Self-arrest is the technique of stopping yourself from sliding down a snow slope after a slip or fall, using an ice axe to dig into the snow and halt your descent before you accelerate out of control. The single most important snow-travel safety skill in mountaineering, self-arrest must be performed quickly and instinctively, and must be practiced regularly because a real slide gives almost no time to think.
An ice axe is the fundamental mountaineering tool used for balance, security, and self-arrest on snow and ice slopes. Its parts include the head (with a pick and an adze), the shaft, and the spike at the bottom. A general mountaineering axe is straight and used like a cane for support and to stop a slide, while more curved, aggressive ice tools are made for steep ice climbing.
Crampons are metal traction devices fitted with sharp points (spikes) that attach to mountaineering boots to provide grip on snow and ice. They range from lightweight aluminum models for glacier walking to steel technical crampons for ice climbing, and use strap-on, hybrid, or step-in bindings that must match the boot. Crampons are essential gear for travel on firm snow and ice.
Glacier travel is the practice of moving safely across glaciers, where the primary hazard is falling into hidden crevasses concealed by snow bridges. The fundamental technique is traveling as a roped team, spaced out and connected by the rope, so that if one climber breaks through, the others can arrest the fall and perform a crevasse rescue. It requires a broad skill set — rope management, anchors, crevasse rescue, and route-finding — and is essential, high-consequence terrain.
Crevasse rescue is the set of techniques used to extract a climber who has fallen into a crevasse during glacier travel. The process broadly involves arresting the fall, building an anchor, securing the fallen climber, and then hauling them out using a mechanical-advantage pulley system (or having them ascend the rope). Because crevasse falls happen suddenly and are life-threatening, crevasse rescue is an essential, practiced skill for anyone traveling on glaciers.
A crevasse is a deep crack or fissure in a glacier, formed as the ice moves over uneven terrain and fractures. Crevasses can be tens of meters deep and are especially dangerous when hidden under a thin bridge of snow that conceals the gap. Falling into one is a primary hazard of glacier travel, which is why climbers rope together and carry rescue gear.
The death zone is the extreme high-altitude region, generally defined as above about 8,000 meters (26,000 feet), where the amount of available oxygen is too low to sustain human life for an extended period. In the death zone the body deteriorates rather than acclimatizes — judgment, healing, and digestion all fail — so climbers must ascend, summit, and descend as quickly as possible, usually using supplemental oxygen.
HACE (high-altitude cerebral edema) is the most severe form of altitude illness — a life-threatening swelling of the brain caused by fluid accumulation at high altitude. Often considered the end stage of acute mountain sickness, its defining signs are confusion, loss of coordination (ataxia), and altered consciousness. Like HAPE, the definitive treatment is immediate descent, and it can be fatal within hours.
HAPE (high-altitude pulmonary edema) is a severe, life-threatening form of altitude illness in which fluid accumulates in the lungs, impairing oxygen uptake. It typically develops above 2,500 m (8,000 ft) when ascent is too rapid, and its hallmark signs are breathlessness at rest, a cough (sometimes with frothy or pink sputum), and weakness. The definitive treatment is immediate descent.
Altitude sickness is a range of illnesses caused by ascending to high elevation faster than the body can adjust to the lower oxygen. It spans mild acute mountain sickness (AMS) to the life-threatening high-altitude pulmonary edema (HAPE) and cerebral edema (HACE). The cornerstone of prevention is gradual ascent — acclimatization.
