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Definition:
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A restricted space, the length of which is comparable with the width of ice-free water, or very open broken ice among solid, very close and close ice. Diamond- or lens-shaped fractures form as a result of the shear of ice floes along the line of an earlier crack or lead. Due to cracks and leads not being rectilinear, they expand in some places and converge in other places under slight pressure. Hummocking can form a chain of fractures. This is the most stable type of fracture and can exist for several months. In the autumn-winter period, nilas and young ice and then first-year ice forms at their surface. Less stable fractures the shape and dimensions of which constantly change, are formed as a result of shears between giant and vast ice floes and by local divergance of close ice of smaller formations.
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