #3 below).  The water doesn't care if there's a ton of fresh powder snow up there, it just has to get back to level.  As a result, it mixes with the snow usually in large pools on top of the ice but well below the top of that seemingly harmless, beckoning snow.  Think of that clean white snow as the beautiful mermaid and the slush would be the ship-eating rocks just under the surface.  As slush sits under the fresh, fluffy, undisturbed snow, it lies insulated from the -30 (and colder) degree temps and does not freeze until the snow on top of it has been compressed in some way.  The three main ways that snow can be compressed are by: 1. human/animal disturbance, 2. warming air-temps which cause the snow crystals to break down and the snow to settle which makes it lose its insulation quality,  and,  3. the heat from alien spaceship exhaust pipes which has never been proven, but the theory does have its believers.   For right now, go with reasons 1 and 2.  When the insulation layer is lost, the slush turns to ice and that's a good thing. 

Double Layers
Sometimes, slush freezes over but not all the way through to the main ice below.  That results in double-layered ice which spells a HUGE pain in the butt when you are ice fishing.  You drill though one layer of seemingly good ice, then hit 8" of water, then drill thru 10" of mushy ice.  This can make for better traveling, but sometimes, you'll experience the thrill (bad thrill) of breaking through the top layer of ice and dropping down to the next layer.  While usually not dangerous, it can scare the heck out of you initially and fill up your boots again with ice water which is not good.  There's something about getting a snowmobile stuck in double layer ice that changes your perspective on things, too.  Prepare to grunt, cuss and sweat.  When you drop the track through the top layer and the skis remain hung up on the top layer, it's really entertaining!

Air Holes
Meanwhile, the second significant problem resulting from slush conditions rears its even uglier head - air holes.  While loved by otters and beavers who've been holding their breath under the ice, air holes, are anomolies you really want to avoid on the ice.  LOTS of people just do not understand how dangerous air holes are and how unsafe they really can be.  Air holes occur when the ice which has been forced underwater by all that heavy snow tries to do what ice always does: float on top of water.  In water, ice floats (in pure alcohol ice sinks like a rock- so never accept a drink that has the cubes on the bottom of the glass) and the ice below the level surface of the water wants to get back to the top of the water. 

See real airholes here

As the ice floats upwards in a massive sheet, the water on top of the ice (in the slush) heads back under the ice via gravity to reunite with its liquid family. So, to do this, the water drains though a crack in the ice that again was caused by all this moving around by the ice.  As it pours through the hole, it spins in a whirlpool which erodes the ice into the air hole itself which can be quite big with a good sized radius of weak ice around it.  Eventually, this area will become exposed to the air and freezes up solid at which point it is usually safer to walk on, but you want to be really sure before you go messing around an air hole.  You can usually see air holes by noticing the indentations or dips they make in the snow and the darker color of the water.  If you could float over them and look down, some can appear to be in the pattern of a flower with diseased, deformed petals from where the water was running to the hole. Other air holes can be just a 6" diameter hole in the ice with the snow slumping slightly around them.  Occasionally,  wind-driven snow can crust over air holes and leave one with the impression that nothing dangerous lies ahead until it's too late.  People equipped with skis or snowshoes and a good dose confidence fueled by ignorance often go right up to the edge of air holes to see why that water is open. (!!!) We've witnessed oblivious people tracks many times and marvel that there's no solitary hat laying next to the hole with only the tracks leading one way up to the edge of the hole.  Skis, snowshoes and snowmobiles make for great ways for the oblivious to get in WAY over their heads.   Going through the ice with any such equipment attached to you, is a HUGE problem that most likely will end in catastrophe. 


Cold Feet
It should be obvious by now that you want to stay out of slush whenever possible.  People who don't know this fact, many times will try to head right through it with skis, snowshoes, snowmobiles and dog teams (hard on the poor dogs' paws!).  They usually end up with two 50 lb. ice-covered snowshoe on each foot, or a 50 lb. log (used to be a ski) on each foot, or with a snowmobile track and tunnel full of the "evil slurpy" making it bog down to a complete and total, unmovable, stop.  Your boots fill up with super-chilled ice water and you wreck your back just trying to move that machine out of there because it'll freeze solid over night now that you've exposed the water to the air by driving, walking, or skiing on it.  There's nothing better at producing a dangerous, bone-chilling, hypothermia-producing, sweat when you're stuck in real slush trying to get out at -25 real degrees F while your feet lose all feeling. (Sorry, I don't count windchill as real temperature, either.)  When somebody says slush around here, I always take it seriously and you should, too. 

What To Do
If you're paying attention and do hit slush, usually you can detect it and avoid it before it becomes a major problem. On any unfamiliar  lake, I always look for slush just by kicking the snow away down to the ice with my foot, and I monitor it along my way as well. You get into this habit without fail. It's something you learn when trying to put in ski trails over lakes.  If I see even a little slush, I go into slush-alert mode.  I haven't mentioned it, but to everything you've read thus far I can say "Been there, done that." with the exception of dog teams.  I'm not making this up and slush is really no big deal to those with hands-on experience who know to avoid it.  But, being inexperienced and oblivious will result in your getting bitten.  So pay attention to where you are going.  You'll see slush being very dark when you stick a ski pole in the snow, or the person following the lead guy on snowshoes will see it soaking up into the compressed tracks of the lead guy in a noticeably dark gray color.  Or, if the lead snowmobile is sending up a rooster tail of water and apparently slowing down quickly in front of you, that should be your clue.  At this point, don't continue onward, go back from whence ye came and try a different route. Take a look at a large area of the ice ahead of you and see if you can see the gradual, subtle, slump in the snow on the ice.  Depending on how the wind moved the snow around, this will not always be obvious or easy to see.  Try to stay on the ridge surrounding the slump in the ice and go around the slush. For slush conditions, I also recommend rubber bottom, leather top, insulated boots.  I'd avoid the more stylish footwear that's out there today if I suspected I was going to possibly hit slush somewhere out there. Water usually soaks right through the non-rubber footwear no matter how much silicon spray you apply.  Some of today's footwear is made just so you can look "special" and still have warm feet while out shopping in downtown Ely. It's great so long as the snow is dry and powdery, but you won't have what you need in wet, cold,  conditions.  If you're going to be in wet, freezing conditions, make sure you wear the right stuff.


How to get into a canoe properly Proper Canoe Unloading
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Last Revised -Feb. 16, 2004

Red Rock Wilderness Store
2267 Fernberg Road
P.O. Box 690
Ely MN  55731