Frozen waterfall and a video of supercooled water turning into frazil ice

Abstract

In early January 2018, after days of subfreezing temperatures, a 20 m waterfall became mostly frozen with supercooled water pouring over the top of the frozen parts of the fall. A video was taken of the waterfalls and supercooled turbulent water flowing on the frozen surface as it turned into frazil ice right before our eyes. Frazil ice consists of random crystal orientations and can be considered as a quasi-solid substance, a slush. The majestic Looking Glass Falls is located in Pisgah National Forest, Transylvania County, in western North Carolina, USA. One of the authors (CC) made the trip in very adverse weather of −15 °C to take the video of turbulent supercooled water flowing and turning into frazil slush ice. For background material and context, an interesting chart of metastable water states, which includes supercooled water, is compared to the stable states of water with which students are familiar. Nucleation is briefly discussed so students can understand how supercooled water crystallises. Finally, a discussion of danger is included with video footage of a young lady being rescued after she fell in up to her waist.