Exploring the wilderness in winter is a wonderful experience. You
are far from the crowds, in a hushed tranquil world of white.
Whether gliding through a glade of maple trees on cross-country
skis, hiking up a ridge on snowshoes, or ice climbing, winter can be
a spectacular time of year.
At the same time you must realize that this environment can be
extremely dangerous. It takes proper trip planning, experience, and
the right equipment to travel safely in the winter environment. If
you aren't aware of the hazards you can be at great risk. This
article will help you understand how to travel in the winter
wilderness. The greatest dangers in the winter environment are
hypothermia and frostbite. These are covered completely in the
Hypothermia and Cold Weather Injuries article.
Planning a trip in the winter means spending a good deal of time
researching areas and conditions to determine where, when, and how
the trip will work. All of these factors will interact to determine
what your daily pace and mileage can be.
- Goals for the trip
- Route - will you be on a trail of off trail, or a mix
- Snow level - shallow or deep
- Snow quality - powder, packed, breakable crust, or variable
- Trail - breaking trail or on a broken trail
- Mode of travel - will you be hiking, snowshoeing, or skiing
- Elevation changes - going up may be very slow while coming
down may be very fast
- Strength and experience of group
- Group size
Keeping all these factors in mind, set up a Time Control Plan for
your trip. Keep in mind that everything takes "twice" as long in the
winter (setting up camp, breaking camp, cooking, going to the
bathroom, etc.). Look at your proposed route for potential campsites
for each day. Also look to see where you could camp before your
planned site if you can't make it. Know what your emergency and bail
out options are if conditions deteriorate or you have problems. Talk
to area rangers about permits and camping restrictions. Find out
about snow levels, avalanche danger, safety of ice crossings, etc.
The essence of staying warm in the winter is having the proper
clothing layers and knowing how to use them effectively.
The body basically acts as a furnace, producing heat through
chemical reactions and activity. This heat is lost through
conduction, convection, evaporation, radiation, and respiration. As
physical activity increases so does heat production and conversely
as activity decreases so does heat production. The key to keeping
warm is to add insulation to the body.
The thermal insulation of clothing is proportional to the
thickness of the dead air space enclosed. Dead air is defined as any
enclosed unit of air that is small enough that natural convection
currents would not arise in it. Such currents have been detected in
units as small as 2 millimeters in diameter. The dead air next to
the skin is heated up by the body and provides a layer of warmth
around the body. The clothing is not what is keeping you warm it is
the dead air. This is because the denser a material the faster it
can transfer heat through conduction, the density of air is
obviously minuscule compared to a piece of a fabric. The "clo" unit
was developed to provide a measurement of insulating effectiveness.
One clo is roughly equal to the insulating value of an ordinary wool
business suit. Each inch of thickness of conventional insulating
materials (wool, pile, down) provides a theoretical value of about
4.7 clo or a practical "in use" value of 4.0 clo.
The Layering Principle
The key to providing this dead air space is through having a
number of layers of clothing. Each layer provides a certain clo
value of dead air space. This allows you to add or shed layers to
increase or decrease your accumulated dead air space as the
temperature changes and/or as your activity level changes. Remember,
your body is the heat source, the clothing layers only serve to trap
the heat and slow down your heat loss to the cold environment. If
you have too much clothing on, you will overheat and start to sweat.
You need to find the proper heat balance between the number and
types of layers and your activity level.
Example 1: You are snowshoeing up a steep incline with a 50 lb.
pack. The air temperature is 10o Fahrenheit and you are dressed in
wool pants and a lightweight polypropylene shirt. As soon as you
stop for a rest, your heat production slows. If you stop for more
than a couple of minutes, you will begin to chill. So you need to
have an outer layer handy to put on.
Example 2: You are skiing along the flat. The air temp is 25o
Fahrenheit and you are dressing in light polypropylene tops and
bottoms, a down vest, and a windshell. You come to a long steep hill
and have to push hard to get up and over. You start to sweat as your
heat production increase with the increased muscle activity. To
prevent overheating, you pull off the vest and stick it in your
Why not just have lots of layers on and sweat? Heat loss from a
wet surface can be up to 25 times greater than a dry surface (due to
the higher density of water). If you sweat and get soaked, you will
lose heat much more quickly through evaporation of the water. Also
you are loosing an incredible amount of water through sweating since
the air is so dry. Too much water loss leads to dehydration which
significantly increases the risk of hypothermia. So you want to
control your layers so as to be warm at the activity level you are
in but not sweating profusely.
Thus, traveling in the winter is a constant process of
adjusting your layers to keep comfortable. This means having a
number of layers you can add or subtract and allowing for
versatility within layers. Convection may account for the greatest
amount of heat loss under most conditions. In order to properly
insulate, you need to have an outer layer that is windproof.
Example 3: You are standing on a windblown summit in a wool
sweater, the wind will penetrate through the openings in the sweater
and quickly carry away the warm layer of air next to the skin.
Another convective factor is the "bellows action" of clothing. As
you move a bellows action occurs which tends to pump your
accumulated warm air out through openings in your clothing and sucks
the cooler air in. In some conditions this action can reduce your
body's personal insulation by 50% or more. Thus, it is important
that all layers have effective methods of being "sealed"
(i.e. buttons, zippers etc.) Openings in layers allow you to
ventilate, to open the "chimney damper" if you are beginning to
overheat, without having to actually remove a layer. So opening and
closing zippers on a jacket, or armpit zips will allow you to either
ventilate if you are getting too hot or seal up if you are getting
chilly, all without having to add or take off a layer. With clothes
that are too loose, the bellows action pumps warm air out through
the openings. You need to have clothes that fit properly but not
tightly. Too tight, and the clothes compress and actually reduce
dead air space in layers below as well as restricting body movement.
Another general rule is that the efficiency of clothing is
proportional to the diameter of the body part it covers. Thus a
given thickness of insulation added to your trunk will be more
thermally efficient than the same thickness added to your arm or
leg. It will also help maintain that body core temperature. This is
why vests work well to maintain body heat. There is an optimal
thickness of insulation for each body part. Beyond that the added
bulk tends to be more of a hindrance in movement than the added
insulation is worth.
Have you ever noticed that your hands feel colder after putting
on a thin pair of gloves? This is because when insulation is wrapped
around a curved surface, the cross-sectional area of the insulation
through which the heat may flow is greater as is the surface area
from which the heat may be lost. This means that the total
insulation efficiency of a given thickness progressively decreases
as curvature sharpens over a surface. In addition, small cylinders,
such as fingers, show a paradoxical effect. The addition of a thin
layer of insulation actually increases heat loss until a thickness
of about 1/4 inch is reached. This heat resistance gains as
additional thickness is added. However, added thickness beyond 1/4
inch increases warmth very little in proportion to its thickness.
This is one reason that thin gloves don't keep your hands
Some of the different types of materials for winter clothing and
insulation are discussed below.
1. Wool - derives its insulating quality from the elastic,
three-dimensional wavy crimp in the fiber that traps air between
fibers. Depending on the texture and thickness of the fabric, as
much as 60-80% of wool cloth can be air. Wool can absorb a fair
amount of moisture without imparting a damp feeling because the
water "disappears" into the fiber spaces. Even with water in the
fabric wool still retains dead air space and will still insulate
you. The disadvantage to wool is that it can absorb so much water
(maximum absorption can be as much as 1/3 third the garment weight)
making wet wool clothing very heavy. Wool releases moisture slowly,
with minimum chilling effect. Wool can be woven in very tight weaves
that are quite wind resistant. An advantage to wool is that it is
relatively inexpensive (if purchased at surplus stores). However, it
can be itchy against the skin and some people are allergic to it.
2. Pile or Fleece fabrics - is a synthetic material often
made of a plastic (polyester, polyolefin, polypropylene, etc.). This
material has a similar insulative capacity as wool. Its advantages
are that it holds less water (than wool) and dries more quickly.
Pile is manufactured in a variety of different weights (thicknesses)
offering different amounts of loft and insulation. This allows for
numerous layering possibilities. The disadvantage of pile is that it
has very poor wind resistance and hence a wind shell on top is
almost always required. Versions of pile are available that have a
middle windproof layer.
3. Polypropylene and other Hydrophobic fabrics -
polypropylene is a synthetic, plastic fiber which offers dead air
space and a fiber which cannot absorb water. The fiber is
hydrophobic so it moves the water vapor away from the source (the
body). Polypropylene layers are extremely effective worn directly
against the skin as a way of keeping the skin from being wet and
reducing evaporative heat loss. As the water moves away from the
body it will evaporate, but each additional millimeter of distance
between your skin and the point of evaporation decreases the amount
of body heat lost in the evaporative process. Some fabrics rely on
the chemical nature of the fiber to be hydrophobic. Others fabrics
use a molecular coating the achieve the same end.
4. Vapor Barrier Systems - another way to stay warm in the
winter is through vapor barriers. The body is always losing water
through the skin even when we are not active. This loss is known as
insensible perspiration and occurs unless the air humidity is 70%.
This insensible perspiration goes on at the rate of nearly half a
quart every 24 hours. Since it takes 580 calories per gram to turn
liquid water into water vapor, heat is continually lost through
insensible perspiration as well as through sweat from any activity.
A vapor barrier is a clothing item which is impervious to water
thereby serving as a barrier to the transportation of water vapor.
When worn near the skin it keeps water vapor near the skin.
Eventually the humidity level rises to the point where the body
senses a high humidity level and shuts off insensible perspiration.
This prevents evaporative heat loss and slows dehydration.
Vapor barriers should not be used directly against the skin
because any evaporation of moisture directly at the skin surface
leads to heat loss. Wearing polypropylene or some other hydrophobic
layer between the skin and the vapor barrier allows the moisture to
be transported away from direct skin contact. There is no doubt that
vapor barrier systems are effective for some people in some
conditions. The issues you must consider before using a vapor
barrier are activity level, amount you naturally sweat, and
"moisture comfort." If you are not active, such as when using a
vapor barrier liner at night in a sleeping bag, the system will work
well. A vapor barrier sleeping bag liner will typically permit you
to sleep comfortably in temperatures 10 - 15 degrees colder than in
the bag alone. However, some people find that they are not
comfortable with the level of moisture in the bag and fell clammy.
If this interferes with sleeping it may be a problem, better to have
a better insulated sleeping bag. Vapor barrier liners for sleeping
bags also help in another way. In cold conditions, the moisture from
your body escapes upward through the bag, when reaching the cold
outside of the bag it condenses into liquid or event frost. Over a
number of days this moisture level in your bag increases. If you
can't dry out the bag it will slowly get heavier and heavier as it
holds more water. With a down bag, this moisture can actually soak
the feathers and cause the bag to loose significant amounts of loft
(dead air space), thereby reducing it's effectiveness.
When you are active, like snowshoeing, and you are wearing a
vapor barrier such as a vapor barrier sock, you must carefully
monitor how you sweat. If you are someone who sweats a lot with
activity, your foot and polypropylene liner sock may be totally
soaked before the body shuts down sweating. Having this liquid water
next to the skin is going to lead to increased heat loss. If you
don't sweat much, your body may shut down perspiration at the foot
before it gets actually wet. This is when the vapor barrier system
is working. The important point is that heat loss comes from water
changing state from a liquid to a gas. Liquid water next to the skin
leads to significant heat loss. Water vapor next to the skin does
not. You must experiment to determine if vapor barrier systems will
work for you.
5. Polarguard, Hollofil, Quallofil and others - these are
synthetic fibers which are primarily used in sleeping bags and heavy
outer garments like parkas. The fibers are fairly efficient at
providing dead air space (though not nearly as efficient as down).
Their advantages are that they do not absorb water and dry fairly
quickly. Polarguard is made in large sheets. Hollofil is a fiber
similar to Polarguard but hollow. This increases the dead air space
and makes the fiber more thermally efficient. Quallofil took
Hollofil one step further by creating four "holes" running through
6. "Superthin" fibers - Primaloft, Microloft,
Thinsulate and others - the principal behind these synthetic
fibers is that by making the fiber thinner you can increase the
amount of dead air space. For example, take an enclosed space 5
inches wide and place 2 dividers into that space, each 1 inch thick.
You have an effective air layer of 3 inches. If you take the same 5
inch space and divide it with 4 dividers, each 1/4 inch thick you
now have an effective air layer of 4 inches. You have gained one
inch. Under laboratory conditions a given thickness of Thinsulate is
almost twice as warm as the same thickness of down, however, the
Thinsulate is 40% heavier. Thinsulate is made in sheets and
therefore tends to be used primarily for outer layers, parkas and
pants. New materials such as Primaloft and Microloft are superthin
fibers that are close to the weight of down for an equivalent fiber
volume. They are now being used in parkas and sleeping bags as an
alternative to down. They stuff down to a small size and have
similar warmth to weight ratios as down without the worries about
7. Down - feathers are a very efficient insulator. They
provide excellent dead air space for very little weight. The major
problem with down (and it can be a major problem) in the winter is
that down absorbs water. Once the feathers get wet they tend to
clump, and lose dead air space. Using down items in the winter takes
special care to prevent them from getting wet. For example, a vapor
barrier sleeping bag liner in a down bag will help the bag stay dry.
Down is useful in sleeping bags since it tends to conform to the
shape of the occupant and prevents convection areas. Down is very
compressible, which is an advantage when putting it into your pack
but also realize that your body weight compresses the feathers
beneath you and you need good insulation (foam pad, etc.) underneath
you, more so than with a synthetic bag. Some people are allergic to
down. The effectiveness of a down bag is directly related to the
quality of the feathers used. Since down is made of individual
feathers, sleeping bags are garments must have baffles sewn in to
prevent the down from shifting in the bag which would create cold
8. Radiant Barriers - some portion of body heat is lost
through radiation. One method of retaining this heat is through use
of a reflective barrier such as aluminum. This is the principal used
in "Space Blankets" and is also used in some bivy sacks and sleeping
Note: Cotton is basically useless in winter time. It wicks water,
but unlike polypropylene, cotton absorbs this moisture and the water
occupies the space previously occupied by dead air. This means a
loss in dead air space, high evaporative cooling, and a garment that
is almost impossible to dry out.
The Body and Clothing
1. Head - because the head has a very high surface to
volume ratio and the head is heavily vascularized, you can lose a
great deal of heat (up to 70%) from the head. Therefore, hats are
essential in winter camping. The adage - if your toes are cold, put
on a hat - is true. A balaclava is particularly effective and
versatile. A facemask may be required if there are high wind
conditions due to the susceptibility of the face to frostbite.
2. Hands - mittens are warmer that gloves because you
don't contend with the curvature problem described above. Also the
fingers tend to keep each other warm, rather than being isolated as
in gloves. It is useful to have an inner mitten with an outer shell
to give you layering capabilities. Also "idiot strings" are
important to keep you from losing mittens in the snow. However,
gloves are always essential as well in winter because of the need
for dexterity in various operations.
3. Feet - finding the right footgear depends a great deal
on the activity you are involved in as well as temperature and
environment. The two general modes of travel are skiing or
snowshoeing (in areas with only a few inches of snow you can hike in
- Cross-country skiing - you need a boot that has
some ankle support due to the extra weight of a backpack. Also you
may need a ski overboot to give you additional insulation over the
- Snowshoeing/Hiking - regular backpacking boots
are not sufficient. They simply do not provide the
necessary dead air space. The options for boots
- Insulated Boots - such as Sorels or "Mickey Mouse"
boots. These are rubber or leather and rubber boots that use a
layer of wool felt to provide dead air space. The Mouse boots can
be Army surplus or modern copies (avoid the copies since they are
often poorly made). With the true Army boots, the black boots are
rated to -20 degrees and the white ones to -40 degrees. The one
drawback with Sorels is that the wool felt liner is exposed.
Breaking through a frozen stream may soak the liner which will be
difficult to dry. They can be used with snowshoes, crampons and
skis (with special bindings).
- Plastic Mountaineering Boots - plastic shell
mountaineering boots use inner boots made with wool felt or a
closed cell foam insulation. These can be very warm and easily
used with ski bindings, crampons, and snowshoes. Depending on the
inner boot, you may need insulated overboots to add enough
insulation to keep your feet warm.
- Mukluks - one piece moccasins which reach to the knee.
They are used with felt liners and wool socks. The Mukluk itself
serves as a high gaiter. They are flexible and breathable. They
work with snowshoe bindings and can be used on cross-country skis
with special bindings (Berwin Bindings) and with hinged crampons
(not for technical ice). They are extremely comfortable, but since
they are not waterproof they are best used in dry cold winter
settings where water and rain are not a problem (e.g. stream
crossings, possibility of rain, etc.)
- Heavy leather mountaineering boots with an insulated
overboot - this can be effective but the system still is not very
thermally efficient and may lead to frostbite of the feet (not
- Socks - one of the best systems for keeping feet
warm is using multiple layers. Start with a thin polypropylene
liner sock next to the skin to wick moisture away followed by 1 -
2 pairs of wool or wool/nylon blend socks. Make sure the outer
socks are big enough that they can fit comfortably over the inner
layers. If they are too tight, they will constrict circulation and
increase the chances of frostbite. Keeping your feet dry is
essential to keeping your feet warm you may need to change your
socks during the day. Foot powder with aluminum hydroxide can
help. High altitude mountaineers will put antiperspirant on their
feet for a week before the trip. The active ingredient, aluminum
hydroxide will keep your feet from sweating for up to a month.
(Some medical research has suggested a link between aluminum and
Alzheimer's Disease but small exposure [as of the original writing
of this article] does not appear to be a problem).
- High Gaiters - are essential for winter
activity. They keep snow from getting into your boots and keep
your socks and pants legs free from snow.
- Insulated Booties - these are booties insulated
with a synthetic fill that typically have a foam sole to insulate
you from the ground. They are very nice to have to wear in your
sleeping bag at night.
- Camp Overboots - are shells with an insulated
bottom. These can be worn over insulated booties for traipsing
around in camp. Also for those middle of the night visits to the
4. Outer Layer - it is essential to have an outer layer
that is windproof and at least water resistant. In some cases it may
be best to have the garment waterproof. It also needs to be able to
be ventilated. There is a big trade off between waterproofness and
ability to ventilate. A completely waterproof item will keep the
water that is moving through your other layers trapped, adding to
weight and causing some heat loss. However, in wet snow conditions,
if the garment is not waterproof it can get wet and freeze. Gore-tex
and other similar fabrics provide one solution. These fabrics have a
thin polymer coating which has pores that are large enough to allow
water vapor to pass through but too small to allow water droplets
through. Nothing is perfect, however, and although Gore-tex does
breathe, it doesn't breath as well as straight cotton/nylon blends.
If you opt for a straight wind garment, 65/35 blends of cotton and
nylon work well. The other approach is to have a waterproof garment
with sufficient ventilation openings to allow water vapor to escape.
This provides the ability to work in wet snow without worrying about
getting the garment soaked. Part of the basis for making the
decision is the area and you are traveling in. If you are in the dry
snow of the Rockies you needn't worry so much about waterproofness.
If you are in the northeastern mountains where freezing rain is a
possibility or very wet snow, you need to be prepared to be wet.
5. Zippers - are wonderful accessories for winter
clothing. Having underarm zippers on jackets can greatly increase
your ability to ventilate. Having side zippers on pants can allow
you to ventilate and to add or subtract a layer without taking off
skis or snowshoes.
6. Miscellaneous - knickers with knicker socks can make a
good combination. You have the option of ventilating by opening up
the bottom of the knickers and/or rolling down your socks. Also bibs
are helpful (both pile and outer waterproof layer) because they
prevent cold spots at the junction between tops and bottoms.
Underwear is also available in the traditional union suit design
which accomplishes the same thing. Snaps on jackets etc. can be a
problem because they fill with snow and ice and fail to work. Velcro
works much better as a closure.
- When you first get up in the morning (and at the end of the
day in camp), your activity level will be low as will be the
temperature. You will need to have many, if not all, of your
layers on at this point until breakfast is over and you have
started to become active.
- When you get ready to be active, you will need to take off
layers since you will begin generating heat. A good rule of thumb
is to strip down until you feel just cool, not chilled just before
activity. Failure to do this will mean overheating, sweating,
losing heat and you will have to stop in 10 minutes down the trail
anyway to take layers off. Open or closing zippers, rolling
sleeves up or down, taking a hat off or putting one on will all
help with temperature regulation.
- If you stop for more that a few minutes, you will need to put
on another layer to keep from getting chilled. Keep a layer close
- Whenever you get covered with snow, either from a fall or from
dislodged snow from a tree, it is essential to brush yourself off
to keep your clothing free of snow. Failure to do this often
results in the snow melting into your clothing and refreezing as
- At the end of the day, as activity decreases and temperature
drops, you will need to add layers. Once you start to cool down it
takes a lot of the body's resources (calories) to heat up again so
layer up ASAP before you get chilled. It may be good to put on
more that you think you need; it will only get colder. If you are
too warm, you can open up layers and ventilate to reach the proper
Internal versus. External Frame: Internal frames
tend to be better for winter use. They have a lower center of
gravity and hug your body better. When skiing or snowshoeing, the
weight moves more with your body allowing for greater freedom of
movement. This is especially important when you are on skis.
External frame packs have a higher center of gravity and tend to
swing a lot, sometimes throwing you off balance.
In order to carry all the winter gear for a multi-day trip (large
sleeping bag, lots of clothing layers, tents, lots of food and fuel,
etc.) you need a pack with a capacity of 5,000 cubic inches or
Sleeping bags for winter camping should be rated to temperatures
below what you will likely experience if you want to be comfortable.
If the nighttime temperature can drop to -15o Fahrenheit, then your
bag should be rated to -30o Fahrenheit. There are a variety of
different fills for sleeping bags: down, Primaloft, Microloft,
Qualofill, Polarguard, etc. The bag itself should be a mummy style
bag with a hood. It should also have a draft tube along the zipper
and a draft collar at the neck. In sleeping bags, you want the bag
to snugly conform to your body. If the bag is too big, you will have
large spaces for convection currents and you will be cold. In a bag
that has too much space, you may need to wear clothing layers to
help fill up the space. You can opt for the expedition bag which is
rated to -30o Fahrenheit or you can use a three season bag rate
rated to 0o Fahrenheit and augment it with a vapor barrier liner
(adds 5-10 degrees), a bivy sack (adds 5-10 degrees), and/or an
overbag (a summer weight bag that fits over your mummy bag - adds 15
- 20 degrees make sure it is big enough to fit over the mummy
without compressing it). Keep in mind that each of these options has
advantages and disadvantages in terms of price, weight, and volume
taken up in your pack.
You also need to insulate yourself from the underlying snow. Foam
pads (Ensolite) or inflatables (Thermarest) work well. Your
insulation should be a least 1/2 " thick (two 3/8 " summer pads work
well, or use a Thermarest on top of a 3/8 " foam pad). It best to
use full length pads so that all of your body is insulated.
Stoves versus. Fires
In most cases you will be taking stoves and fuel for cooking.
Fires are possible in some locations, but in high use areas, it is
best to rely on a stove as firewood can be difficult to find in the
winter. Your stove should have good heat output. In order to
insulate the stove from the snow (so it doesn't melt itself into a
hole) place something underneath it like a pot lid, or a piece of
fiberboard. Since the burner is usually significantly smaller than
the pot bottom, placing a metal pot lid on top of the burner can
also help spread the heat more efficiently to the pot. Wind shields
are also helpful in the winter to concentrate the heat. Priming
stoves in the winter can be difficult. It is best to use alcohol or
lighter fluid rather than trying to prime the stove with white gas.
Fuel - plan on 1/4 quart per person per day if you need to
melt snow for water. Plan on 1/8 quart per person per day if water
will be available. Make sure you have at least a day's surplus of
fuel in case of bad weather, water being unavailable, etc.
Planning food for winter activities must take into account the
great demands the cold weather and physical activity placed on the
body along with the difficulty of preparing foods in the winter (it
takes time, stove fuel) and having a menu which appeals to the
group). Appetite is generally reduced during winter activity even
through the food needs of the body have increased. If the meal isn't
appealing, it won't get eaten. In some situations you literally need
to force yourself to eat.
All foods are made up of varying proportions of the three basic
food types - carbohydrates, fats, proteins, and water, vitamins and
minerals. Each of the three major types can be converted into simple
sugars and burned by the body to produce energy but the time
required for conversion increases as the complexity of the molecule
increases, so carbohydrates are quicker to convert than proteins and
proteins quicker than fats.
|Dietary Percentage for Winter
||5 calories/gram (1,800
cal./lb.) - released quickly.|
||5 calories/gram (1,800
cal/lb.) - released quickly. They are easy to digest. Candy,
cereal, bread, rice, macaroni, dried fruit, vegetables.|
||5 calories/gram (1,800
cal/lb.) - generally released slowly. Proteins are primarily
used for maintenance and building of body tissue. Meat, fish,
cheese, milk, eggs, nuts, grains.|
||9 calories/gram (4,100
cal/lb.) - released very slowly but are useful because they
release heat over a long period. However, it takes more energy
and more water to break down fats into glucose. Margarine,
nuts, cheese, eggs, and fats from pepperoni,
Vitamins and Minerals - are generally found in most foods
we eat and for a trip less than 7-10 days no special resources are
needed. For longer trips and expeditions vitamin and mineral
supplements are necessary. See a physician to get specific
recommendations for expeditions.
General caloric requirements increase in the winter due to the
energy expended in keeping the body warm. Caloric requirements for
different activity levels are summarized below.
Keep in mind that there are definite individual variances on
these figures based on age, body metabolism, health, etc.
Avoid taking fresh food in the winter (fresh fruit, vegetables,
eggs). These all contain water and weigh a lot (and you have enough
to carry). The exception to this is cheese, butter, or meats (needed
for their high fat content). Take mostly dry foods (cereal, pasta,
rice, wheat, oatmeal,) baked goods (brownies, cookies), or freeze
dried foods (expensive but very lightweight and quick to cook which
can save on stove fuel).
1. Breakfast - should not be a complicated meal but should
be a complete one since it supplies the foundation for a full day's
work. Time is also a factor since you probably want to get up and
moving. Just standing around in camp in the early morning (cold)
hours only leads to cold feet and bodies. Since the easiest thing to
cook is water it is best to go for items which can be made in each
individual's cup. Suggestions include: instant oatmeal with hot milk
& margarine, hot Tang, Granola with hot milk, hot Jello, hot
chocolate with extra milk & margarine.
It is best to supplement some of these items with extra powdered
milk to add additional protein and margarine for fats. This is the
meal to be careful not to dump too much sugar into the
bloodstream at once, but rather to eat a good mix of all three major
food types. The sugars will get you started and the proteins and
fats will keep you going through the morning.
2. Lunch - There are two approaches to lunch on a winter
trip. One is to stop for a traditional lunch and take a long break.
This means cessation of activity which can lead to people getting
cold. Additional layers would need to be put on and taken off. All
of this adds up to a lot of time. But this also allows time for
exploring an area and taking it easy. You can break out the stove
and cook up a hot meal if you like. The other approach is carrying a
personal lunch which can be eaten throughout the day, at scenic
points, water stops, clothing breaks, etc. The second approach
minimizes the amount of time people would be standing around, but
also doesn't provide a major rest stop. In both cases you should
include all the food groups by having some of the following items:
meats, cheeses, nuts, dried fruit, raisins, cookies, candy, granola
In the case of an "eat through the day lunch" a general formula
is to take the following per person per day:
- 1/2 - 3/4 lb. GORP - raisins, peanuts, M&M's, sourballs
coconut, chocolate morsels etc.
- 1/4 - 1/2 lb. Lunch Meat and/or Cheese - cut into bite size
chunks so you don't break your teeth
- Other items include cookies, brownies, peanut butter, bagels,
3. Dinner - It is often good to start dinner with an
instant soup or a hot drink that can be made in each persons' cup.
This gives some internal warmth while waiting for the main course.
In the winter, the main dish is usually some form of one pot
glop/stew. This is to save time and stove fuel. A glop starts with a
soup or gravy base, and includes a starch (rice, noodles), some
vegetables (frozen vegetables keep well on winter trips), whatever
protein you are carrying (lunch meat, cheese, canned chicken, tuna).
This should be spiced to make it tasty. Remember, at the end of the
day you will be more tired than hungry and having an interesting
meal is essential to get you to eat.
The other approach to dinner is freeze-dried foods. These have
the advantage of simply adding the dish to boiling water so less
fuel is needed and they weigh very little. There are a number of
companies offering these items. They are generally more expensive
than what you would pay for basic staples like rice & noodles.
Be aware of portion size. Some companies give an unrealistically
high estimate on how many their meal pack will feed.
The meal is concluded with hot drinks (tang, tea, hot chocolate,
jello etc.) and possibly dessert. At the end of the meal water
should be melted/heated up for personal water bottles at night.
(See water section below).
Dehydrated foods (which are different than freeze dried are
not recommended because they require large quantities of water
to rehydrate them.
4. Food for sleeping - you need to take some of your lunch
for the next day to bed with you. This allows fresh items like the
meat and cheese to thaw. If you wake in the middle of the night and
are cold (or just before you go off to sleep) it is best to eat
proteins. The protein will be broken down more slowly so the heat
will be released over a longer period of time. If you eat a sugar,
you will get a quick "heat high" and then your body temperature will
drop back down, sometimes falling below its previous level.
5. Utensils - all the personal utensils you will need is a
large plastic cup (insulated if possible) and a plastic spoon.
(Do not bring metal utensils in winter). It is also
recommended that you tie an idiot string between the cup and the
spoon. Cleaning these utensils is generally only scraping out the
remainder with snow. Anything left will be part of your next meal.
6. Food Packing - You will need to repack you food to
minimize the amount of trash you bring in with you. It is best to
combine food items by meal or type into separate stuff sacks
(breakfast bag, lunch bag, dinner bag, hot drink & dessert bag).
Label them or color code them so you can easily distinguish them.
1) Do not eat snow! It takes an incredible amount
of energy to transfer water from one state to another (solid to
liquid). You are burning up too many calories to do this which can
quickly lead to hypothermia.
2) Water may be obtained by digging a hole in frozen lakes or
streams where there is running water beneath the ice. Be careful
about falling in. Remember, in most cases water will need to be
purified from giardia and other bacteriological contaminants (see
3) Snow can be melted on a fire or stove to make water. It should
be clean snow, no yellow (urine) or pink (bacterial
growth). Because it takes so much energy to convert from one state
to another you should have some water in the bottom of your
container. Heat this water up and add snow to it slowly so it turns
to slush and then water. This is much more efficient. If you dump in
straight snow, you will only burn the bottom of your container and
not make any water. By volume it takes about 10 quarts of snow to
make 1 quart of water. Snow does not need purification.
4) Winter Solar Water Collector - In a spot that will remain
sunny for several hours, dig out a depression in the snow about 2
feet across and 1 foot deep. If possible, line this depression with
a foam pad or other insulation (not essential but it speeds the
process). Then spread a dark plastic bag (trashbag) over the
depression forming a shallow dish pan. All over the raised margins
pack clean snow. Drawn by the dark plastic the sun's
energy will melt the snow and water will collect in the
5) Water in a pot can be stored overnight by placing the pot lid
on and burying the pot under a foot of snow. Snow is such a good
insulator that it will keep the water from completely freezing even
in sub-zero temperatures.
6) Personal Water - You should have a water bottle with a wide
mouth, otherwise the opening will easily freeze up. During the day
you should carry at least one bottle next to your body (usually with
a shoulder strap arrangement). Your body heat will keep it from
freezing and the bottle is handy to rehydrate yourself throughout
the day. Insulated water bottle holders are available for this.
Other bottles can be kept upside down in an insulated container
(sock etc.) preferably in an outside pocket on your pack. Being
upside down will keep the mouth of the bottle from freezing. Keep
in mind that the lid must be on tightly or water will leak all over
the place. A cold water bottle may have ice crystals in the
threads. As the bottle heats up from body temperature the ice may
melt causing the cap to loosen also the lid may expand with heat
causing leakage. At night keep your water bottles in your sleeping
bag to prevent them from freezing.
7) Getting Water - sometimes filling pots and water bottles from
a stream or lake is a major expedition in itself. Make sure that the
area you plan to get water from is secure. Avoid steep banks that
might lead to a plunge and make sure any ice is sufficiently stable
to hold your weight. Also make sure you don't get your mittens
soaked with icy water. A loop of string tied tightly around the
water bottle neck will allow you to lower a bottle in by hand or
with a ski pole or ice axe. Don't trust pot grips on a large pot,
with mittens you can lose your grip and your pot. Fill the pot up
part way and then use a water bottle to top it off. Mark the area so
you can find it next time.
8) Water purification - keep in mind that water gotten from
streams in the winter time may have bacteriological or other
contaminants. You should check with local rangers about any water
problems before going in. If the water does need to be purified, the
best methods during the winter are either:
- Boiling - for at least 3-5 minutes (add 1 minute for
every 1,000 feet above sea level so that at 10,000 feet you are
boiling for 15 minutes). This is the best method in winter
- Less Effective Methods:
- Filtration- using a filtration pump system such as
the PUR, First Need, or the Katadyn is not recommended in
subfreezing temperatures. Keep in mind that the water in filters
can freeze preventing them from working. Also, as the water
freezes, it expands and may crack the filter, rendering it
inoperable or even worse transmitting harmful microorganisms
into your system. For these reasons, filters should be used with
great caution in the winter. Be careful of inferior filters
which do not strain out many organisms.
- Chemical treatments (iodination or chlorination) are
not recommended because they become ineffective at
low temperatures. Only use these methods if the water has been
preheated to about 60o Fahrenheit.
In many cases you will be traveling to areas without shelters, so
you need to bring your own. There are a range of tents available.
The key factors are:
- Strength - to withstand both wind and snow. In general it is
recommended that you use a tent specifically rated to be a
4-season tent. Four season tents typically have stronger poles (to
hold snow loads).
- Ability to shed snow - the tent must have a roof line that
allows snow to fall off. Otherwise the tent will load up and the
weight will cause it to collapse. (Four season tents are designed
- Room - you need lots of internal space on a winter trip
for all the bulky gear you are carrying. Also you may get snowed
in and need to stay in the tent for an extended period of time.
Being snowbound in a cramped tent with several other people can be
- Rainfly - the tent must have a rainfly. Having a breathable
inner tent wall with a waterproof fly outside helps reduce
condensation in the tent (see below). It also helps provide better
insulation by increasing (relatively) unmoving air space layers.
Typically a tent will be 10-20 degrees warmer than the outside air
(once your body is inside heating it up).
- Free standing tents (dome type) are recommended because they
shed snow fairly well and they provide efficient interior space.
Make sure that the manufacturer recommends the tent for
winter use. Many dome tents are designed for three season use only
and the stitching and the poles are not designed to take the
weight of snow.
- Other shelter options include the Black Diamond Megamid. This
a single, center pole, pyramid tent with no floor. They require
some staking but are quit roomy. By adding a space blanket as a
floor, and covering the edges with snow, you can seal off the tent
- Another issue with tents is condensation. During the night
your breathing pumps a great deal of humid air into the tent. This
air rises and hits the inner tent wall where the moisture
condenses into ice. These fine particles can get all over you and
your gear. It is best to brush the ice particles off the tent in
the morning and sweep them outside. A frost liner, hung inside the
tent, allows the moisture to pass through and provides a layer
between you and the ice.
Tips for Tents
- Make sure you bring extra poles with you and pole splints in
case a pole breaks.
- A ground sheet (like a space blanket or tarp) can help protect
your tent floor (the ground underneath usually turns to ice from
your weight and body heat. Sharp ice can tear the floor)
- Always stake you tent down if you are going to be in windy
areas or leaving your tents during day excursions. Bring stakes or
know how to stake using "dead men."
- Wisk Broom - is an important addition to every tent.
You should brush all the snow off your clothes and boots before
getting into the tent at night. This helps reduce condensation and
water buildup in the tent keeping you and your belongings dryer.
Also when snow gets into the tent at night it often melts from
your body temperature, then freezes during the day when you are
not in the tent.
- Cooking - Do not cook in a tent. It is possible to
asphyxiate yourself from accumulated carbon monoxide and the water
vapor leads to extensive condensation.
Keep the following factors in mind when choosing a winter camp.
- Camping regulations
- Other campers
- Wind - avoid ridge tops and open areas where wind can blow
down tents or create drifts.
- Be aware of "widow makers", dead branches hanging in trees.
- Avoid low lying areas where the coldest air will settle.
- Avalanche danger - select sites that do not pose any risk from
- Exposure - south facing areas will give longer days and more
- Water availability from lakes or streams will prevent you
having to melt snow for all your water.
- Level ground
Setting up Camp
When you first get into camp, leave your snowshoes or skis on and
begin to tramp down areas for tents and your kitchen. If possible,
let the snow set up for 30 minutes or so, this will minimize
postholing once you take snowshoes or skis off. Set up your tents
with the doors at 90 degrees to the prevailing winds. Stake the
tents out. On a cold night you can build snow walls on the windward
side of the tent. Mound the sides of the tent with snow (have
someone inside pushing out on the tent to keep it from collapsing.
When the snow sets up you will have a hybrid tent-snow shelter which
will have better insulation than the tent alone. Dig out a pit in
front of your tent for a porch. This makes taking your boots off
much easier. Put your foam pads in the tent and unstuff your
sleeping bag and place it in the tent so it can "expand" from it's
If the snow is deep, you may want to dig out a pit for your
kitchen. Dig a pit at least 6 feet in diameter (for 4-6 people). You
can mark out the circle using a ski or a rope. Dig down about 2-3
feet and pile the excavated snow around the perimeter. Pack the snow
at the perimeter of the hole with your shovel. This will give you a
4-5 foot deep area, protected from the wind. You can carve out seats
and benches, put your skis or snow shoes behind the pile as
backrests, carve places for stoves, etc.
General night sequence - after dinner, getting warm water
for water bottles, and putting gear away, it's time for bed. This is
a general sequence:
- Get warm before you get into your bag. Do some jumping jacks,
etc. so your heat is built up for when you get in your bag.
- Get any clothing/gear you will need out of your pack as well
as full water bottles and tomorrow's lunch.
- At the tent door, brush off any snow with the wisk broom. Sit
down inside the tent entrance and, keeping your boots outside,
either have a friend brush them off, or remove them and brush them
- Climb into the tent and close the door.
- Strip off your layers of clothing to what will be appropriate
in your sleeping bag. The more layers you wear the better
insulated and the warmer you will be (contrary to the myth that
says sleep in your underwear). However, too much clothing can
compress dead air space in the bag and reduce its effectiveness.
- Remove any wet/damp layers and replace them with dry ones,
- Pre-warm your bag with your body (get it nice and toasty).
- Place damp items in the sleeping bag with you near your trunk.
This will help dry them overnight.
- Place your boots in your sleeping bag stuff sack (turned
inside out) and place the stuff sack between your legs. This will
keep them from freezing during the night and the stuff sack keeps
your legs from getting wet.
- Put water bottles and food with you in the bag.
- A hat and polarguard booties are recommended to help keep you
- Try to sleep with your face out of the bag. This reduces
moisture build-up inside the bag (which could be catastrophic for
a down bag). A scarf on your neck may be better than using the
sleeping bag neck drawcord (which makes some people feel a little
claustrophobic and creates a difficult nights sleep).
- You will probably wake up a number of times during the night.
This is normal in cold weather. Your body needs to change position
to allow for circulation to compressed tissues and to move around
a bit so that muscle movement generates more heat. If you are
still cold, eat some protein to "stoke up your furnace" If that
doesn't work, wake a tent-mate for some extra warmth.
- With 10 or more hours in the tent, you are likely to need to
urinate in the middle of the night. Go for it! Otherwise you won't
get back to sleep, and your body is wasting energy keep all that
extra fluid warm. You will be surprised how quickly you can get
out and back in and your body really won't chill that much.
- It is useful to have a thermos of hot drink in each tent.
The following snow shelters are also useful in winter. Keep in
mind that there is great potential for getting your clothing wet
while constructing these shelters. You should be dressed
Snow Mound Shelter (Quin-zhee) - If the party does not
have the experience or the snow conditions aren't good for an igloo,
a snow mound shelter can be made. In a selected spot, place an
upright marker (ski pole, ice axe, etc.) to mark the center. Tie a
cord to the marker and scribe a circle in the snow to indicate the
pile size. The rule of thumb for size: if the snow in place is not
to be dug out, the radius should be the interior size plus about 2
feet; if the snow in place is to be dug out, about 1 foot can be
subtracted from the radius for each foot of in-place snow. Piling
the snow for a two person shelter will take two people about an
hour. Pile loose snow within the marked circle with shovels, tarp
etc. Don't compact the snow. When the mound is the right size and
shape, do not disturb it; allow it to compact naturally - minimum
time one hour. Chances of collapse are greatly reduced if you let it
settle for two hours. Thirty-five degrees is the natural angle at
which loose snow rests. Be sure to allow the snow to settle at this
angle. Otherwise you will have thin spots or a buckling roof when
you excavate the interior. After compaction you are ready for
digging. The entrance direction should be away from the prevailing
incoming weather. From the entrance point start digging toward the
marker. Pass the snow out to helpers. As soon as you reach the
marker, do no not disturb it. This is your guide for excavating the
interior. Clear out the inside to the intended radius. To check on
wall and roof thickness, measure with a stick poked through. When
the dimensions check, remove the marker and trim the interior. Then
install a vent in the roof. Get rid of waste snow promptly before it
hardens. The process is a wet one so make sure you have waterproof
gear on and good shovels for making the mound and digging out.
Snow Cave - A snow cave can be dug into a hillside. Dig
the entrance up so that the door is below the sitting level. Also
there are natural snow caves formed by the overhanging branches of
trees covered with snow. By digging down you can get into the cave
beneath the branches. In both cases you should poke a ventilation
hole and keep it clear.
Igloo - can be constructed if there is snow of the proper
consistency to pack into hard blocks. Keep in mind that building
such a shelter takes a great deal of energy and time. Two skilled
persons can build a two person igloo in 2-3 hours with proper
equipment and good snow. Obviously several such structures would
need to be built to hold a larger group. Building an igloo is a
process that requires a certain amount of artistry, but is less of
an energy expenditure than a snow mound shelter. In general,
rectangular blocks roughly 24" by 18" by 6" are cut and stacked in
an ascending spiral. The rectangular blocks are placed vertically
and the bottom shaped so that only the two bottom corners are
supporting the block. Then the block is tilted inward and the
vertical edge contacting the adjacent block is cut away until the
weight of the block rests only on the upper corner. The weight of
the block is supported by the diagonally opposite corners, while the
third corner prevents rotation. Once the first row is laid you shave
off the tops of several blocks ( 1/4 - 1/3 of the circumference) to
create a ramp and build upward in a spiral. Once the structure is
complete, snow is packed into all the open joints. (See the Off
Belay reprint Igloo.)
Snow Pit - This structure can be created by digging a
trench in the snow down to ground level (if possible). The structure
should be a little longer than your body and 3 - 4 feet wide. Line
the bottom with insulative material to insulate you from the cold
ground (in an emergency you can use 5-6 inches of evergreen boughs).
A roof can be made of skis and poles or overlapping boughs and
sticks then covered with a tarp and then loose snow or blocks of
hard pack snow. The doorway will be a tunnel in from the side. This
can be plugged with a door of hard pack snow. A ventilation
hole must be poked into the roof for air flow. Keeping a
stick in this hole and shaking it every so often will keep the hole
open. If possible, the entrance should be lower than the level of
the trench, this keeps the coldest air in the entrance rather than
in the trench.
Winter generally provides a blanket of snow which protects
underlying soil and vegetation, the major concerns for minimizing
impact. However, when thin snow cover is compressed and compacted in
early or late season, snowmelt can be delayed, shortening the
growing season. Also, early and late winter trips can run into
melting conditions, where top layers of soil melted by the sun lie
overtop frozen ground. Erosion, and destruction of plant life is
extremely likely at these times, and winter travel is best avoided.
Otherwise travel in small groups and visit either remote places
where your disturbances won't be compounded by others following you
(allowing for recovery) or high impact areas that have already been
disturbed. Special considerations exist for high altitude and
glacier conditions (see Soft Paths).
Backcountry travel and camping
- Winter clothing and equipment, even when "natural" colored
will show up well against the snow. Brighter colors can be a
safety measure, as people and equipment can easily be lost in a
winter storm. Since there are less people out in the winter, the
visual impact is less.
- Winter is an exceptionally quiet season in the backcountry.
Travel quietly and avoid excess commotion at your campsite.
- One of the greatest impacts can be on wildlife. Animals in the
winter have limited food supplies and are often stressed to their
limits to survive. Being disturbed by backcountry travelers can
drive them away from food sources, require them to use more
energy, and can lead to death. Animals may seem more
"approachable" in the winter. This is because they are trying to
conserve energy. Do not approach wildlife too closely.
- Tent, igloo and snow cave sites should be selected away from
trails and open bodies of water if possible.
- All campsites and cooking areas should be disguised when you
leave so that accidental stains are covered, and so that camping
areas will be undetectable after 2 - 3 inches of snow has fallen.
- Large snow structures such as igloos and snow caves can be
left intact, as long as the rest of the camping area is well
camouflaged. Occasionally these snow structures can be used again
by other grateful winter travelers.
- Camp away from animal feeding, watering, and bedding areas.
- Fires - Under winter conditions, it can be difficult to
build a disguisable fireplace or to gather wood by acceptable
means. Since any downed wood is under the snow and possibly wet,
wood is both difficult to find and may not be usable for a fire.
Gathering wood from lives trees can have significant impacts on an
area especially at high use sites. Therefore, one should carefully
examine the location, the ecosystem, and the ability to clean up
the site after the fire before deciding to build one. Obviously,
in a real emergency, a fire might need to be built in spite of the
impact it might have on the environment
- Sanitation - Lack of sunlight and cold temperatures
retard the decomposition of fecal material.
- Maximizing sunlight will help but will leave a visual impact
if others are in the area. The best solution is to dig a cathole
in just below the surface of the snow. Keep in mind that after the
thaw, the feces will be resting on the ground. So pick a cathole
site far from any water, summer trails, or summer camping areas.
Locate a site with as much ground cover (grass or forest
downfall), and as little slope as possible to minimize washing
into surface water, and maximize feces-soil contact.
- For maximum fecal dispersion, persons should make personal
holes as needed. There is no reason for a group's waste to be
deposited in one place. Head away from camp. Snow should be kicked
over urine stains to prevent the "yellow snow" effect. Toilet
paper can be a problem in the winter. Burning it once it has hit
the snow is very difficult. You can burn it in a tin can or pack
it out. A better idea may be to use snow or ice (although powder
snow is difficult to use).
- You almost never need to wash pans in the winter. A simple
scouring with snow will freeze all particles. They can be packed
out with garbage (or left for the next meal). Ending dinner with
hot drinks usually takes care of any food particles. Water left
over from pasta is full of carbohydrates and makes good drink
water. If you do have leftover cooking water, solid food waste
should be strained out of the water and packed out. The water
should be concentrated in sump holes far from water sources to
prevent massive unsightly stains on the snow. The sump holes
should be covered when breaking camp. Leftover grease will cool to
a solid and can be carried out. Minimize all solid food since
animals will often dig up sump holes.
- Litter is especially difficult to check in the winter when
dropped items can be lost so easily in the snow. Special attention
should be given to plastic bags, white toilet paper (use colored
or better unbleached, or use snow or ice), candy wrappers and
candle wax. Candy wrappers should be removed from all candy before
leaving town to prevent accidental litter. Candle wax should be
caught in a cup and packed out.
Travel in the winter depends a lot on what form of locomotion
(feet, snowshoes, skis). There are some general travel techniques
that are applicable to all forms of winter travel.
- When breaking trail, rotate the leader. Have the leader step
off the trail and the rest of the group passes. This person drops
into the last position (like a goose) for a rest while the second
in line takes over. You can also have a lighter pack that is
carried by the person in front and switched off.
- Map and compass is often critical in winter travel since you
may be off trail or trails may be hidden by the snow. Feel for
difference in the snow between a packed trail and unpacked. Look
for opening line above in the trees which could indicate the trail
- When bushwacking, wear goggles to protect your eyes.
- When bushwacking or traveling through dense brush and forest,
take your hands out of your ski pole straps. If the basket catches
on something and you fall, being in the straps can lead to a
- Watch out for "spruce traps," evergreens with the lower
branches covered with snow. Beneath there is an air pocket ready
to swallow you up (this can be used for an emergency shelter - see
- Whiteouts can be extremely dangerous. Even skilled
mountaineers have become disoriented and walked off cliffs. Decide
1) if it is safe to continue 2) if it is really necessary for you
to continue. Otherwise, set up camp where you are if possible, or
hunker down (in a group) with lots of layers on and wait until
conditions improve. If you decide to continue, know where you are
going and what possible dangers lie ahead. Stay close together and
in constant voice contact with the people in front of you and
behind you. If one person has to stop, the whole group has to
stop. If you are following cairns, have the group stop at the last
cairn, send one person out tied into a rope (with a compass and on
the right bearing) to find the next cairn. People can then follow
Coming up to a frozen or snow covered lake in the middle of
winter raises sudden safety questions for winter travelers whether
you are on foot, snowshoes, or skis. Will the ice hold? What happens
if I break through? Here is a collection of information to help with
both of these questions.
Ice Formation (temperatures based on fresh
As surface water on a stream or lake is chilled by the low
atmospheric temperature, the water contracts and sinks to the bottom
where it is chilled to the point of the greatest density of water,
where molecules are packed as closely as it is possible for them to
be. This critical temperature is 39o Fahrenheit (4oC). The dense,
cold water sinking to the bottom displaces water at a higher
temperature which rises to the top. Thus vertical convection
currents are produced. This process continues until the entire body
of water reaches 39o Fahrenheit. Then the water can no longer sink.
Instead it is progressively cooled at the surface. As the water
chills below 39o Fahrenheit it starts to expand, until at 32o
Fahrenheit (0o C) it changes state and becomes a solid by expanding
into a lattice structure that is lighter than the liquid state. From
the description of this process, it is clear that flowing water will
require a greater length of time to freeze than still water and that
shallower depths near the shore of any body of water will reach a
uniform 39o Fahrenheit sooner. Thus, ice on a small pond that can
support a person's weight cannot be used to gauge the safety of ice
midstream or in the middle of a lake.
Generally the first type of ice to form on a lake is called
black ice. This is a misnomer because the ice itself is
clearit is the water seen through the ice that looks black. If a
prolonged spell of clear, cold weather occurs after the lake first
freezes, this black ice initially grows quite rapidly. However, as
is thickens it insulates the water underneath from the atmospheric
temperature, and ice growth slows.
As snow accumulates on the lake, the stage is set for a major
change in the characteristic of lake ice. The snow cover, when it's
deep enough, begins to exert downward pressure on the black ice, and
pushes it beneath the hydrostatic water level of the lake. If a
period of cold weather follows, thermal contraction of the black ice
produces cracks, which allow the lake water to rise up and flood the
surface. This is called a slushing event.
Since the lake is under pressure it spills out, and as it
freezes, turns the snow cover to ice. The new ice layer contains
many air bubbles between the snow crystals and therefore appears
white. This white ice forms on top of black ice, and with
further snowfalls and cold periods, the process may be repeated
throughout the winter. When struck white ice gives a solid sounding
Because of the close link between snow accumulation and white ice
production, it's not surprising to find a predictable pattern of ice
types on a lake. Snow in the center of a lake may be redistributed
onto the downwind sides of the lake and along the shoreline. Thus,
it's not surprising to discover that these area also have the
greatest thickness of white ice. A lake's snow cover is frequently
much thinner than the surrounding shore's due to removal by wind and
conversion of snow to white ice during slushing events, and may be a
preferred route for snowshoers or skiers.
The following are guidelines which will help you determine which
routes to follow across a frozen body of water.
- Lakes - watch for constrictions where rivers or streams enter
or exit. These are likely to be thin.
- Rivers - care should be taken when crossing on the outside of
bends or at the center of the river in straight sections. Also
sections of rapids, where tributaries join, or where the river is
constricted should be avoided. All of these areas have the
greatest current flow which means less stable ice.
- Since thinning of ice by under-ice water currents is often
difficult to ascertain especially when it's snow-covered, test the
ice periodically by using your ski poles to tap out the ice in
front of you. Vibrations will tell you about the ice thickness,
structure and strength. If the ice is suspect, move around the
area or move back to a safe location and chip a small hole to
check the thickness and type of ice.
- Spring-fed bodies of water may have flow percolating up in
different sites causing less stable ice.
- The continuity of ice and hence its structural strength is
greatly diminished when freezing occurs in swamps with alder or
- Logs, stumps, rocks, earth hummocks, basically anything
sticking up out of the ice picks up heat from the sun during the
day; some of this heat melts the ice surrounding the object. These
obstructions often have weak "moats" of ice surrounding them and
are prone to breakthroughs.
- Ice formed during a snowstorm amounts to frozen slush that
will appear grey to white and have a pebbly, opaque surface, the
result of microscopic trapped air bubbles that resist cohesion,
weakening tensile strength by as much as half.
- Water on top of ice is dangerous, especially during warm
spells and in the spring. Water is heavier than ice, and as a
result it leaks down through it, creating fractures known as
honeycombs. No matter how thick it may be, honeycombed ice
can give way.
- Beware of dark patches in ice. They may be a sign that the
water underneath has melted and thinned the ice from below, a
common situation around underground springs and current lanes.
Moving water of any kind eats away at the ice above it.
- The surrounding landforms or lake geography also suggest some
things about ice. The deeper the lake and the longer it takes to
freeze tight, the harder and safer the ice will be. In the winter
(in the northern hemisphere) the sun is to the south, so areas
that face north get less sun exposure. This means that ice will be
thickest along the south shore (north-facing) of a lake and
thinnest along the north shore (south-facing).
- Straight open cracks may be safe to cross even if there is
open water. If two or more cracks meet at open water, crossing is
- Discolored snow over ice may indicate water or a slushing
event. If the snow looks dark or slushy, avoid the area.
- A depression of slump in a normally even snow surface may
indicate soft ice underneath.
- Ice jams with smashed blocks of ice piled on one another are
often found downstream of rapids. This means the area upstream may
not be safe to cross because of fast moving water.
- Overflow caused by water seeping up through cracks in the ice
or over the edges near banks can saturate the snow cover and
create deep wet slush. A new layer of ice can form on top. If this
layer is covered with snow it may be indistinguishable from the
snow surface (although a pole tap will give a very different
- Remember that ice will support your weight best if you're on
snowshoes or skis (greater surface for weight distribution), so
don't stop to remove skis or snowshoes in the middle of a lake or
river, especially if you think the ice could be thin. If your skis
are icing up, wait until you reach land before scraping and
rewaxing. It's not only safer, but you'll avoid getting your boots
Ice Safety and Rescue
- Keep in mind that, like avalanches, ice can give way on the
first person or the last or not at all. You can cross any area
safely during the morning and then have it give way on your way
back in the afternoon. Therefore, you always need to be
- Spread the group out so as not to concentrate weight on the
- The lead person should be probing ahead with a ski pole or
similar object. Poke the ice fairly hard. If the probe goes
through, turn back and find another route. You can also hear a
different sound with solid ice (sound - tick) versus thin ice over
an air pocket (sound - tock).
- Avoid the danger areas outlined above, why not try a trail
around the lake if you are not sure about the ice?
- If you have serious concerns about the ice, make sure your
pack hipbelt and chest compression strap are off. This will allow
you to quickly jettison your pack if you fall through. If you go
through, immediately shed your pack and kick to the surface.
- Self-rescue - Attempt self-rescue by extending your
arms forward over the ice , kicking the legs up so that the body
is in a level position in the water, and working forward onto the
ice by kicking and carefully pulling with the arms. A pocketknife
or other sharp object can be used in the hand to increase
traction. This maneuver can be successful even if the ice
continues to break ahead of the victim; it should be continued
until firm ice is reached. After pulling the entire body onto firm
ice, the victim should carefully roll or edge toward shore,
distributing body weight as widely as possible.
- Group rescue
- Check on everyone and make sure the rest of the group is one
safe ice. If not have people crawl (not walk) to safety
(crawling spreads on the weight).
- Toss a throw rope to the person to stabilize them (an
essential piece of equipment). This will also help minimize
panic and give you something to help pull them out.
- Stay a safe distance from the hole. If necessary, lie down
on the ice and extend objects towards the hole (skis, ski poles,
etc.). If necessary, a human chain can be formed by laying down
on the ice and grabbing the ankles of the person in front of
you. The person closest to shore is "on belay" for the group.
Don't try to reach the person with your body, in their
panic and struggle (like a drowning person) there is a good
chance they will pull you in.
- Span the edge of the hole with skis or saplings extended to
the person. Since the ice is likely to keep breaking as they try
to climb out, this gives them something to climb onto and
distributes the weight. Use the rope to help pull the person
out. They will need to kick their feet to the surface to be as
horizontal as possible.
- Once the person is out of the water. Begin immediate
assessment and treatment for hypothermia. Rolling them
in the sow can blot up some of the water in their clothing.
As a general guideline, 1 inch of black or white ice will
probably hold you up. Two inches is safe, and six inches will hold
up a moose. Thickness of suspect ice can usually be determined quite
quickly by using an ice axe or auger to drill through. However, for
advanced trip planning, you can use the following formula to
estimate the thickness:
Z = ice thickness in inches
S = degree days accumulated below 32 oF
A = a coefficient which varies as follows:
(.8) - windy lake with no snow
(.5 to .7) - average lake with snow cover
(.5 to .7) - average river with snow cover
(.2 to .4) - sheltered small river with rapid flow
S is calculated as follows: Suppose ice is formed December 15 and
the mean temperature for December 16 was 5o F. To find degree days,
subtract 5o F from 32o F for a value of 27. If on December 17 the
temperature is 4o F, subtract 4o F from 32o F for a value of 28. S
would then have a value of 55 by December 17
(27o F + 28o F =
55). Next take the square root of 55 (7.4). To determine ice
thickness, multiple 7.4 by the appropriate coefficient A (say .8 for
a windy lake with no snow), and your answer is 5.9 inches of ice.
If you don't know the date of ice formation, you can estimate by
the following technique:
- For lakes 3 - 10 feet deep, freezing occurs very close to the
date when the 3-day running mean temperature is 32o F and where
temperatures remained mostly below that for the rest of the
- For lakes 20 - 50 feet deep, the date of freeze-over occurs
when the 40-day running mean temperature reaches 32o F.
- AMC Guide to Winter Camping, Stephen Gorman, AMC Books,
- Winterwise: A Backpacker's Guide, John Dunn, Adirondack
Mountain Club, 1988.
- Winter Hiking and Camping, John Danielson, Adirondack
Mountain Club, 1982.
- Outdoor Emergency Care, Warren D. Bowman, National Ski
Patrol System, 1988.
- Soft Paths, Bruce Hampton and David Cole, NOLS, 1988.
- Snow Caves for Fun and Survival, Ernest Wilkinson,
Johnson Books, Boulder, 1992.
- Insulation - the Thick and Thin of It, Backpacker
- Food for Winter Mountaineering, Appalachian Mountain
Club Winter School
- Clothing for Winter Mountaineering, Appalachian
Mountain Club Winter School
- Patagonia Products Literature
- Igloo, Off Belay Magazine Reprint, 1975
- Getting Winter Water, Backpacker Magazine, January,
- NOLS Minimal Impact Camping Practices
- The information on ice crossings is taken directly from the
following two articles.
- How Thick Should the Ice Be?, Douglas Ayres Jr.,
Adirondac Magazine, January, 1987.
- How Safe Is That Ice?, Keith Nicol, Backpacker
Magazine, January, 1983. Graphics are adaptations of the
accompanying illustrations by Peter Thorpe.
- Winter: An Ecological Handbook, James Halfpenny and Roy
Douglas Ozanne, Johnson Books, Boulder, 1989.
- A Guide to Nature in Winter, Donald W. Stokes, Little
Brown, Boston, 1976.
|Avalanches can be
extremely hazardous. This information is only a brief overview
of an extremely complicated subject. Know your terrain
before you go. Is avalanche a possibility? If so, check with
local avalanche forecasts. When traveling in avalanche-prone
areas you must be knowledgeable in terrain recognition, route
planning, avalanche area avoidance, and avalanche search and
rescue techniques. Always carry the proper gear like shovels,
avalanche transceivers, and probe poles. If you don't know
what these things are, you don't have any business traveling
in avalanche-prone terrain.|
Loose Snow Avalanches - These start from a single
point incorporating more and more unconsolidated snow as they fan
out. They are caused when the weight of new fallen snow succumbs to
the forces of gravity. This occurs most often after periods of heavy
snow (10-12 inches accumulation, or snowfall or 1 inch or more per
hour) especially when piled on top of a smooth snow surface (from
thawing, freezing, or rain) The smooth snow surface provides a slick
ramp for the heavy new snow to run down.
Slab Avalanches - Are caused when well compacted
and cohesive layers of snow aren't anchored to the slope. If there
is a weak layer of snow underneath the compacted layer, the slope is
primed to avalanche. Various forces, sun, wind, or a person can
trigger the slab at the release zone.
Avalanche Sites - Open slopes between 25 and 45
degrees. Especially lee slopes (the direction toward which the wind
is blowing) which get greater snow loads.
- Most victims trigger their own avalanche.
- Be aware of your surroundings. Watch for evidence of sliding,
snow sluffs - small slides indicating avalanche danger, avalanche
chutes or slides where trees have been torn away, or snow debris
at the bottom of a slope indicating previous avalanches.
- Keep track of the weather. The first 24 hours after a heavy
snow, high wind, rain, or thaw is the most dangerous period. Check
local avalanche forecasts and be prepared to postpone your trip if
the danger is high. Delaying for 24-48 hours can significantly
reduce the danger.
- Recognize danger zones and be conservative about planning your
route or crossing a slope.
- Travel on ridge tops or heavily wooded areas as much as
- Avoid the midslopes or the release zone near the top of the
- Detour completely around a suspect slope.
- If you must cross and avalanche slope, gather as much
information as you can about the snowpack. Probe the snow to see
if there is even resistance (if so the danger may be reduced). If
there is uneven resistance to the probe (breaks through a crust,
punches into layers of loose or unconsolidated snow) then the
avalanche danger may be high. Even better, find a safe location on
an adjacent slope with similar exposure, snow level and steepness
and dig a test pit. Look at the different layers. If you see
layers characterized by course, grainy, crystals, the slope is
probably not safe. If layers are firm and bonded it might
Crossing Avalanche Zones
- Remove ski pole straps and undo all pack buckles.
- Put on additional warm clothing in case of entrapment.
- Zip on and fasten all clothing securely to keep snow from
entering (cuffs, collars, etc.)
- Use avalanche cords or an avalanche beacon.
- Look at the crossing. Are there any islands of safety along
the way, a rock outcropping, a stretch of trees? If so, head to
the island of safety ASAP if a slide is triggered.
- Cross one at a time with all other group members watching.
- Yell to alert the group.
- Jettison your pack and head to an island of safety if
possible. Otherwise, try to stay on top of the snow using a
- Before the snow stops, try to make an air pocket in front of
your face by punching out the snow with your hands. Take a deep
breath to expand your chest before the snow settles. The snow will
quickly set like concrete. If your chest is not expanded, you may
not be able to breathe.
- Try to reach your hand to the surface to provide a clue for
rescuers (if you can tell where the surface is).
- If possible, try to dig yourself out.
- Watch the victim in the slide. Where was the person when they
were first hit by the slide (point A) and where were they when you
last saw them (point B)?
- Wait until the slope has settled and there is no indication of
further avalanche. You don't want to complicate the scenario with
- Mark point A and B on the slope with visible objects
- Visualize the line between point A and B. This is the path the
victim was swept down. Look for any clues on the surface
(clothing, skis, etc.) that might give more indication of the
person's position. Mark these spots.
- Turn your avalanche beacons to receive and begin search
- Probe the snow below point B. Stand shoulder to shoulder and
advance downslope in a line.
- If you locate the victim, dig them out quickly.
- Treat for hypothermia and shock.
- There is a good chance of head and spinal injuries in an
avalanche as well as fractures. Be careful moving the person.
- AMC Guide to Winter Camping, Stephen Gorman, AMC Books,
- The Avalanche Book, Betsey Armstrong and Knox Williams,
Fulcrum Publishing, Golden, CO, 1992.
- The ABC's of Avalanche Safety, E.R. LaChapelle, The
Mountaineers, Seattle, WA, 1985.
- Cold Metal
- Supercooled liquids - fuel
All of the above can lead to Hypothermia, Frostnip, Windchill,
Frostbite, Frozen Eyelashes/cornea
- Steep Terrain
- Avalanche - rare except for steep gullies (for east coast
- Gully Garbage - falling objects with sun, heat
- Breaking Through Ice - watch undercutting, watch margins of
ice to shore
- Moats - at objects, may be covered, watch margins of object to
- Tent Collapse - from snow loading
- "Widow makers"
- Stove Explosion
- Carbon Monoxide Poisoning - from stove use in tent
- Stove Burns - remember you are well insulated
- Dehydration - increases risk of hypothermia, frostbite
- Ice Axe/Crampon Injuries - "stabbing"
- Watermelon Snow - diarrhea
- Yellow Snow
- Poor Handwashing - food poisoning