Crevasses are dramatic and often dangerous features that appear in glacier ice. These deep, narrow cracks form as a result of the movement and stress within the glacier, particularly when it flows over uneven terrain. For scientists, explorers, and mountaineers, understanding crevasse depth is essential not only for safety but also for gaining insights into glacier dynamics. The depth of a crevasse is influenced by various factors including ice thickness, internal stresses, and the glacier’s velocity. While some crevasses may seem shallow on the surface, others plunge to startling depths.
What Is a Crevasse?
Definition and Formation
A crevasse is a deep fracture or crack that forms in glacier ice due to the stress of movement. As glaciers slowly flow downhill or across uneven ground, the ice experiences tension and compression. When the tensile stress exceeds the ice’s ability to deform plastically, it breaks, resulting in a crevasse.
Types of Crevasses
There are several types of crevasses, each associated with different stress conditions
- Transverse crevassesForm perpendicular to the glacier’s flow, typically where the glacier is accelerating.
- Longitudinal crevassesRun parallel to the flow and appear when the glacier spreads out laterally.
- Chevron crevassesOccur in a V-pattern, usually where the glacier is bending around obstacles.
- Marginal crevassesAppear near the edges of glaciers, caused by shear stress between the glacier and valley walls.
Average and Maximum Crevasse Depths
Typical Depth Range
Most crevasses range from 10 to 30 meters (approximately 30 to 100 feet) deep. In areas where ice is less thick or where internal stress is moderate, crevasses tend to be narrower and shallower. These depths are still enough to pose a serious risk to climbers or skiers crossing glaciers.
Maximum Recorded Depths
Under extreme stress and in thicker glaciers, crevasses can reach depths of up to 45 meters (about 150 feet), though some estimates and studies suggest that in rare conditions, they may extend even deeper up to 60 meters (200 feet) or more. However, crevasses rarely exceed one-third the total thickness of the glacier ice.
Factors Influencing Crevasse Depth
Ice Thickness
The thicker the glacier, the deeper a crevasse can potentially form. The glacier’s depth provides a vertical stress gradient, which plays a role in determining where fractures can propagate. In thick ice sheets such as those found in Greenland or Antarctica, deeper crevasses may form compared to alpine glaciers.
Temperature and Ice Behavior
Cold ice tends to be more brittle, making it more likely to fracture deeply. In contrast, warmer ice behaves more plastically and resists deep fracturing. This is why temperate glaciers may exhibit shallower crevasses despite similar stress conditions.
Glacier Speed and Stress
Faster-moving glaciers generate greater shear and tensile stresses. These increased stresses cause crevasses to open more quickly and potentially deepen. Conversely, slower or stagnant glaciers tend to have fewer or shallower crevasses.
Crevasse Hazards and Exploration
Risk for Mountaineers
Crevasses are one of the primary hazards for anyone traveling across glaciers. Snow often bridges the tops of crevasses, creating an illusion of solid ground. When weight is applied, these fragile snow bridges can collapse, leading to potentially fatal falls.
Safety Measures
Glacier travelers take various precautions to avoid or survive crevasse falls
- Traveling in roped teams
- Using harnesses and crevasse rescue gear
- Probing snow surfaces for hidden crevasses
- Training in crevasse rescue techniques
Scientific Use of Crevasses
While hazardous, crevasses also offer valuable opportunities for scientists. Researchers can lower instruments into crevasses to study internal ice temperatures, measure deformation, and collect climate data preserved in layers of glacier ice. In this way, deep crevasses become natural laboratories for glaciological research.
Crevasse Behavior in Different Regions
Alpine Glaciers
In mountain regions such as the Alps, Rockies, or Himalayas, glaciers are typically thinner and smaller. Crevasses here are often shallower, but still dangerous due to narrow terrain and steep slopes. In these environments, crevasses may range from 5 to 25 meters deep.
Polar Ice Sheets
In places like Antarctica or Greenland, crevasses can be much larger due to the vast thickness and movement of the ice. Some of the deepest known crevasses over 40 meters have been found in these polar regions, particularly near ice shelves or fast-moving outlet glaciers.
Tidewater Glaciers
Glaciers that terminate in the ocean, such as those in Alaska, often develop complex crevasse patterns near their edges. These areas are prone to calving events, and crevasses in such zones can open rapidly and unpredictably due to tidal forces and ice-ocean interactions.
Myths and Misconceptions
Bottomless Crevasses
One common myth is that crevasses are bottomless. In reality, every crevasse has a bottom, though it may be difficult to see or measure due to narrow walls and snow accumulation. Ice will begin to behave plastically under high pressure, preventing cracks from continuing indefinitely.
Crevasses Always Stay Open
Another misconception is that crevasses remain open permanently. In fact, glaciers are dynamic, and crevasses can close over time due to ice flow, snowfall, or melting. Seasonal changes may also cause snow to cover or fill old crevasses.
The depth of a crevasse varies greatly depending on environmental conditions, glacier thickness, and ice stress. While most crevasses fall within a range of 10 to 30 meters, deeper crevasses reaching up to 60 meters are possible in the right conditions. For anyone navigating glaciers, understanding how deep a crevasse can be is essential for ensuring safety and preparation. In addition to their danger, crevasses also provide unique insight into glacier mechanics and climate history. Whether viewed from a mountaineer’s or a scientist’s perspective, the vertical world of crevasses is as fascinating as it is formidable.