Beware of “White Dragons”!


What flies without wings, hits without hands, and sees without eyes?​—A riddle about white dragons told since the Middle Ages.

AVALANCHES, aptly named white dragons, can swallow a mountaineer or even entomb a whole village in just the blink of an eye. For that reason, people called avalanches the white death. What are these awe-inspiring phenomena? If you live among snowcapped mountains, you already know the answer. If, though, you call a tropical region your home or you are a lowlander, you may not be concerned, since avalanches will never threaten you unless you take a trip and venture into white dragon territory.

Avalanches are born in high mountains where snow falls freely and often. Their birth is announced suddenly when large masses of snow, ice, earth, rock, and other materials, such as tree trunks, cascade swiftly down a mountainside or over a precipice, often destroying everything in their path. Not only do the weight and power of an avalanche wreak havoc but the air pressure that precedes one can also lay low dense clusters of trees and damage other objects in its way, such as bridges, roads, or railway lines.

A Natural Phenomenon

For the most part, the mass of thundering tons of white power is made up of tiny snowflakes. How can something as beautiful as falling snow become so deadly as a roaring avalanche? The answer lies in the characteristics of snow. Snow comes in different shapes: crystals, pellets, and granules. The crystal flakes are always six-pointed stars in an endless variety of patterns. Each one is a marvel in itself. Once these crystals have fallen to the ground, they can change their appearance. Differences in air temperature and the pressure from accumulating snow cause them to become smaller as they settle. Within a period of merely 24 hours, a foot [30 cm] of fresh snow can compact to only four inches [10 cm].

Depending on the shape of the snowflakes, the stability of the snow cover will fluctuate. Six-pointed crystals interlock, but granules and pellets roll over each other and produce unstable layers. These can easily slide over a more solid layer underneath. So the kind of snow, the quantity that has fallen, the steepness of the terrain, temperature differences, and the force of winds all determine whether an avalanche will be set in motion. An avalanche can also unwittingly be triggered by the body weight of either a man or an animal passing over a steep snowfield. However, other kinds of avalanches exist.

Wind avalanches originate when a mixture of granular and crystalline fresh snow​—the kind of loose powder that skiers love—​is sent airborne by a strong gust of wind. Being light, the snow is lifted into the air and can swoop down the valley at more than 200 miles [300 km] an hour. In this case, air pressure ahead of the snow mass builds up to such an extent that the airborne avalanche can lift off roofs and even destroy houses in a matter of seconds.

 A most deadly kind of avalanche is the hard-slab avalanche. These slab avalanches are caused by a buildup of old snow that has settled and compressed over a period of time. When the top layer of snow breaks up, big chunks of ice may slide down a mountain slope at between 30 and 50 miles [50 and 80 km] an hour. Such hard deposits may also hang out over the edge of a cliff. These pose a great danger for skiers, as the weight of just one skier is sufficient to break off the slab and trigger an avalanche that may bury him in seconds.

In springtime the danger of avalanches increases. Either rain or bright sunshine makes the snow mushy, which often results in wet-slab avalanches. They move more slowly, but a whole slope may be involved. As the snow mass glides down, it picks up boulders, trees, and soil, which develop into dirty walls of debris at its terminal point.

A phenomenon similar to the avalanche is the glacier, or ice avalanche. Glaciers are huge slabs of ice that form in very cold regions​—in depressions or on shady slopes where the snow never melts. In the course of time, however, the snow freezes to solid ice. Glaciers move downward very slowly. Because their movement is predictable, they seldom cause much injury or damage.

Where Do Avalanches Occur?

Not all snowy regions on our planet produce avalanches. For them to occur, there must be mountains of a certain height and a climate that allows for snow and ice. Statistics indicate that worldwide about one million avalanches occur every year. Some danger zones exist in the Andes of South America, the Rocky Mountains of North America, the Himalayas in Asia and, of course, the Alps in Europe, which stretch from France  northeastward through Switzerland, Germany, and Austria. In the inhabited parts of these regions, an average of 200 human lives are lost each year as a result of avalanches. Of these, an average of 26 are in Switzerland.

Two exceptionally devastating avalanches have occurred in the Andes of Peru. In the year 1962, a half-mile [1 km]-long chunk of ice separated from the 180-foot [50 m]-thick icecap of 22,205-foot [6,768 m]-high Mount Huascarán. The four-million-ton chunk of ice was four times the size of New York’s Empire State Building! This mass traveled 11 miles [18 km] in 15 minutes. Seven villages were buried beneath the snow, and between 3,000 and 4,000 lives were lost under the debris, which was 45 feet [13 m] deep and covered an area one mile [2 km] wide. In 1970, a similar event occurred again on that mountain. However, this time an earthquake shook loose the icecap on a northern peak. The mountain itself collapsed. Thousands of tons of snow, rock, and ice moved 200 miles [300 km] an hour through a narrow gorge, scooping up boulders and houses along the way. It was estimated that 25,000 people died. What can be done to protect inhabitants of mountainous areas from such tragic occurrences?

Can Avalanches Be Prevented?

Some avalanches can be prevented. Others cannot. Weather-induced avalanches cannot be prevented; they are as normal as rainwater running off a roof. They are a natural consequence of the seasonal cycle. But experience has taught governmental authorities in areas where these avalanches occur to ban construction of houses in danger zones and protect traffic arteries by building tunnels or galleries. On the other hand, avalanches caused by imprudent people, such as daring skiers who ignore warnings and prohibitions, could be prevented.

In Switzerland, past experiences caused the government to take precautions. In 1931 a Swiss research commission was founded, and in 1936 the first team of courageous researchers took up scientific studies at a height of 8,835 feet [2,690 m] in the area of the Weissfluhjoch, above the town of Davos. Later, in 1942, the Swiss Federal Institute for Snow and Avalanche Research was founded. Several other modern observatories were established in different locations in the mountains. These institutions make it possible for changing weather conditions to be forecast, and they regularly broadcast warnings regarding the danger of avalanches on exposed slopes.

Nevertheless, unforeseen weather developments are still possible, and risks cannot be eliminated. Therefore, everyone living in a danger zone or spending a vacation or a weekend in mountainous terrain in winter must be conscious of his responsibility to avoid causing avalanches. Interestingly, tests in France indicated that the sound waves planes create do not provoke avalanches, nor do human voices, as was formerly believed.

Official Measures of Protection

Soon after people started to settle in mountainous regions, they recognized the danger of avalanches. In order to stop the snow from burying their homes, they planted so-called ban forests on the slopes above their settlements. In many cases this protection was effective, which is why until today ban forests are still cared for by the local authorities. They are the best natural defense against  avalanches. However, experience has shown that the forest must be dense and contain several hundred trees for every 2.5 acres [1 ha], as well as older and younger trees of different species.

In recent times engineers have made metal barriers anchored in concrete. These are placed in breakaway zones above the first fence of trees. They can be constructed up to 12 feet [4 m] in height, but it would be too expensive to place them on every slope. To protect buildings from being swept off their foundation, avalanche breakers are also made of huge mounds of rock and dirt and are set at the bottom of slopes. These piles can divert avalanches and keep them from rushing into villages and homes in valleys. Other types of breakers are V-shaped walls of dirt 6 feet [2 m] thick and 16 feet [5 m] high. The point of the V faces uphill, so it can split an avalanche in two and force the snow to deflect to either side. The legs of the V measure 300 or 400 feet [90 or 120 m] in length and can protect entire towns. However, when important main roads or railway lines in the valleys are threatened, the best protection​—and the costliest too—​is provided by tunnels or galleries made of wood, steel, and concrete.

Another way to prevent avalanches is to break up heavy masses of snow. The Canadian army, for example, patrols between towns each winter and shoots into the snow. In this way they guard the Trans-Canada Highway, breaking up snow before it can avalanche and cover the road. To a certain extent, this method is also used in Switzerland, where in an effort to prevent avalanches, explosives are shot or dropped from helicopters onto unstable slopes to dislodge snow.

Avalanche Rescue

Skiers and hikers are supposed to wait while slopes are being tested for safety. Never ignore posted warnings! Remember that even the most experienced professional skier can be buried in snow. If you are caught in an avalanche, don’t panic! Move as if you were swimming in the ocean, advise experts. This will help to keep you near the top of the slide. Or push one arm as high as possible overhead. This might alert rescuers to your position. Cover your mouth and nose with your other hand. Rescue statistics show that only half of avalanche victims survive after being trapped for more than 30 minutes. Nowadays, some skiers carry beacons, such as battery-operated transmitters. Since the white death is ever present in high altitudes, speedy efforts to rescue avalanche victims are necessary.

For centuries, the famous Saint Bernard dogs were raised by Augustinian monks in the Swiss Alps. These dogs had the strength and stamina to move through deep snow and to withstand freezing winds and cold weather. They had a good sense of orientation and were very sensitive to sound and motion undetectable by humans. They thus saved hundreds of lives, even though they did not carry a keg of brandy on their collar while on rescue missions, as many pictures have portrayed them! Today most rescue dogs are German shepherds, but some other breeds are also trained for this type of work. In addition, electronic aids are effective, and careful probing by rescue workers can save lives. They cannot, however, match the success of trained dogs.

As we have seen, “what flies without wings, hits without hands, and sees without eyes” is a phenomenon demonstrating the powerful forces active in nature. White dragons demand our respect.

[Blurb on page 19]

If you are caught in an avalanche, move as if you were swimming in the ocean

[Picture on page 18]

Saint Bernard dogs are often pictured with a brandy keg, although they did not really carry them on rescue missions

[Picture Credit Line on page 17]

AP Photo/Matt Hage