MILITARY SURVIVAL MANUAL:VOL 9

UNITED STATES MARINE CORPS
Mountain Warfare Training Center
Bridgeport, California 93517-5001
WSVX.02.15
2/6/05
STUDENT HANDOUT
MOUNTAIN WEATHER
TERMINAL LEARNING OBJECTIVE In a cold weather mountainous environment, conduct
weather forecasting, in accordance with the reference. (WSVX.02.15)
ENABLING LEARNING OBJECTIVES
(1) Without the aid of references, describe in writing each type of cloud, in accordance
with the references. (WSVX.02.15a)
(2) Without the aid of references, state in writing the cloud progression for both a cold
and warm front, in accordance with the references. (WSVX.02.15b)
(3) Without the aid of references, state in writing five signs of nature, in accordance with
the references. (WSVX.02.15c)
OUTLINE
1 . G ENERAL
A. The earth is surrounded by the atmosphere, which is divided into several layers. The
world’s weather systems are in the troposphere, the lower of these layers. This layer
reaches as high as 40,000 feet.
B. Dust and clouds in the atmosphere absorb or bounce back much of the energy that the sun
beams down upon the earth. Less than one half of the sun’s energy actually warms the
earth’s surface and lower atmosphere.
C. Warmed air, combined with the spinning (rotation) of the earth, produces winds that
spread heat and moisture more evenly around the world. This is very important because
the sun heats the Equator much more than the poles and without winds to help restore the
balance, much of the earth would be impossible to live on. When the air-cools; clouds,
rain, snow, hail, fog and frost may develop.
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D. The weather that you find in any place depends on many things, i.e. how hot the air is,
how moist the air is, how it is being moved by the wind, and especially, is it being lifted
or not?
2 . P RESSURE
A. All of these factors are related to air pressure, which is the weight of the atmosphere at
any given place. The lower the pressure, the more likely are rain and strong winds.
B. In order to understand this we can say that the air in our atmosphere acts very much like a
liquid.
C. Areas with a high level of this liquid would exert more pressure on the Earth and be
called a “high pressure area”.
D. Areas with a lower level would be called a “low pressure area”.
E. In order to equalize the areas of high pressure it would have to push out to the areas of
low pressure.
F. The characteristics of these two pressure areas are as follows:
(1) H igh-pressure area. Flows out to equalize pressure.
(2) L ow-pressure area. Flows in to equalize pressure.
G. The air from the high-pressure area is basically just trying to gradually flow out to
equalize its pressure with the surrounding air; while the low pressure is beginning to
build vertically. Once the low has achieved equal pressure, it can’t stop and continues to
build vertically; causing turbulence, which results in bad weather.
NOTE: When looking on the weather map, you will notice that these resemble
contour lines. They are called “isobars” and are translated to mean, “equal
pressure area”.
H. I sobars. Pressure is measured in millibars or another more common measurement -
“inches mercury”.
I. Fitting enough, areas of high pressure are called “ridges” and areas of low pressure are
called “troughs”.
NOTE: The average air pressure at sea level is:
29.92 inches mercury.
1,013 millibars.
J. As we go up in elevation, the pressure (or weight) of the atmosphere decreases.
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EXAMPLE: At 18,000 feet in elevation it would be 500 millibars vice 1,013
millibars at sea level.
3. H UMIDITY. Humidity is the amount of moisture in the air. All air holds water vapor,
although it is quite invisible.
A. Air can hold only so much water vapor, but the warmer the air, the more moisture it can
hold. When the air has all the water vapor that it can hold, the air is said to be saturated
(100% relative humidity).
B. If the air is then cooled, any excess water vapor condenses; that is, it’s molecules join to
build the water droplets we can see.
C. The temperature at which this happens is called the “condensation point”. The
condensation point varies depending on the amount of water vapor and the temperature
of the air.
D. If the air contains a great deal of water vapor, condensation will form at a temperature of
20OC (68OF). But if the air is rather dry and does not hold much moisture, condensation
may not form until the temperature drops to 0OC (32OF) or even below freezing.
E. A diabatic Lapse Rate. The adiabatic lapse rate is the rate that air will cool on ascent and
warm on descent. The rate also varies depending on the moisture content of the air.
(1) Saturated Air = 2.2OF per 1,000 feet.
(2) Dry Air = 5.5OF per 1,000 feet.
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4. W INDS. As we stated earlier, the uneven heating of the air by the sun and rotation of the
earth causes winds. Much of the world’s weather depends on a system of winds that blow in
a set direction. This pattern depends on the different amounts of sun (heat) that the different
regions get and also on the rotation of the earth.
A. Above hot surfaces rising air creates a void. Cool air moves into and settles into the void.
The cool air is either warmed up and begins to rise or it settles. This is dependent upon
the sun’s thermal energy. The atmosphere is always trying to equalize between high
pressure and low pressure. On a large scale, this forms a circulation of air from the poles
along the surface or the earth to the equator, where it rises and moves towards the poles
again.
B. Once the rotation of the earth is added to this, the pattern of the circulation becomes
confusing.
C. Because of the heating and cooling, along with the rotation of the earth, we have these
surfaces winds. All winds are named from the direction they originated from:
(1) P olar Easterlies. These are winds from the polar region moving from the east. This
is air that has cooled and settled at the poles.
(2) P revailing Westerlies. These winds originate from approximately 30 degrees North
Latitude from the west. This is an area where prematurely cooled air, due to the
earth’s rotation, has settled back to the surface.
(3) N ortheast Tradewinds. These are winds that originate from approximately 30 degrees
North from the Northeast. Also prematurely cooled air.
D. J et Stream. A jet stream can be defined as a long, meandering current of high speed
winds near the tropopause (transition zone between the troposphere and the stratosphere)
blowing from generally a westerly direction and often exceeding 250 miles per hour. The
jet stream results from:
(1) Circulation of air around the poles and Equator.
(2) The direction of air flow above the mid latitudes.
(3) The actual path of the jet stream comes from the west, dipping down and picking up
air masses from the tropical regions and going north and bringing down air masses
from the polar regions.
NOTE: The average number of long waves in the jet stream is between three and five depending
on the season. Temperature differences between polar and tropical regions influence this. The
long waves influence day to week changes in the weather; there are also short waves that
influence hourly changes in the weather.
E. Here are some other types of winds that are peculiar to mountain environments but don’t
necessarily affect the weather:
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(1) A nabatic wind. These are winds that blow up mountain valleys to replace warm
rising air and are usually light winds.
(2) K atabatic wind. These are winds that blow down mountain valley slopes caused by
the cooling of air and are occasionally strong winds.
5. A IR MASSES. As we know, all of these patterns move air. This air comes in parcels
known as “air masses”. These air masses can vary in size from as small as a town to as large
as a country. These air masses are named for where they originate:
A. Maritime. Over water.
B. Continental. Over land.
C. Polar. Above 60 degrees North.
D. Tropical. Below 60 degrees North.
E. Combining these give us the names and description of the four types of air masses:
(1) Continental Polar. Cold, dry air mass.
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(2) Maritime Polar. Cold, wet air mass.
(3) Continental Tropical. Dry, warm air mass.
(4) Maritime Tropical. Wet, warm air mass.
F. The thing to understand about air masses, they will not mix with another air mass of a
different temperature and moisture content. When two different air masses collide, we
have a front which will be covered in more detail later in this period of instruction.
6. L IFTING/COOLING. As we know, air can only hold so much moisture depending on it’s
temperature. If we cool this air beyond its saturation point, it must release this moisture in
one form or another, i.e. rain, snow, fog, dew, etc. There are three ways that air can be lifted
and cooled beyond its saturation point.
A. O rographic uplift. This happens when an air mass is pushed up and over a mass of higher
ground such as a mountain. Due to the adiabatic lapse rate, the air is cooled with altitude
and if it reaches its saturation point we will receive precipitation.
OROGRAPHIC UPLIFT
B. C onvention effects. This is normally a summer effect due to the sun’s heat radiating off
of the surface and causing the air currents to push straight up and lift air to a point of
saturation.
6
CONVECTION EFFECTS
C. F rontal lifting. As we know when two air masses of different moisture and temperature
content collide, we have a front. Since the air masses will not mix, the warmer air is
forced aloft, from there it is cooled and then reaches its saturation point. Frontal lifting is
where we receive the majority of our precipitation. A combination of the different types
of lifting is not uncommon.
7. C LOUDS. (WSVX.02.15a) Anytime air is lifted or cooled beyond its saturation point
(100% relative humidity), clouds are formed. Clouds are one of our sign posts to what is
happening. Clouds can be described in many different ways, they can also be classified by
height or appearance, or even by the amount of area covered, vertically or horizontally.
A. C irrus. These clouds are formed of ice crystals at very high altitudes (usually 20,000 to
35,000 feet) in the mid-latitudes and are thin, feathery type clouds. These clouds can give
you up to 24 hours warning of approaching bad weather, hundreds of miles in advance of
a warm front. Frail, scattered types, such as “mare-tails” or dense cirrus layers, tufts are a
sign of fair weather but predictive may be a prelude to approaching lower clouds, the
arrival of precipitation and the front.
B. C umulus. These clouds are formed due to rising air currents and are prevalent in unstable
air that favors vertical development. These currents of air create cumiliform clouds that
give them a piled or bunched up appearance, looking similar to cotton balls. Within the
cumulus family there are three different types to help us to forecast the weather:
(1) Cotton puffs of cumulus are Fair Weather Clouds but should be observed for
possible growth into towering cumulus and cumulonimbus.
(2) Towering cumulus are characterized by vertical development. Their vertical
lifting is caused by some type of lifting action, such as convective currents
found on hot summer afternoons or when wind is forced to rise up the slope of
a mountain or possibly the lifting action that may be present in a frontal
system. The towering cumulus has a puffy and “cauliflower-shaped”
appearance.
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(3) Cumulonimbus clouds are characterized in the same manner as the towering
cumulus, form the familiar “thunderhead” and produce thunderstorm activity.
These clouds are characterized by violent updrafts which carry the tops of the
clouds to extreme elevations. Tornadoes, hail and severe rainstorms are all
products of this type of cloud. At the top of the cloud, a flat anvil shaped
form appears as the thunderstorm begins to dissipate.
C. S tratus. Stratus clouds are formed when a layer of moist air is cooled below its saturation
point. Stratiform, clouds lie mostly in horizontal layers or sheets, resisting vertical
development. The word stratus is derived from the Latin word “layer”. The stratus cloud
is quite uniform and resembles fog. It has a fairly uniform base and a dull, gray
appearance. Stratus clouds make the sky appear heavy and will occasionally produce fine
drizzle or very light snow with fog. However, because there is little or no vertical
movement in the stratus clouds, they usually do not produce precipitation in the form of
heavy rain or snow.
8. F RONTS. (WSVX.02.15b) As we know, fronts often happen when two air masses of
different moisture and temperature content interact. One of the ways we can identify that this
is happening is by the progression of the clouds.
A. W arm Front. A warm front occurs when warm air moves into and over a slower (or
stationary) cold air mass. Since warm air is less dense, it will rise naturally so that it will
push the cooler air down and rise above it. The cloud you will see at this stage is cirrus.
From the point where it actually starts rising, you will see stratus. As it continues to rise,
this warm air cools by the cold air and, this, receiving moisture at the same time. As it
builds in moisture, it darkens becoming “nimbus-stratus”, which means rain of
thunderclouds. At that point some type of moisture will generally fall.
B. C old Front. A cold front occurs when a cold air mass (colder than the ground that it is
traveling over) overtakes a warm air mass that is stationary or moving slowly. This cold
air, being denser, will go underneath the warm air, pushing it higher. Of course, no one
can see this, but they can see clouds and the clouds themselves can tell us what is
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happening. The cloud progression to look for is cirrus to cirrocumulus to cumulus and,
finally, to cumulonimbus.
C. O ccluded Front. Cold fronts move faster than warm ones so that eventually a cold front
overtakes a warm one and the warm air becomes progressively lifted from the surface.
The zone of division between cold air ahead and cold air behind is called a “cold
occlusion”. If the air behind the front is warmer than ahead, it is a warm occlusion. Most
land areas experience more
occlusions than other types of fronts. In the progression of clouds leading to fronts,
orographic uplift can play part in deceiving you of the actual type of front, i.e. progression
of clouds leading to a warm front with orographic cumulus clouds added to these. The
progression of clouds in an occlusion is a combination of both progressions from a warm
and cold front.
9. USING SIGNS FROM NATURE. (WSVX.02.15c) These signs will give you a general
prediction of the incoming weather conditions. Try to utilize as many signs together as
possible, which will improve your prediction. All of these signs have been tested with
relative accuracy, but shouldn’t be depended on 100%. But in any case you will be right
more times than wrong in predicting the weather. From this we can gather as much
information as needed and compile it along with our own experience of the area we are
working in to help us form a prediction of incoming weather. The signs are as follows:
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A. Contrail Lines. A basic way of identifying a low-pressure area is to note the contrail lines
from jet aircraft. If they don’t dissipate within two hours, that indicates a low pressure
area in your area. This usually occurs about 24 hours prior to an oncoming front.
B. Lenticulars. These are optical, lens-shaped cumulus clouds that have been sculpted by
the winds. This indicates moisture in the air and high winds aloft. When preceding a
cold front, winds and clouds will begin to lower.
C. An altimeter and map or a barometer can be utilized to forecast weather in the field.
However, the user must have operational knowledge of the gear.
D. A spider’s habits are very good indicators of what weather conditions will be within the
next few hours. When the day is to be fair and relatively windless, they will spin long
filaments over which they scout persistently. When precipitation is imminent, they
shorten and tighten their snares and drowse dully in their centers.
E. Insects are especially annoying two to four hours before a storm.
F. If bees are swarming, fair weather will continue for at least the next half day.
G. Large game such as deer, elk, etc., will be feeding unusually heavy four to six hours
before a storm.
H. When the smoke from a campfire, after lifting a short distance with the heated air, beats
downward, a storm is approaching. Steadily rising smoke indicates fair weather.
I. A gray, overcast evening sky indicates that moisture carrying dust particles in the
atmosphere have become overloaded with water; this condition favors rain.
J. A gray morning sky indicates dry air above the haze caused by the collecting of moisture
on the dust in the lower atmosphere; you can reasonably expect a fair day.
K. When the setting sun shows a green tint at the top as it sinks behind clear horizon, fair
weather is probable for most of the next 24 hours.
L. A rainbow in the late afternoon indicates fair weather ahead. However, a rainbow in the
morning is a sign of prolonged bad weather.
M. A corona is the circle that appears around the sun or the moon. When this circle grows
larger and larger, it indicates that the drops of water in the atmosphere are evaporating
and that the weather will probably be clear. When this circle shrinks by the hour, it
indicates that the water drops in the atmosphere are becoming larger, forming into clouds,
rain is almost sure to fall.
N. In the northern hemisphere winds form the south usually indicate a low-pressure system.
These systems are frequently associated with rainstorms. “Winds from the south bring s
rain in it’s mouth.”
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O. It is so quiet before a storm, that distant noises can be heard more clearly. This is due to
the inactivity of wildlife a couple of hours before a storm.
P. Natural springs tend to flow at a higher rate when a storm is approaching. This is due to
lower barometric pressure. This will cause ponds, with a lot of vegetative decay at the
bottom, to become momentarily polluted.
Q. A heavy dew or frost in the morning is a sign of fair weather for the rest of the day. This
is due to the moisture in the atmosphere settling on the ground vice in the form of
precipitation and up to 12 hours of continued good weather can be expected.
15-11
UNITED STATES MARINE CORPS
Mountain Warfare Training Center
Bridgeport, California 93517-5001
WSVX.02.16
2/6/05
STUDENT HANDOUT
INTRODUCTION TO EVASION
TERMINAL LEARNING OBJECTIVE In a cold weather mountainous environment,
demonstrate basic evasion techniques, in accordance with the references. (WSVX.2.16)
ENABLING LEARNING OBJECTIVES
(1) Without the aid of reference, list in writing the planning and preparation
considerations for evasion, in accordance with the references. (WSVX.2.16a)
(2) Without the aid of reference, describe in writing the definition of a Selected Area For
Evasion (SAFE), in accordance with the references. (WSVX.2.16b)
(3) Without the aid of reference, list in writing the steps taken during the occupation of a
SAFE, in accordance with the references. (WSVX.2.16c)
OUTLINE
1. PREPARING FOR A POTENTIAL EVASION SITUATION. The Code of Conduct
provides guiding principles to Marines involved in any military operation whether
peacekeeping, combat, or survival. An operation that deteriorates so severely that a Marine
unit is forced to employ survival skills may require that unit to “evade” hostile enemy units.
JP 3-50.3 defines evasion as the process whereby individuals who are isolated in hostile or
unfriendly territory avoid capture with the goal of successfully returning to areas under
friendly control. Should a survival situation require evading the enemy, success will depend
on prior planning.
a. P lanning and Preparation. (MSVX.12.16a) The responsibility for proper preparation
and planning for evasion ultimately rests with the individuals concerned. All Marines
who are tasked to execute any mission should receive the following:
(1) I ntelligence Briefings. Information on the mission route, enemy troop
dispositions, impact of enemy operations on friendly or multinational military
forces, status of the US or multinational military situation, or changing
attitudes of the enemy populace.
(2) E vasion Plan of Action (EPA). The EPA is one of the critical documents for
successful recovery planning. It is the vehicle by which potential evaders, prior
to their isolation in hostile territory, relay their after-isolation intentions to the
recovery forces. See Appendix D, “Evasion Plan of Action Format,” for
details on the content of an EPA.
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MSVX.2.16
(3) Selected Areas for Ev asion (SAFE) Area Intelligence Descriptions.
(WSVX.02.16b) A SAFE is a “designated area in hostile territory that offers
isolated personnel a reasonable chance of avoiding capture and of surviving
until they can be recovered.”
(a) They are designated by the Defense Intelligence Agency (DIA) and are
classified.
(b) Designed to facilitate extended evasion, which must meet certain
requirements for approval.
(4) E &R (Evasion and Recovery) Area Studies. E&R areas may be selected in any
geographic region based on operational or contingency planning requirements.
Although similar to SAFE areas in most respects, they differ in that not all
conventional selection criteria for SAFE areas can be met because of current
political, military, or environmental factors prevailing in the country.
(5) S urvival, Evasion, Resistance, and Escape Guides and Bulletins. They contain
the basic information to help an individual survive, successfully evade and, if
captured, resist enemy exploitation. These bulletins cover information on
topography and hydrography, food and water sources, safe and dangerous
plants and animals, customs and cultures.
(6) I solated Personnel Report (ISOPREP). When filled in, the DD Form 1833 is
classified CONFIDENTIAL. It enables a recovery force to authenticate
evaders.
2. E XECUTING AN EVASION PLAN OF ACTION (EPA). Unforeseen circumstances may
require Marines to execute their EPA.
a. I nitial Planning. Immediately upon breaking contact, attempt to gain maximum
distance between yourself and the enemy.
(1) Carefully consider METT-T during all planning and execution.
(2) Determine unit’s combat effectiveness.
(3) Develop a course of action.
b. M ovement techniques. If possible, the entire movement to friendly or neutral areas, as
well as to designated SAFE areas or E&R areas should be completed without being
observed. Furthermore, an appreciation of the methods by which a hostile force may
attempt to detect you will assist in techniques to maximize your concealment.
(1) M ethods to avoid enemy detection.
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MSVX.2.16
(a) Apply standard patrolling movement techniques.
(b) Avoid natural lines of drift and Main Supply Routes (MSR).
(c) Avoid all rural areas, small towns, and farms.
-Dogs and domestic poultry are very common and will provide a
“first alert” needed to initiate a hostile search.
(2) M ethods of detecting the evader.
(a) Direct Observation.
(b) Detection Equipment.
-Thermal imaging
-Active Infrared (IR), such as NVGs
-Acoustic detectors/sensors
-Direction finding equipment for radios
(c) Search teams.
-Military and/or civilian
-Trackers
(d) Dogs.
-Attack or tracking dogs
-Difficult to determine if being tracked by dogs
-Attempt to discourage the dog from doing its job
c. O ccupation of a SAFE or E&R. (WSVX.02.16c) Prior to movement to, and
occupation of a SAFE or E&R area, consider the following:
(1) Conduct a reconnaissance of the entire area for enemy threat. This may me a
physical or visual reconnaissance.
(2) Select an occupation site which affords:
(a) Concealed escape routes if detected by enemy.
(b) Close proximity to a potential extraction site.
(c) Observation of the area and avenues of approach.
(3) Apply the requirements for survival.
(4) Execute the communication and signaling plan as ordered.
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MSVX.2.16
REFERENCE.
1. JP 3-50.3, Joint Doctrine for Evasion and Recovery, 1996.
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MSVX.2.16
UNITED STATES MARINE CORPS
Mountain Warfare Training Center
Bridgeport, California 93517-5001
WSVX.01.01
2/6/05
STUDENT HANDOUT
AVALANCHE AND ICE HAZARDS
LESSON PURPOSE. The purpose of this period of instruction is to introduce the student to
avalanche and ice hazards, their characteristics, dangers, and how to protect yourself from them.
OUTLINE
1. T YPES OF AVALANCHE: There are four types of avalanches: Loose-snow, Slab, cornice
collapse and Ice.
a. L oose-snow Avalanches. Sometimes called point release slides, they start when a
small amount of cohesion less snow breaks away and starts to descend down the
slope. At a distance it will appear to look like they start from a point and fan out as
they descend. They will start out small and usually involve only the top layers. This
avalanche is capable of being quite large and destructive depending on the amount of
material it will entrain during its descent.
(1) The stress this avalanche creates during its descent may be enough to trigger
larger and deeper slab releases
(2) It occurs more often on steep slope angles of 35 degrees or higher.
(3) It will range in speeds up to 200 mph.
b. S lab Avalanches. These avalanches occur when one or more layers of cohesive snow
break away from a sloped snowfield at the crown surface. As the slabs travel down
slope, they break up into smaller blocks or clods.
(1) Slab avalanches begin when the force of gravity pulling a layer or layers of snow
downhill exceeds the strength of the weakest layer in the snow pack.
(2) Slabs vary in size from just a few inches to many feet thick, and range in width
from a few yards to over a mile. Slab material is also highly variable; slabs may be
hard or soft, wet or dry.
(3) Will range in speeds up to 150 mph.
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WSVX.01.01
(4) Features of a slab avalanche.
(a) Crown Face / Fracture Line. This is the upper boundary of the slab.
(b) Crown. This area is immediately above the crown face/fracture
line.
(c) Flanks. This is the outer boundaries of the slab.
(d) Stauchwall. This is the bottom boundary of the slab.
(e) Bed Surface. The sliding surface for the avalanche.
(5) Slope angle. Slab avalanches originate on a wide variety of terrain. The main
requirement is slope angle. Most slabs fracture on slope angles between 35-40
degrees.
(a) Slopes less than 30 degrees are less likely to have slab avalanches
because there isn’t enough tension of on the slab area.
(b) Slopes greater than 45 degrees usually sluff before slabs can form.
c. C ornice Collapses. An overhang of snow forms when windblown snow builds out
horizontally at sharp terrain-breaks such as ridge crests and the sides of gullies. They
can break off well back from the edge, and often trigger bigger slides when they hit
the wind-blown pillowed area of the slope.
d. I ce Avalanches. These are caused by the collapse of unstable ice blocks (seracs) from
steep or overhanging parts of a glacier. Ice avalanches can entrain a large amount of
rock, ice, and snow and travel long distances. These avalanches are not predictable
and cannot be detected.
2. AVALANCHE TRIGGERS. There are two types: natural and artificial.
a. N atural Triggers. These are not triggered directly by man or his equipment. A falling
cornice, sluffing snow, stress change due to metamorphism, avalanche, etc., can all
trigger avalanches.
b. A rtificial Triggers. Man or his equipment triggers these. A ski pass, a mountaineer's
weight, an explosive blast, a sonic boom, etc., commonly set off avalanches.
3. PARTS OF AN AVALANCHE
a. S tarting zone. It is usually steeper than 30 degrees and receives large amounts of
snow. This is where the unstable snow breaks loose and starts to slide.
b. A valanche Track. Refers to the path under the starting zone and above the run out
zone. They can be channeled or unchanneled. The track is the slope or channel down
which snow moves.
(1) Channeled tracks are confined areas such as gullies and couloirs. Unconfined
tracks are on open slopes. Some may have trees present.
(2) An avalanche track may have several branches or several small tracks having
separate starting zones that may feed into one big track. It is important to
remember that multi-branch tracks may run several times in quick succession.
A number of rescuers have been killed when working a run out zone and a
second avalanche ran down within hours of the first avalanche.
(3) Wet snow avalanches tend to follow the track boundary, whereas dry snow
avalanches can easily jump terrain barriers.
c. R un out zones. This is the area at the bottom of the path where debris piles-up.
Variation in weather patterns from one year to the next will influence the position of
the run out zone. This is where the snow and debris slows down and comes to rest
4. AVALANCHE HAZARD EVALUATION PROCESS. The evaluation process is the
interaction of four critical variables, which helps determine whether or not, an avalanche is
possible. They are snow pack, weather, terrain, and the human factor.
a. T he Snow Pack. Is the snow capable of sliding? As each storm passes, a new layer of
snow is added, some by the wind some not, and every layer of snow has it’s own
texture and strength. Some layers will be strong while some will be weak. Some will
bond well, and some won’t. Although the study of snow metamorphism is a science,
Marines must determine if a weak bond in the snow pack exists. Additionally, one
must attempt to estimate the amount of snow that could be potentially released, if
triggered.
b. T he Weather. Is the weather contributing to instability? It is an observed fact that all
natural avalanches occur during or shortly after a storm. Why? The snow pack can’t
handle the new weight being added. This new weight alters the balance in strength
and stress. The three main contributing factors are the precipitation, wind, and
temperature.
(1) Signs of Instability.
(a) Recent avalanche activity on similar slopes and small avalanches
underfoot.
(b) Booming. The audible collapse of snow layers.
(c) Visible cracks shooting out from underfoot.
(d) Sluffing debris, which is evidence of avalanche activity occurring.
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WSVX.01.01
(e) Sunballing, which is caused by rapid warming of the snow surface.
(f) Weather patterns.
1. Heavy amount of snow loading in a short period of time. (1
in/hr for 24 hr period).
2. Heavy rains which warms and weakens the snow pack.
3. Significant wind loading causing leeward slopes to possibly
become overloaded.
4. Long, cold, clear, calm period followed by heavy precipitation
or wind loading.
5. Rapid temperature rises to above freezing after long a cold
period.
6. Prolonged periods (e.g. more than 24 hrs) of above-freezing
temperatures.
7. Cold snow temperatures (equal to or less than 25F) slow down
the settlement or strengthening process, thus allowing unstable
snow conditions to persist longer.
(2) Signs of Stability.
(a) Snow cones or settlement cones form around trees and other obstacles
and indicate the snow around the object is settling.
(b) Creep and Glide. Creep is the internal deformation of the snow pack.
Glide is slippage of the snow layer with respect to the ground.
Evidence of these two properties on the snow pack is a ripple effect at
the bottom of a slope. It is an indication that the snow is gaining
equilibrium and strength through this type of settlement process.
(c) Absence of wind during storms which is indicated by snow
accumulation in the trees.
(d) Snow temperatures remaining between 25 & 32F ordinarily settles
snow rapidly, creating a denser and stronger snow pack.
c. T he Terrain. Being able to recognize avalanche terrain is a critical step in the
evaluation process. Assuming that avalanches occur on only big slopes is a very
common mistake. Avalanches can occur on any slope.
(1) S lope Angle. Slope angle should always be factored when planning
movements in snow covered mountainous terrain.
(a) As the slope angle increases, so does the stress on the boundary
regions of a slab.
(b) Most slab avalanches release on slopes with angles between 35-40
degrees.
(c) Loose snow avalanches occur on high angle slopes 60 degrees and
above.
(2) Slope Orientation.
(a) Leeward, wind-loaded slopes tend to increase the stress on the snow
pack.
(b) Snow packs moderately hit by the sun can strengthen and stabilize the
snow pack.
(c) Direct sunlight has the opposite effect by weakening and lubricating
the bonds between grains.
(d) Weak layers are often well developed or persist on shaded slopes due
to the colder conditions and absence of solar warming during the
winter. Suspect instability on these slopes.
(3) Terrain Roughness (Anchoring). Slopes with anchors are less likely to
avalanche than open slopes.
(4) V egetation. The most convincing evidence of past avalanche activity is a path
of fallen trees, aligned in the same direction and sheared at the height above
the ground.
(a) Trees void of branches on the uphill side, which are called “flagged”
trees.
(b) Cleared strips of trees in a dense forest.
(5) S easonal. Once an avalanche path has begun to slide in a season, other
avalanches may occur a long the same path.
(6) E levation. Temperature, wind and precipitation often vary significantly with
elevation. Common differences include rain at lower elevations or differences
in precipitation amounts, or wind speed with elevation. Never assume that
conditions on a slope at a particular elevation reflect those of a slope at a
different elevation.
(7) L ocal Population. A good source of information but beware of short-term
observations, i.e., 10 years.
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d. The Human Factor. What are your alternatives and their possible consequences?
e. Hazard Evaluation. This should be an on going process, and should start before the
mission even begins.
(1) B efore. Gather information on the weather such as new snowfall, high winds,
snow advisories, and topography of the terrain. Find out any past history of the
area and recent or past avalanche activity.
(2) D uring. During your movement, try and fine-tune any information that may
help in your decision-making process and support the fact that there may be an
avalanche hazard.
(3) B e Objective. We don’t have options when assigned missions. You have to
look at the overall mission with the present avalanche hazard to determine
whether you should continue on or choose an alternate route.
5. ROUTE CONSIDERATIONS.
a. Determine starting zones of probable avalanche prone slopes and cross as high as
possible, preferably above natural anchors.
b. Travel on high points and ridges, especially windward sides.
c. When ascending or descending an avalanche prone slope, stay to the side of the start
zone and track.
d. Avoid wind-loaded, lee slopes.
e. Favor terrain with anchors, i.e. tree-covered areas over open slopes.
f. Pick areas with flat, open run-outs so that debris burial depth is decreased. Avoid
areas that feed into crevasses and cliffs.
g. You can generally find a safe route somewhere in a wide U-shaped valley, but narrow
V-shaped ones should be avoided. In V-shaped valleys, avalanches could run from
either side and continue up the opposite side, so there may be little or no safe ground.
6. CROSSING AVALANCHE PRONE SLOPES. Certain requirements may make it
necessary to cross a suspected slope. This should be done only AFTER all alternatives have been
exhausted.
a. Individual Preparation.
(1) Loosen ski bindings; remove hands from ski pole straps.
(2) Leave your pack on and secure the pack straps.
(3) Secure ECWCS hood tightly covering face, trail an avalanche cord if
available.
(4) Go straight downhill on foot rather than ski and look for possible escape
routes.
(5) Go straight down, do not traverse.
(6) If possible cross as high as possible on concave slopes.
(7) Cross one at a time and if one crosses safely, it does not mean that it is safe
passage for the rest. If possible, belay everyone across.
b. Actions if Caught.
(1) Attempt to remove skis or snowshoes.
(2) Assess best line of escape.
(3) Delay your departure, i.e., let as much of the avalanche pass you as possible.
(4) Try and work to the side. There will be less force of the avalanche at the edge
of the flow.
(5) Try to swim out using a double action backstroke or try to roll away at a 45-
degree angle.
(6) A supreme effort should be made to get to the surface as the avalanche settles.
(7) Make an air space to breath.
(8) Move to position near the surface if possible.
(9) Establish orientation.
(10) Don’t panic.
c. Avalanche Rescue. Statistically, after about 1/2 hour of burial, the chance of survival is
approximately 50%. After an hour the chances of survival drop to 20%. Speed is
therefore essential for recovering a live victim. Cold and suffocation is the main
causes of death.
(1) Make a careful note of where he was last seen and mark the spot. Also mark
any position where he reappeared during his movement.
(2) Make a quick visual search of the area, looking for any sign (i.e., avalanche
cord, body parts, or equipment).
(3) If nothing is apparent at first then make a quick surface search.
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(4) If nothing is found, a more systematic search should be made from the bottom
working up.
(5) If you again fail to find anything, your next step is to probe.
(6) Most Likely Spots to Find an Avalanche Victim.
(a) Start at the last seen location and work down the slope. Look for clues
of the victim such as skis, clothing, avalanche cord, etc.
(b) At the outsides of bends of the avalanche path where debris
accumulates.
(c) Look on the uphill side of obstacles, such as trees and boulders, where
debris builds up.
(d) In the run out zone, debris may be very large and hard to search.
(7) Types of Searches. This will depend on manpower available and time.
(a) H asty search. By far the most important search for backcountry travel.
Speed is essential and the determination whether or not to go for help
is a difficult one.
(b) C oarse probe. The idea behind this type of probe is to sacrifice some
thoroughness for speed.
(c) F ine probe. Takes 4-5 times longer than the coarse probe. Chances
are, the victim will not be recovered alive.
7. ICE HAZARDS. Frozen waterways (lakes, streams, and bays) can be life threatening
obstacles when crossing. Ice is classified in three general types: salt water, fresh water, and
land.
a. F resh Water Ice. Fresh water ice begins to form on lakes and rivers under normal
conditions, from 3-5 weeks after the daily temperature drops below 32F.
b. L ake Ice is generally weak in the areas of streams, inlets, springs, or outlets.
Decaying vegetation on the bottom of a lake may give off air bubbles, which slow ice
formation and create weak ice.
c. R iver Ice formed by warm weather and wind may create a rough surface, which will
remain ruff throughout the winter. This ice is filled with air bubbles.
d. Normally, fresh water does not freeze to a thickness greater than 8 feet in a single
season. In lakes, the normal ice depth by late March is between 3 1/2 feet and 6 feet,
depending on winter temperatures.
(1) The following conditions will speed up freezing:
(a) Low stable temperatures.
(b) High wind-chill factor.
(c) No snow cover.
(d) No current.
(2) The following conditions will retard freezing:
(a) Fluctuating temperature.
(b) Fast current.
(c) Snow cover.
(d) Salt water and other impurities.
NOTE: The strength of ice depends upon ice structure, purity of water, freezing process, cycles
of freezing and thawing, crystal orientation, temperature, ice thickness, snow cover, water
current, underside support, and age.
e. S pecial Considerations.
(1) Immediately adjacent to the shore, the ice formation is thin and weak and
more likely to develop cracks than ice in the center of a frozen stream.
Depending upon the gradient of the riverbed and the thickness of the ice near
the shore, it is generally safer to maintain a route near the shore if the ice rests
upon the river bottom.
(2) Where an under-ice current of water flows under a large ice area, the ice in
contact with the current is subject to a greater variation in temperature over a
given time, and therefore thicker than the ice in adjacent areas.
(3) Shallow water ice is usually thinner than deep water ice.
(4) Good quality ice is clear and free from bubbles and cracks. In a body of water
containing clear and cloudy ice. The clear ice will frequently be thinner then
the cloudy ice.
(5) Lakes containing a great deal of vegetation whose decomposition retards
freezing, results in weak ice.
(6) Flooded snow when frozen produces "slush ice" which is white and may
contain air bubbles. Slush ice has a load carrying capacity approximately 1/4
less than that of prime natural ice.
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(7) Ice that remains unsupported after a drop in the water beneath it has little
strength. Reservoirs and lakes with runoffs are examples.
8. ICE CROSSING.
a. S afety Precautions. There are six safety precautions to take prior to crossing an icecovered
body of water.
(1) Loosen bindings on skis or snowshoes, if so equipped.
(2) Remove wrist loops of ski poles, if so equipped. If ski poles are not available,
attach a wrist loop to a fixed blade knife (i.e., bayonet) and fasten to the arm.
(3) Clothing should be worn snugly. All ties tied securely (wrist straps, waist
straps, collars, trouser cuffs, etc.) This gives buoyancy if break through
occurs, and reduces cold shock.
(4) Sling pack and weapons onto one shoulder.
(5) Only expose one man to the danger at a time or until weight factor is
determined.
(6) Ropes should belay the first group of individuals, if available.
b. S elf-Rescue Techniques. If an individual or group breaks through the ice, carry out
the following techniques.
(1) Remove unnecessary gear (packs, weapons, snowshoes, etc.) and attempt to
throw them onto the ice.
(2) Use your fixed blade knife or ski pole (if equipped) to drag/push yourself out
of the water.
(3) Do not stand up near the hole. Remain flat and continue to push/drag yourself
away from the hole until clear of the danger.
(4) R EWARM IMMEDIATELY. Cold-water immersion will result in shock
and hypothermia. Strip all wet clothing off and attempt to rewarm body with a
dry sleeping bag or as many fires as possible, surrounding the body.
c. G roup-Rescue Techniques. If personnel are available to assist in the rescue, carry out
the following techniques.
(1) Do not allow Marines to move near the hole without some type of safety (i.e.,
rope, human chain).
(2) If rope is available, tie a large fixed loop on the end. Throw the loop to the
victim and have him place the loop over the body.
(3) If rope is not available, locate a long stick and create a human chain. With all
Marines lying prone, move the chain to as close as possible until the victim
can grasp the stick.
(4) If the victim cannot grasp the stick, continue to edge the chain to the hole until
the end man can reach the victim by hand.
(5) Once the victim has been recovered, REWARM IMMEDIATELY.
REFERENCE:
1. Jill Fredston, Snow Sense, 1994.
2. CRREL Technical Publication, Ice Dynamics MP 1585, 1975.
3. CRREL Technical Publication, Ice Reconnaissance SR 91-30, 1990.
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