Which ice is milky or opaque due to slow thawing and trapped air?

• A. Clear ice
• B. Rotten ice
• C. Drift ice
• D. Pack ice

Answer: (B)

Milky or opaque ice signals trapped air in the ice that forms during partial thaw and refreezing, producing a weak, porous layer known as rotten ice. This appearance shows the ice isn’t a solid, uniform structure; the air pockets reduce strength and make it much more prone to cracking or breaking under load. In rescue work, encountering rotten ice means you should treat the surface as highly dangerous and avoid stepping on it unless necessary, using safer ice testing, flotation, and reach devices to assess or reach a victim.

Clear ice, by contrast, forms with fewer air pockets and a more uniform crystal structure, making it typically stronger. Drift ice refers to floating chunks that move with currents, not a specific optical appearance, and pack ice is a broad sheet of sea ice; neither of these inherently describes milky opacity from trapped air.