In the high-altitude world of snow-covered peaks and glaciers, one of the most dangerous and fascinating natural features is the crevasse. For climbers, glaciologists, and adventure seekers, understanding what a crevasse is on a mountain can be the difference between a successful expedition and a life-threatening situation. These deep cracks in glacier ice are formed by natural forces, yet they pose real risks due to their hidden depths and sudden appearances. Exploring their origin, types, and significance helps shed light on why crevasses deserve respect and caution in mountainous terrain.
Definition of a Crevasse
What Exactly Is a Crevasse?
A crevasse is a deep, open crack that forms in a glacier or ice sheet as a result of stress. When glacial ice moves over uneven terrain or around obstacles such as rocks or ridges, the surface of the glacier is pulled apart. Since ice is rigid and cannot bend easily, this tension causes it to fracture, forming a crevasse. On a mountain, crevasses typically occur where glaciers are active and the ice flow is under pressure due to gravity and slope changes.
Crevasses vs. Cracks
It’s important not to confuse a crevasse with a simple surface crack. Crevasses can be several meters wide and extend tens of meters deep sometimes even reaching all the way to the bottom of the glacier. While cracks may appear on dry rock surfaces due to weathering or seismic activity, crevasses are unique to glacial environments.
Formation of Crevasses on Mountains
Glacial Movement and Tension
Glaciers are rivers of ice that move slowly over time due to the force of gravity. As the ice flows downhill, the movement is not uniform. The top layers of ice move faster than the lower layers that are in contact with the rocky bed below. This uneven motion creates tension in the upper layers, especially where the glacier changes direction, speed, or slope. When the stress exceeds the ice’s ability to deform smoothly, it cracks, forming a crevasse.
Influence of Terrain
Mountainous terrain contributes heavily to crevasse formation. As glaciers flow over convex slopes or sharp changes in elevation, they are pulled apart at the surface. This effect is more pronounced in steep mountain regions, where crevasses often form in clusters or in predictable zones such as icefalls or glacier tongues.
Types of Crevasses
Crevasses come in various forms depending on the stress patterns and flow direction of the glacier. Recognizing these types is crucial for understanding glacier behavior and for safe mountaineering.
- Transverse CrevasseThese crevasses run perpendicular to the glacier flow. They typically form when the glacier speeds up as it moves downhill.
- Longitudinal CrevasseThese run parallel to the glacier’s flow and occur when the glacier spreads outward or turns around obstacles.
- Chevron CrevasseThese V-shaped crevasses appear where the glacier is bending or changing direction. They often occur in complex terrain.
- BergschrundFound near the top of a glacier where it separates from the rock face, bergschrunds mark the beginning of glacial flow. They can be extremely deep and dangerous.
Danger and Hazards of Crevasses
Hidden Dangers
Crevasses are among the most hazardous features for mountaineers and glacier hikers. One major risk is that crevasses may be hidden beneath a thin layer of snow, known as a snow bridge. These snow bridges may appear solid but can collapse under a person’s weight, leading to falls into deep ice chasms.
Injury and Rescue Challenges
Falling into a crevasse can result in serious injury or death due to impact, exposure to cold, or inability to climb out. Rescuing someone from a crevasse is highly technical and often requires ropes, pulleys, and a trained team. In extreme conditions, rescue efforts can be delayed or become impossible due to weather or unstable terrain.
Navigation and Safety Measures
Traveling on Glaciers Safely
To minimize the risk of falling into a crevasse on a mountain, climbers use specific safety strategies
- Roped TravelClimbers traveling in teams rope themselves together. If one person falls into a crevasse, the others can arrest the fall and assist in a rescue.
- Probing and ObservationUsing poles or ice axes, climbers can test the firmness of the snow ahead to detect hidden crevasses.
- Route PlanningGuides often select paths that avoid known crevasse zones. Early morning travel is also preferred when the snow bridges are more solid due to lower temperatures.
Training and Equipment
Climbers operating in glacial environments are trained in crevasse rescue techniques. Essential gear includes harnesses, carabiners, ice screws, ascenders, and pulleys. Understanding how to build an anchor and perform a Z-pulley rescue system is fundamental for any team navigating crevassed terrain.
Scientific Importance of Crevasses
Clues to Glacier Behavior
Crevasses are more than just hazards they are indicators of a glacier’s dynamics. Scientists study crevasse patterns to determine stress zones, flow direction, and the health of a glacier. As climate change alters global temperatures, glaciers are retreating, thinning, or flowing more rapidly, and crevasse behavior can offer insight into these changes.
Monitoring Climate Effects
By analyzing crevasse formation and frequency, researchers can assess the stability of a glacier and predict potential ice collapse. In mountainous areas such as the Himalayas, Alps, or Andes, this data is critical for assessing flood risks from glacial lakes or anticipating landslides caused by melting permafrost.
Crevasses in Popular Mountain Ranges
Notable Regions with Crevassed Glaciers
Some of the world’s most iconic mountains have glaciers riddled with crevasses. For instance
- Mount Everest RegionThe Khumbu Icefall is infamous for its labyrinth of shifting ice blocks and deep crevasses.
- AlpsThe Mer de Glace near Mont Blanc contains large crevasses and is a popular site for guided glacier tours and mountaineering.
- AlaskaGlaciers on Denali, the highest peak in North America, feature extensive crevassed zones that challenge climbers daily.
Crevasses are powerful reminders of the natural forces at work in high mountain environments. Formed by the movement and stress within glaciers, these deep ice fissures represent both a geological phenomenon and a significant danger for adventurers. Understanding what a crevasse is on a mountain involves more than just identifying a crack in the ice it means grasping the mechanics of glacial flow, recognizing terrain risks, and applying knowledge to ensure safety. For scientists, they are valuable tools for studying climate change and glacier dynamics. For climbers, they are features that demand respect, preparation, and vigilance. As mountain glaciers continue to shift in a warming world, the role and presence of crevasses will remain a vital part of understanding alpine landscapes.