Bivouac

In the mountaineering context, a bivouac or "biv(v)y" is a makeshift resting or sleeping arrangement in which the climber has less than the full complement of shelter, food and equipment that would normally be present at a conventional campsite. This may involve simply getting a sleeping bag and Bivouac sack/bivvy bag and lying down to sleep. Typically bivvy bags are made from breathable waterproof membranes, which move moisture away from the climber into the outside environment while preventing outside moisture from entering the bag. Many times small partially sheltered areas such as a bergschrund, cracks in rocks or a trench dug in the snow are used to provide additional shelter from wind. These techniques were originally used only in emergency; however some climbers steadfastly committed to alpine style climbing specifically plan for bivouacs in order to save the weight of a tent when suitable snow conditions or time is unavailable for construction of a snow cave. The principal hazard associated with bivouacs is the greater level of exposure to cold and other elements present in harsh conditions high on the mountain.