Crevasse

A crevasse is a deep crack that forms in a glacier or ice sheet. These cracks happen because of the way glaciers move and the pressure they feel. When two parts of a glacier move at different speeds, it creates stress. This stress can cause the ice to break, forming a crevasse.

Crevasses are important to understand because they tell us about how glaciers move and change over time. They can be very deep and dangerous, especially for people who travel on ice. Scientists study crevasses to learn more about climate change and how it affects glaciers around the world.

Crevasses are not to be confused with a crevice, which is a smaller crack in rock or soil. Also, the word "crevasse" can sometimes mean a levee breach, but in the context of ice, it always refers to these deep cracks in glaciers.

Description

Crevasses are deep cracks that form in glaciers. They often have walls that stand straight up, and these walls can melt to create special shapes like seracs, arches, and other icy structures. The size of a crevasse depends on how much liquid water is in the glacier. Some crevasses can be as deep as 45 metres (150 feet) and as wide as 20 metres (70 feet).

When water gets into a crevasse, it can make the crack go all the way through the glacier. This water connects the top of the glacier, where a lot of melting happens in the summer, to the bottom. This can help make the glacier move faster. Water flowing down from the top, called moulins, can also help speed up the glacier’s movement.

Types

• Longitudinal crevasses form parallel to the direction a glacier moves when the glacier widens. They develop in areas where the glacier is being pulled apart, such as where a valley opens up or turns. These crevasses usually curve downward and form an angle larger than 45° with the side of the glacier.
• Splaying crevasses appear along the edges of a glacier and result from the force of the glacier rubbing against its sides. They stretch out from the glacier’s edge and curve upward, making an angle smaller than 45° with the side of the glacier.
• Transverse crevasses are the most common type. They form where the glacier is being stretched lengthwise, creating tension across the glacier. These crevasses run across the glacier, cutting from one side to the other, and usually form where the valley gets steeper.

Dangers

Falling into a deep crack in a glacier, called a crevasse, can be very dangerous. Some of these cracks can be very deep, like those near Mount Everest, and can hurt someone badly. The cold can also make it hard to stay safe if someone falls in.

Sometimes, snow can cover a crevasse, making it hard to see. This can be risky for people walking on a glacier. Climbers can stay safer by staying connected with ropes and using special knots.