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Mid June to Late September.

The access road turns off Highway 70 about 26km's after Waiau.

From the Mt Lyford Lodge it is a 8km long well maintained gravel road which passes through native Beach Forest and into alpine terrain. It passes through the lower of the two areas at Mount Lyford, Lake Stella the original ski area, from here it is a easy drive to the Mt Terako Basin, this is where you will find the Ski Area.

Terrain Features & Snowgroomers:

Resort Facilities:

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Mid June to Late September. The access road turns off Highway 70 about 26km's after Waiau. From the Mt Lyford Lodge it is a 8km long well maintained gravel road which passes through native Beach Forest and into alpine terrain.

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Every year, hundreds of people are hospitalised for hypothermia. Largely, it's a result of not being prepared.

Ever-intrepid Story reporter Lachlan Forsyth decided to get very cold in the name of education.

First, Lachlan swallowed a pill that would record his temperature. Then he sat in a stream on Wellington's south coast during a freezing northerly.

There was warm clothing ready to go, as well as a medic, a hypothermia expert and a member of the Mountain Safety Council -- just in case things turned pear-shaped.

Hypothermia expert Jim Cotter says getting wet is a big risk factor when it comes to hypothermia.

"[A] number of New Zealand streams have got slippery rocks, and you're hopping up the stream and you slip and you're straight in. You could be lying there injured and you couldn't get out."

Once wet and cold, the body's core temperature starts to drop and shaking sets in.

Mild hypothermia is when the body's core drops to 35degC. People with mild hypothermia will shiver, may appear drunk and could deny there's a problem.

The body churns through calories at a rate six times faster than normal in an attempt to keep the body temperature up.

From here, the "umbles" set in -- stumbling, grumbling and mumbling. They are often coupled with increased breathing and heart rate.

Symptoms of severe hypothermia are muscle stiffness, shivering stops, collapse, unconsciousness, cardiac arrest and even death.

For Lachlan, his body fought to keep warm for two hours before he started running low on energy. That's when his temperature dropped.

If you come across someone suffering from hypothermia, here's what you should do:

1. Find shelter. 2. Remove and replace wet clothes. 3. Assist rewarming. 4. If they are unconscious, place them in the recovery position. 5. Monitor them, and call for help.

Watch the video for the full Story report.

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Every year, hundreds of people are hospitalised for hypothermia. Largely, it's a result of not being prepared. Ever-intrepid Story reporter Lachlan Forsyth decided to get very cold in the name of education. First, Lachlan swallowed a pill that would record his temperature. Then he sat in a stream on Wellington's south coast during a freezing northerly.

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Rules and responsibilities

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And good to know the grades so you don't get out of your depth difficulty wise.

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Need to build an emergency shelter in the snow? Do you intend to camp out in the snow on a ski trek? Or are you trying to build the best snow fort your town has ever seen? Just want to relax? No matter what your reason is, make sure you...

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Also some very good to know stuff....

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How to Snowboard - Online Snowboard Lessons - Mechanics of Snowboarding

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Handy to know a little something prior to heading out there.....

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How to Ski - Online Ski Lessons - Mechanics of Skiing

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Some information about the various conditions you may get on the ski field.

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Depending on how cold it is, warm it is, windy it is, when it snowed the last time, how much it snowed the last time, and many many more variables, there can be lots of different conditions on the mountain. Here is a brief introduction to some of them:

Snow Conditions

Icy Pistes

If it is cold and has not snowed for a while, the pistes will start to get quite icy, this is because skiers and snowboarders keep going over the same layer of snow compacting it more and more until it becomes very solid. Most skiers and boarders do not like ice as they can not dig their edges into it very well, and have very little control. However if the ice is all smooth, and there is plenty of room, ice can be a lot of fun, and the ultimate piste condition for speed skiing.

Soft Pistes

If it has snowed recently, even though the piste machines (piste bashers) will have compacted and flattened the snow, the snow will still be relatively soft. In these conditions the snow can be moved around a lot, and pistes can become very lumpy very quickly. This is when the moguls really start to be made. With the soft snow though the skis will normally have a lot of control as the edges can dig into the snow well, and it will also generally not hurt so much if you fall over.

Slushy Pistes

If it is too warm and the snow melts in the day, and then refreezes in the night, you will find that it is extremely icy in the morning, and as the day goes on the snow will start to melt, and become slushy. As the snow keeps melting and refreezing, all the snow flake structure is lost, and what is left is lots of little lumps of ice, so if you fall you will get ice burns on bare skin. Because there is no snow crystal structure in slush, slushy snow is very heavy, and can make the skis very hard to turn and move around. When the snow is wet, the water will also start to create a vacuum between the ski and the snow, sucking the ski to the snow so that it can not slide so easily. Slush is generally not a preferred snow condition, although it can still be fun. These conditions are more common at the end of a season in the spring.

Sticky Snow

When snow is wet it can start to create a vacuum under the ski which stops the skis from sliding so easily, as can happen with slush. The worst snow for this though is generally fresh snow that still has the snow crystal structure but which is melting rapidly and starting to become wet very quickly. Because of the fine wet structure of the snow it moulds itself to the bottom of the ski very tightly making it very hard for air to get underneath. This creates a vacuum that makes it very difficult for the ski to slide. Skiing in this kind of snow can be very frustrating as skis can simply not slide across slopes that they normally would, and even skiing down steeper slopes can feel like someone has put the brakes on.

Each of theses conditions can obviously be more or less extreme, and it is also possible to get a mixture of the conditions. For instance if there has been a fresh snowfall on an icy piste, the fresh snow can be pushed off the ice in places, leaving icy patches amongst a softer piste.

Weather Conditions

Sunny Weather

Sunny weather is generally the nicest weather to ski in as you can see where you are going easily, you can see the definition in the snow, with the bumps and changes in gradient easy to make out, and you can enjoy the views on the mountain. If it is a beautiful clear day and nice and sunny, it does not necessarily mean that it is going to be warm or even warmer though.

The sunny days can be some of the coldest, especially if it is the middle of winter. Fortunately as there will not be so much moisture in the air, you should retain your heat a bit better than in some other conditions. In general though, the sunny days are the warmer days and they can be extremely warm especially in the spring. Towards the end of the season it is even possible to go skiing in a tshirt it can be that warm, although you should be careful if you consider this as falling on bare skin can give you ice burns very easily.

Blizzard

A blizzard is the most dangerous condition on the mountain. It is when there is a strong wind and it is snowing heavily. In a blizzard you can not see very well, the snow and moisture in the air makes you lose heat quickly, and the wind just keeps throwing more snow and cold air at you, making you cold even more quickly. There are many different intensities that a blizzard can be, but if it is a stronger blizzard no-one in their right mind stays on the mountain, unless they really must i.e. they're stuck. Skiing in a severe blizzard is no fun for anyone.

White Out

A white out can be a blizzard or just a very misty day, and is basically where the weather stops you from seeing very far. In a bad white out you won't be able to see more that a few metres away from you. This can make navigating a slope extremely difficult, especially for someone who doesn't know the slope very well.

It can also be easy to go off the side of the piste without realising in places as you can not see where the edge is if there are no markers nearby. Again skiing isn't much fun if it's a really bad whiteout, as you just can't do much. Although very rare, some people are unlucky enough, to only have a white out for the whole of their holiday, and never get to see what the mountain actually looks like.

Flat Light

Flat light is where there is a thick layer of cloud in the sky, and the light bounces through the clouds so that it comes from all directions, creating no shadows on the snow. Since the snow is all white, you can not see any definition without shadows and different light intensities, this means that you can't see bumps, changes in gradient, or basically any shapes in the snow. When skiing in flat light it is advised to stay below the tree line if possible, as the trees give more definition to the snow, and act as features near the piste to use as references. Using the correct lenses in your goggles will also help a lot with seeing definition in the snow as explained in the goggles page. Skiing closer to the side of the piste can also help as you can use piste signs and other features as references. If you don't have much to help you determine what the piste does, it can be very hard skiing in flat light. It is hard to prepare for anything that comes up, as you don't know it's coming, sometimes you just have to hit it and hope you can recover. It can also be very hard to tell how fast you are going, you might think you are going really fast when you are barely moving, or think you are barely moving when you are actually really going some, you might not be able to tell. Also if you jump you can not always see when you are going to land, if that's the case you just have to try and be ready for it.

Changeable Conditions

It is very common for the weather conditions on the mountain to change during the day, or to even have several different weather conditions at the same time. This should not be underestimated as the weather can both change extremely quickly, and have two or more different extremes at the same time. In the picture here you can see how extreme sun turns into a complete white out as you go into the clouds. If the weather is likely to change at all it is very important to be prepared for it and have whatever extra equipment and clothing you would need with you.

Sunburn

Please also be aware that it is also very easy to get sun burnt on a mountain. The sunlight reflects off of the snow and gives you a lot more exposure to the sun than you might realise. Adding this to the fact that you are high up on a mountain and there is less atmosphere to stop the suns rays before they get to you as well, you must be careful. Even in conditions where you can't even see the sun properly it can still be very easy to get sun burnt.

Although many people love different types of conditions, almost all prefer it to be reasonably sunny with good light. The people who prefer bad light will generally be the people who want the snow to themselves, and prefer that over being able to see properly.
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Depending on how cold it is, warm it is, windy it is, when it snowed the last time, how much it snowed the last time, and many many more variables, there can be lots of different conditions on the mountain.

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A risk for us or do Lyford staff look after that part?

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The terminus of an avalanche in Alaska's Kenai Fjords.

An avalanche is a rapid flow of snow down a slope, such as a hill or mountain.

Avalanches can be set off spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earthquakes. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees.

Avalanches occur in two general forms, or combinations thereof: slab avalanches made of tightly packed snow, triggered by a collapse of an underlying weak snow layer, and loose snow avalanches made of looser snow. After being set off, avalanches usually accelerate rapidly and grow in mass and volume as they capture more snow. If an avalanche moves fast enough, some of the snow may mix with the air, forming a powder snow avalanche.

Though they appear to share similarities, avalanches are distinct from slush flows, mudslides, rock slides, and serac collapses. They are also different from large scale movements of ice.

Avalanches can happen in any mountain range that has an enduring snowpack. They are most frequent in winter or spring, but may occur at any time of the year. In mountainous areas, avalanches are among the most serious natural hazards to life and property, so great efforts are made in avalanche control.

There are many classification systems for the different forms of avalanches, which vary according to their users' needs. Avalanches can be described by their size, destructive potential, initiation mechanism, composition, and dynamics.

Most avalanches occur spontaneously during storms under increased load due to snowfall and/or erosion. The second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall. Artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Contrary to popular belief, avalanches are not triggered by loud sound; the pressure from sound is orders of magnitude too small to trigger an avalanche.

Avalanche initiation can start at a point with only a small amount of snow moving initially; this is typical of wet snow avalanches or avalanches in dry unconsolidated snow. However, if the snow has sintered into a stiff slab overlying a weak layer then fractures can propagate very rapidly, so that a large volume of snow, that may be thousands of cubic metres, can start moving almost simultaneously.

Slab avalanches form frequently in snow that has been deposited, or redeposited by wind. They have the characteristic appearance of a block (slab) of snow cut out from its surroundings by fractures. Elements of slab avalanches include the following: a crown fracture at the top of the start zone, flank fractures on the sides of the start zones, and a fracture at the bottom called the stauchwall. The crown and flank fractures are vertical walls in the snow delineating the snow that was entrained in the avalanche from the snow that remained on the slope. Slabs can vary in thickness from a few centimetres to three metres. Slab avalanches account for around 90% of avalanche-related fatalities in backcountry users.

The largest avalanches form turbulent suspension currents known as powder snow avalanches or mixed avalanches, a kind of gravity current. These consist of a powder cloud, which overlies a dense avalanche. They can form from any type of snow or initiation mechanism, but usually occur with fresh dry powder. They can exceed speeds of 300 km/h (190 mph), and masses of 10,000,000 tonnes; their flows can travel long distances along flat valley bottoms and even uphill for short distances.

An ice avalanche occurs when a large piece of ice, such as from a serac or calving glacier, falls onto ice (such as the Khumbu Icefall), triggering a movement of broken ice chunks. The resulting movement is more analogous to a rockfall or a landslide than a snow avalanche. They are typically very difficult to predict and almost impossible to mitigate.

As an avalanche moves down a slope it follows a certain pathway that is dependent on the slope's degree of steepness and the volume of snow/ice involved in the mass movement. The origin of an avalanche is called the Starting Point and typically occurs on a 30-45 degree slope. The body of the pathway is called the Track of the avalanche and usually occurs on a 20-30 degree slope. When the avalanche loses its momentum and eventually stops it reaches the Runout Zone. This usually occurs when the slope has reached a steepness that is less than 20 degrees. These degrees are not consistently true due to the fact that each avalanche is unique depending on the stability of the snowpack that it was derived from as well as the environmental or human influences that triggered the mass movement.

People caught in avalanches can die from suffocation, trauma, or hypothermia.

From "1950-1951 to 2020-2021" there were 1,169 people who died in avalanches in the United States. For the 11-year period ending April 2006 445 people died in avalanches throughout North America. On average, 28 people die in avalanches every winter in the United States.

In 2001 it was reported that globally an average of 150 people die each year from avalanches. Three of the deadliest recorded avalanches have killed over a thousand people each.

Terrain, snowpack, weather

Avalanche formation requires a slope shallow enough for snow to accumulate but steep enough for the snow to accelerate once set in motion by the combination of mechanical failure (of the snowpack) and gravity. The angle of the slope that can hold snow, called the angle of repose, depends on a variety of factors such as crystal form and moisture content. Some forms of drier and colder snow will only stick to shallower slopes, while wet and warm snow can bond to very steep surfaces. In particular, in coastal mountains, such as the Cordillera del Paine region of Patagonia, deep snowpacks collect on vertical and even overhanging rock faces. The slope angle that can allow moving snow to accelerate depends on a variety of factors such as the snow's shear strength (which is itself dependent upon crystal form) and the configuration of layers and inter-layer interfaces.

The snowpack on slopes with sunny exposures is strongly influenced by sunshine. Diurnal cycles of thawing and refreezing can stabilize the snowpack by promoting settlement. Strong freeze-thaw cycles result in the formation of surface crusts during the night and of unstable surface snow during the day. Slopes in the lee of a ridge or of another wind obstacle accumulate more snow and are more likely to include pockets of deep snow, wind slabs, and cornices, all of which, when disturbed, may result in avalanche formation. Conversely, the snowpack on a windward slope is often much shallower than on a lee slope.

Avalanches and avalanche paths share common elements: a start zone where the avalanche originates, a track along which the avalanche flows, and a runout zone where the avalanche comes to rest. The debris deposit is the accumulated mass of the avalanched snow once it has come to rest in the run-out zone. For the image at left, many small avalanches form in this avalanche path every year, but most of these avalanches do not run the full vertical or horizontal length of the path. The frequency with which avalanches form in a given area is known as the return period.

The start zone of an avalanche must be steep enough to allow snow to accelerate once set in motion, additionally convex slopes are less stable than concave slopes, because of the disparity between the tensile strength of snow layers and their compressive strength. The composition and structure of the ground surface beneath the snowpack influences the stability of the snowpack, either being a source of strength or weakness. Avalanches are unlikely to form in very thick forests, but boulders and sparsely distributed vegetation can create weak areas deep within the snowpack through the formation of strong temperature gradients. Full-depth avalanches (avalanches that sweep a slope virtually clean of snow cover) are more common on slopes with smooth ground, such as grass or rock slabs.

Generally speaking, avalanches follow drainages down-slope, frequently sharing drainage features with summertime watersheds. At and below tree line, avalanche paths through drainages are well defined by vegetation boundaries called trim lines, which occur where avalanches have removed trees and prevented regrowth of large vegetation. Engineered drainages, such as the avalanche dam on Mount Stephen in Kicking Horse Pass, have been constructed to protect people and property by redirecting the flow of avalanches. Deep debris deposits from avalanches will collect in catchments at the terminus of a run out, such as gullies and river beds.

Slopes flatter than 25 degrees or steeper than 60 degrees typically have a lower incidence of avalanches. Human-triggered avalanches have the greatest incidence when the snow's angle of repose is between 35 and 45 degrees; the critical angle, the angle at which human-triggered avalanches are most frequent, is 38 degrees. When the incidence of human triggered avalanches is normalized by the rates of recreational use, however, hazard increases uniformly with slope angle, and no significant difference in hazard for a given exposure direction can be found. The rule of thumb is: A slope that is flat enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle.

The snowpack is composed of ground-parallel layers that accumulate over the winter. Each layer contains ice grains that are representative of the distinct meteorological conditions during which the snow formed and was deposited. Once deposited, a snow layer continues to evolve under the influence of the meteorological conditions that prevail after deposition.

For an avalanche to occur, it is necessary that a snowpack have a weak layer (or instability) below a slab of cohesive snow. In practice the formal mechanical and structural factors related to snowpack instability are not directly observable outside of laboratories, thus the more easily observed properties of the snow layers (e.g. penetration resistance, grain size, grain type, temperature) are used as index measurements of the mechanical properties of the snow (e.g. tensile strength, friction coefficients, shear strength, and ductile strength). This results in two principal sources of uncertainty in determining snowpack stability based on snow structure: First, both the factors influencing snow stability and the specific characteristics of the snowpack vary widely within small areas and time scales, resulting in significant difficulty extrapolating point observations of snow layers across different scales of space and time. Second, the relationship between readily observable snowpack characteristics and the snowpack's critical mechanical properties has not been completely developed.

While the deterministic relationship between snowpack characteristics and snowpack stability is still a matter of ongoing scientific study, there is a growing empirical understanding of the snow composition and deposition characteristics that influence the likelihood of an avalanche. Observation and experience has shown that newly fallen snow requires time to bond with the snow layers beneath it, especially if the new snow falls during very cold and dry conditions. If ambient air temperatures are cold enough, shallow snow above or around boulders, plants, and other discontinuities in the slope, weakens from rapid crystal growth that occurs in the presence of a critical temperature gradient. Large, angular snow crystals are indicators of weak snow, because such crystals have fewer bonds per unit volume than small, rounded crystals that pack tightly together. Consolidated snow is less likely to slough than loose powdery layers or wet isothermal snow; however, consolidated snow is a necessary condition for the occurrence of slab avalanches, and persistent instabilities within the snowpack can hide below well-consolidated surface layers. Uncertainty associated with the empirical understanding of the factors influencing snow stability leads most professional avalanche workers to recommend conservative use of avalanche terrain relative to current snowpack instability.

After digging a snow pit, it is possible to evaluate the snowpack for unstable layers. In this picture, snow from a weak layer has been easily scraped away by hand, leaving a horizontal line in the wall of the pit.

Avalanches only occur in a standing snowpack. Typically winter seasons at high latitudes, high altitudes, or both have weather that is sufficiently unsettled and cold enough for precipitated snow to accumulate into a seasonal snowpack. Continentality, through its potentiating influence on the meteorological extremes experienced by snowpacks, is an important factor in the evolution of instabilities, and consequential occurrence of avalanches faster stabilization of the snowpack after storm cycles. The evolution of the snowpack is critically sensitive to small variations within the narrow range of meteorological conditions that allow for the accumulation of snow into a snowpack. Among the critical factors controlling snowpack evolution are: heating by the sun, radiational cooling, vertical temperature gradients in standing snow, snowfall amounts, and snow types. Generally, mild winter weather will promote the settlement and stabilization of the snowpack; conversely, very cold, windy, or hot weather will weaken the snowpack.

At temperatures close to the freezing point of water, or during times of moderate solar radiation, a gentle freeze-thaw cycle will take place. The melting and refreezing of water in the snow strengthens the snowpack during the freezing phase and weakens it during the thawing phase. A rapid rise in temperature, to a point significantly above the freezing point of water, may cause avalanche formation at any time of year.

Persistent cold temperatures can either prevent new snow from stabilizing or destabilize the existing snowpack. Cold air temperatures on the snow surface produce a temperature gradient in the snow, because the ground temperature at the base of the snowpack is usually around 0 °C, and the ambient air temperature can be much colder. When a temperature gradient greater than 10 °C change per vertical meter of snow is sustained for more than a day, angular crystals called depth hoar or facets begin forming in the snowpack because of rapid moisture transport along the temperature gradient. These angular crystals, which bond poorly to one another and the surrounding snow, often become a persistent weakness in the snowpack. When a slab lying on top of a persistent weakness is loaded by a force greater than the strength of the slab and persistent weak layer, the persistent weak layer can fail and generate an avalanche.

Any wind stronger than a light breeze can contribute to a rapid accumulation of snow on sheltered slopes downwind. Wind slabs form quickly and, if present, weaker snow below the slab may not have time to adjust to the new load. Even on a clear day, wind can quickly load a slope with snow by blowing snow from one place to another. Top-loading occurs when wind deposits snow from the top of a slope; cross-loading occurs when wind deposits snow parallel to the slope. When a wind blows over the top of a mountain, the leeward, or downwind, side of the mountain experiences top-loading, from the top to the bottom of that lee slope. When the wind blows across a ridge that leads up the mountain, the leeward side of the ridge is subject to cross-loading. Cross-loaded wind-slabs are usually difficult to identify visually.

Snowstorms and rainstorms are important contributors to avalanche danger. Heavy snowfall will cause instability in the existing snowpack, both because of the additional weight and because the new snow has insufficient time to bond to underlying snow layers. Rain has a similar effect. In the short-term, rain causes instability because, like a heavy snowfall, it imposes an additional load on the snowpack; and, once rainwater seeps down through the snow, it acts as a lubricant, reducing the natural friction between snow layers that holds the snowpack together. Most avalanches happen during or soon after a storm.

Daytime exposure to sunlight will rapidly destabilize the upper layers of the snowpack if the sunlight is strong enough to melt the snow, thereby reducing its hardness. During clear nights, the snowpack can re-freeze when ambient air temperatures fall below freezing, through the process of long-wave radiative cooling, or both. Radiative heat loss occurs when the night air is significantly cooler than the snowpack, and the heat stored in the snow is re-radiated into the atmosphere.

When a slab avalanche forms, the slab disintegrates into increasingly smaller fragments as the snow travels downhill. If the fragments become small enough the outer layer of the avalanche, called a saltation layer, takes on the characteristics of a fluid. When sufficiently fine particles are present they can become airborne and, given a sufficient quantity of airborne snow, this portion of the avalanche can become separated from the bulk of the avalanche and travel a greater distance as a powder snow avalanche. Scientific studies using radar, following the 1999 Galtür avalanche disaster, confirmed the hypothesis that a saltation layer forms between the surface and the airborne components of an avalanche, which can also separate from the bulk of the avalanche.

Driving an avalanche is the component of the avalanche's weight parallel to the slope; as the avalanche progresses any unstable snow in its path will tend to become incorporated, so increasing the overall weight. This force will increase as the steepness of the slope increases, and diminish as the slope flattens. Resisting this are a number of components that are thought to interact with each other: the friction between the avalanche and the surface beneath; friction between the air and snow within the fluid; fluid-dynamic drag at the leading edge of the avalanche; shear resistance between the avalanche and the air through which it is passing, and shear resistance between the fragments within the avalanche itself. An avalanche will continue to accelerate until the resistance exceeds the forward force.

Attempts to model avalanche behaviour date from the early 20th century, notably the work of Professor Lagotala in preparation for the 1924 Winter Olympics in Chamonix. His method was developed by A. Voellmy and popularised following the publication in 1955 of his Ueber die Zerstoerungskraft von Lawinen (On the Destructive Force of Avalanches).

Voellmy used a simple empirical formula, treating an avalanche as a sliding block of snow moving with a drag force that was proportional to the square of the speed of its flow:

He and others subsequently derived other formulae that take other factors into account, with the Voellmy-Salm-Gubler and the Perla-Cheng-McClung models becoming most widely used as simple tools to model flowing (as opposed to powder snow) avalanches.

Since the 1990s many more sophisticated models have been developed. In Europe much of the recent work was carried out as part of the SATSIE (Avalanche Studies and Model Validation in Europe) research project supported by the European Commission which produced the leading-edge MN2L model, now in use with the Service Restauration des Terrains en Montagne (Mountain Rescue Service) in France, and D2FRAM (Dynamical Two-Flow-Regime Avalanche Model), which was still undergoing validation as of 2007. Other known models are the SAMOS-AT avalanche simulation software and the RAMMS software.

Preventative measures are employed in areas where avalanches pose a significant threat to people, such as ski resorts, mountain towns, roads, and railways. There are several ways to prevent avalanches and lessen their power and develop preventative measures to reduce the likelihood and size of avalanches by disrupting the structure of the snowpack, while passive measures reinforce and stabilize the snowpack in situ. The simplest active measure is repeatedly traveling on a snowpack as snow accumulates; this can be by means of boot-packing, ski-cutting, or machine grooming. Explosives are used extensively to prevent avalanches, by triggering smaller avalanches that break down instabilities in the snowpack, and removing overburden that can result in larger avalanches. Explosive charges are delivered by a number of methods including hand-tossed charges, helicopter-dropped bombs, Gazex concussion lines, and ballistic projectiles launched by air cannons and artillery. Passive preventive systems such as snow fences and light walls can be used to direct the placement of snow. Snow builds up around the fence, especially the side that faces the prevailing winds. Downwind of the fence, snow build-up is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees, they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in the building of a ski resort, to reduce the strength of avalanches.

In turn, socio-environmental changes can influence the occurrence of damaging avalanches: some studies linking changes in land-use/land-cover patterns and the evolution of snow avalanche damage in mid latitude mountains show the importance of the role played by vegetation cover, that is at the root of the increase of damage when the protective forest is deforested (because of demographic growth, intensive grazing and industrial or legal causes), and at the root of the decrease of damage because of the transformation of a traditional land-management system based on overexploitation into a system based on land marginalization and reforestation, something that has happened mainly since the mid-20th century in mountain environments of developed countries

In many areas, regular avalanche tracks can be identified and precautions can be taken to minimize damage, such as the prevention of development in these areas. To mitigate the effect of avalanches the construction of artificial barriers can be very effective in reducing avalanche damage. There are several types: One kind of barrier ( snow net) uses a net strung between poles that are anchored by guy wires in addition to their foundations. These barriers are similar to those used for rockslides. Another type of barrier is a rigid fence-like structure ( snow fence) and may be constructed of steel, wood or pre-stressed concrete. They usually have gaps between the beams and are built perpendicular to the slope, with reinforcing beams on the downhill side. Rigid barriers are often considered unsightly, especially when many rows must be built. They are also expensive and vulnerable to damage from falling rocks in the warmer months. In addition to industrially manufactured barriers, landscaped barriers, called avalanche dams stop or deflect avalanches with their weight and strength. These barriers are made out of concrete, rocks, or earth. They are usually placed right above the structure, road, or railway that they are trying to protect, although they can also be used to channel avalanches into other barriers. Occasionally, earth mounds are placed in the avalanche's path to slow it down. Finally, along transportation corridors, large shelters, called snow sheds, can be built directly in the slide path of an avalanche to protect traffic from avalanches.

Warning systems can detect avalanches which develop slowly, such as ice avalanches caused by icefalls from glaciers. Interferometric radars, high-resolution cameras, or motion sensors can monitor instable areas over a long term, lasting from days to years. Experts interpret the recorded data and are able to recognize upcoming ruptures in order to initiate appropriate measures. Such systems (e.g. the monitoring of the Weissmies glacier in Switzerland) can recognize events several days in advance.

Radar station for avalanche monitoring in Zermatt.[28]

Modern radar technology enables the monitoring of large areas and the localization of avalanches at any weather condition, by day and by night. Complex alarm systems are able to detect avalanches within a short time in order to close (e.g. roads and rails) or evacuate (e.g. construction sites) endangered areas. An example of such a system is installed on the only access road of Zermatt in Switzerland. Two radars monitor the slope of a mountain above the road. The system automatically closes the road by activating several barriers and traffic lights within seconds such that no people are harmed.

Survival, rescue, and recovery

Avalanche accidents are broadly differentiated into 2 categories: accidents in recreational settings, and accidents in residential, industrial, and transportation settings. This distinction is motivated by the observed difference in the causes of avalanche accidents in the two settings. In the recreational setting most accidents are caused by the people involved in the avalanche. In a 1996 study, Jamieson et al. (pages 7-20) found that 83% of all avalanches in the recreational setting were caused by those who were involved in the accident. In contrast, all of the accidents in the residential, industrial, and transportation settings were due to spontaneous natural avalanches. Because of the difference in the causes of avalanche accidents, and the activities pursued in the two settings, avalanche and disaster management professionals have developed two related preparedness, rescue, and recovery strategies for each of the settings.

Two avalanches occurred in March 1910 in the Cascade and Selkirk Mountain ranges; on 1 March the Wellington avalanche killed 96 in Washington state, United States. Three days later 62 railroad workers were killed in the Rogers Pass avalanche in British Columbia, Canada.

During World War I, an estimated 40,000 to 80,000 soldiers died as a result of avalanches during the mountain campaign in the Alps at the Austrian-Italian front, many of which were caused by artillery fire. Some 10,000 men, from both sides, died in avalanches in December 1916.

In the northern hemisphere winter of 1950-1951 approximately 649 avalanches were recorded in a three-month period throughout the Alps in Austria, France, Switzerland, Italy and Germany. This series of avalanches killed around 265 people and was termed the Winter of Terror.

In 1993, the Bayburt Üzengili avalanche killed 60 individuals in Üzengili in the province of Bayburt, Turkey.

A large avalanche in Montroc, France, in 1999, 300,000 cubic metres of snow slid on a 30° slope, achieving a speed in the region of 100 km/h (62 mph). It killed 12 people in their chalets under 100,000 tons of snow, 5 meters (16 feet) deep. The mayor of Chamonix was convicted of second-degree murder for not evacuating the area, but received a suspended sentence.

The small Austrian village of Galtür was hit by the Galtür avalanche in 1999. The village was thought to be in a safe zone but the avalanche was exceptionally large and flowed into the village. Thirty-one people died.

On 1 December 2000, the Glory Bowl Avalanche formed on Mt. Glory which is located within the Teton Mountain Range in Wyoming, United States. Joel Roof was snowboarding recreationally in this backcountry, bowl-shaped run and triggered the avalanche. He was carried nearly 2,000 feet to the base of the mountain and was not successfully rescued.

On 3 July 2022 a serac collapsed on the Marmolada Glacier, Italy, causing an avalanche that killed 11 alpinists and injured 8.

In Europe, the avalanche risk is widely rated on the following scale, which was adopted in April 1993 to replace the earlier non-standard national schemes. Descriptions were last updated in May 2003 to enhance uniformity.

In France, most avalanche deaths occur at risk levels 3 and 4. In Switzerland most occur at levels 2 and 3. It is thought that this may be due to national differences of interpretation when assessing the risks.

[1] Stability:

Generally described in more detail in the avalanche bulletin (regarding the altitude, aspect, type of terrain etc.)

[2] additional load:

heavy: two or more skiers or boarders without spacing between them, a single hiker or climber, a grooming machine, avalanche blasting

light: a single skier or snowboarder smoothly linking turns and without falling, a group of skiers or snowboarders with a minimum 10 m gap between each person, a single person on snowshoes

Gradient:

gentle slopes: with an incline below about 30°

steep slopes: with an incline over 30°

very steep slopes: with an incline over 35°

extremely steep slopes: extreme in terms of the incline (over 40°), the terrain profile, proximity of the ridge, smoothness of underlying ground

In the United States and Canada, the following avalanche danger scale is used. Descriptors vary depending on country.

Danger Scale - English

Storm slab

Wind slab

Wet slab avalanches

Persistent slab

Deep persistent slab

Loose dry avalanches

Loose wet avalanches

Glide avalanches

Cornice fall

The Canadian classification for avalanche size is based upon the consequences of the avalanche. Half sizes are commonly used.

Size

Destructive Potential

1

Relatively harmless to people.

2

Could bury, injure or kill a person.

3

Could bury and destroy a car, damage a truck, destroy a small building or break a few trees.

4

Could destroy a railway car, large truck, several buildings or a forest area up to 4 hectares.

5

Largest snow avalanche known. Could destroy a village or a forest of 40 hectares.

The size of avalanches are classified using two scales; size relative to destructive force or D-scale and size relative to the avalanche path or R-scale. Both size scales range from 1 to 5 with the D size scale half sizes can be used.

Size Relative to Path

R1~Very small, relative to the path.

R2~Small, relative to the path

R3~Medium, relative to the path

R4~Large, relative to the path

R5~Major or maximum, relative to the path

Slab avalanche hazard analysis can be done using the Rutschblock Test. A 2 m wide block of snow is isolated from the rest of the slope and progressively loaded. The result is a rating of slope stability on a seven step scale. ( Rutsch means slide in German).

Avalanche formation and frequency is highly affected by weather patterns and the local climate. Snowpack layers will form differently depending on whether snow is falling in very cold or very warm conditions, and very dry or very humid conditions. Thus, climate change may affect when, where, and how often avalanches occur, and may also change the type of avalanches that are occurring.

Overall, a rising seasonal snow line and a decrease in the number of days with snow cover are predicted. Climate change-caused temperature increases and changes in precipitation patterns will likely differ between the different mountain regions, and the impacts of these changes on avalanches will change at different elevations. In the long term, avalanche frequency at lower elevations is expected to decline corresponding to a decrease in snow cover and depth, and a short-term increase in the number of wet avalanches are predicted.

Precipitation is expected to increase, meaning more snow or rain depending on the elevation. Higher elevations predicted to remain above the seasonal snow line will likely see an increase in avalanche activity due to the increases in precipitation during the winter season. Storm precipitation intensity is also expected to increase, which is likely to lead to more days with enough snowfall to cause the snowpack to become unstable. Moderate and high elevations may see an increase in volatile swings from one weather extreme to the other. Predictions also show an increase in the number of rain on snow events, and wet avalanche cycles occurring earlier in the spring during the remainder of this century.

McClung, David. Snow Avalanches as a Non-critical, Punctuated Equilibrium System: Chapter 24 in Nonlinear Dynamics in Geosciences, A.A. Tsonsis and J.B. Elsner (Eds.), Springer, 2007[ISBN missing ]

Daffern, Tony: Avalanche Safety for Skiers, Climbers and Snowboarders, Rocky Mountain Books, 1999, ISBN 0-921102-72-0

Billman, John: Mike Elggren on Surviving an Avalanche. magazine February 2007: 26.

McClung, David and Shaerer, Peter: The Avalanche Handbook, The Mountaineers: 2006. ISBN 978-0-89886-809-8

Tremper, Bruce: Staying Alive in Avalanche Terrain, The Mountaineers: 2001. ISBN 0-89886-834-3

Munter, Werner: Drei mal drei (3x3) Lawinen. Risikomanagement im Wintersport, Bergverlag Rother, 2002. ISBN 3-7633-2060-1 (in German) (partial English translation included in PowderGuide: Managing Avalanche Risk ISBN 0-9724827-3-3)

Michael Falser: Historische Lawinenschutzlandschaften: eine Aufgabe für die Kulturlandschafts- und Denkmalpflege In: kunsttexte 3/2010, unter: Historische Lawinenschutzlandschaften: eine Aufgabe für die Kulturlandschafts- und Denkmalpflege

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An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earthquakes.

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Snow Blindness: How to Prevent Sunburned Eyes

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Snow blindness is a painful, temporary loss of vision due to a sunburned eye. Learn how to avoid becoming snowblind.

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This guy gave himself hypothermia

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How to administer first aid for hypothermia.