ice dam

1. An obstruction to the flow of a river caused by the flow of a glacier across its course.

2. An obstruction to the flow of a river caused by the concatenation of surface ice into a ridge that rises above and sinks below the surface causing a blockage, occurring frequently during spring breakup season.

3. A mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the overhang of a steep roof, causing ice and water to back up under roofing materials.

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