How does ice deform under long-lasting stress?

When ice is subjected to long-lasting stress, it undergoes a process known as plastic deformation or creep.12

Initially, ice responds to stress with elastic deformation, meaning it would return to its original shape if the stress were removed. However, when a shear stress is applied over a long period, the ice continues to deform plastically, resulting in a permanent alteration of its shape. This behavior is a form of elasticoviscous deformation, where the material yields continuously under a constant load.132

This plastic flow involves two primary mechanisms:
* Intracrystalline gliding: Layers within an ice crystal shear parallel to one another without breaking the continuity of the crystal lattice.1
* Recrystallization: Crystal boundaries change in size or shape based on the orientation of adjacent crystals and the stresses applied to them.1

The speed of this deformation is controlled by the movement of dislocations—defects or disorders within the crystal lattice. Because ice deforms through this continuous plastic flow under long-term stress, it does not possess a distinct yield point or ultimate strength in the same way brittle materials do.1