Glacier Travel Crevasse Rescue I: Hazards of glaciated terrain

Objective Hazards and Decision Making in the Karakoram and Lesser Himalayas – taking responsibility for your own safety
August 24, 2016
Planning your first Himalayan Expedition to Pakistan
April 5, 2017
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Glacier Travel Crevasse Rescue I: Hazards of glaciated terrain



After I wrote the ‘Objective hazards and decision making’ blog, I received several queries on traveling in glaciated terrain. This is one of four blogs I will write on glacier travel crevasse rescue. There is no substitute for learning these techniques from an AMGA/IFMGA certified guide. The guidelines I provide here must be used with the publication list I provided in my last blog.

Glaciers form in the poles (ice caps) and in mountain ranges (alpine/valley glaciers). Their movement is a function of the rate of snow accumulation versus the rate at which snow melts. The focus of this website is the Himalayas therefore these blogs will cover alpine glaciers.

In the Karakoram, the snow line (elevation above which snow remains all year round) is around 15,000 feet (4500 meters). After a snowfall, snowflakes begin to interlock. Wind can facet the snow into crystals. Freeze-thaw cycles repeat and in about a year that snow turns into firn. As more snow accumulates on top, pressure and time will create ice crystals. This is the genesis of glacial ice. Under the influence of gravity this ice begins to slide downhill. In the Karakoram, a large number of glaciers are formed by repeated avalanche activity. Avalanche debris above the snow line will go through the same process mentioned above and will begin to move en masse. The moving ice will erode along its base and edges. Eroded material will sometimes be entrained in the ice itself. Like a giant bulldozer the glacier will pile a mixture of clay and silt with rocks of all shapes and sizes (till) along its front and its sides. These piles of till are called moraines. When two or more glaciers meet, these moraines along the edges (lateral moraines) will merge to form medial moraines. A final accumulation of till will accumulate at the frontal edge or terminus of the glacier. As the glacier flows below the snowline, it begins to melt.



The snowline is clearly visible here in the peaks of Central Karakoram, Hunza Valley.


For someone traveling on a glacier it is imperative to understand the difference between this zone of melting (also known as the ablation zone) and the zone of accumulation. The zone of accumulation is visibly white, because it lacks a cover of rock debris. It is often snow-covered even during the summer. The ablation zone appears to be ‘dirty’, often in shades of grey or brown depending on the color of rocks that rest on top. This zone also contains streams that pour into holes called moulins. The mouth or snout of the glacier is where all the melt water flows out as an outwash stream.

Each zone has its own hazards, and if you are to travel on the glacier you must learn to identify these, such that they can be avoided. As the glacier curves or moves over convexities in the landscape it begins to break. Large fractures in the ice are called crevasses. These can be a few feet to over a hundred feel in depth. Crevasses can sometimes isolate large chunks of ice called seracs. Seracs are inherently dangerous as they can collapse under their own weight. If the glacier flows down a steep slope, then it shatters into a labyrinth of crevasse-bound seracs and is called an ice fall. The majority of accidents on glaciers involve crevasses.

In the ablation zone, crevasses are clearly visible, and can be easily avoided – assuming you are traveling in summer when there is little or no snow covering the glacier. Because crevasses are visible, there is no need to be roped up. Another reason to not be tied-up in the ablation zone is because if one member of a roped team falls into a crevasse, others cannot go into self-arrest, which means that others will get pulled into the crevasse as well. The lack of snow limits the ability to create and anchor or any sort of hauling system. Therefore, roping up on this part of the glacier is generally a bad idea.

The ablation (debris covered) and accumulation (bare ice) zones are clearly visible on the Bualtar Glacier

The ablation (debris covered) and accumulation (bare ice) zones are clearly visible on the Bualtar Glacier

While traveling on to the glacier, one must not stand underneath steep walls of the lateral or terminal moraine. Large rocks that are suspended in clay can be dislodged at any time and can cause serious injury. If you are approaching the glacier from its edge, then you will probably run into a deep trench that separates the ice from the lateral moraine. This is known as a moat and can be several hundreds of feet deep and filled with ice-cold water. This is a pretty obvious hazard, and no one deliberately approaches a moat. However these moats are often hidden by overhanging terminal moraines. An example of this is “lookout point” when approaching the Raikot Face basecamp of Nanga Parbat. Local “guides” will often recommend that you hike to lookout point from Beyal camp to avoid the long hike to base-camp. Look out point is on the lateral moraine of the Raikot Glacier, the edge of which is overhanging. A slip here while trying to take pictures can result in a serious fall. A similar hazard occurs on the Karakoram highway itself at Tatta Pani near Chilas. Moraines let behind by glaciers of the last ice-age form large cliffs along the roadside. During monsoons boulders the size of cars are dislodged and come tumbling down. You can see the result in this photo where several electric poles are bent and broken.

Ice-fall near Rakaposhi base-camp. All the large pieces of ice are seracs and are separated by crevasses

Ice-fall near Rakaposhi base-camp. All the large pieces of ice are seracs and are separated by crevasses

While on a glacier, once you enter the zone of accumulation, crevasses are covered with snow. Therefore you must rope-up. Being attached to a rope in itself does nothing. Your team must know the correct number of people to put on a rope, the spacing between each person, the tension in the rope, and how to build hauling systems to get someone out of a crevasse. It also requires specialized gear and the ability to use it correctly. These are topics I will be covering in the next blog. To summarize:

  1. Learn to differentiate the ablation from the accumulation zone.
  2. Do not rope up in the ablation zone, roping up can actually increase the risk of an accident
  3. Do not wander close to the edge of a glacier, especially if there is moat
  4. Do not stand underneath moraine cliffs to take pictures – always be aware of what can fall on you, especially after a rainfall
  5. Before you wander onto the ablation zone, your gear must be ready and rigged, you should be in a roped party where everyone knows how to rescue themselves and others.


  1. ig says:

    I wanted to thank you for this wonderful read!!
    I absolutely enjoyed every little bit of it. I’ve got you bookmarked to check out new stuff you post…

  2. Yacon Root says:

    Great Website. Very much enjoyed reading.

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