Frazil
Frazil ice grows in supercooled (below 32 F) turbulent streams, brooks, rivers, and artificial channels and trenches. Microscopic discoids and spicules grow into blades that form surface border ice, and below in flocs adhered to walls and the bottom, loosely called anchor ice. Crystal breakage forms more seed crystals, known as secondary nucleation.
A Classic Step-Pool Brook In Rugged Glacial Moraine: Splashing, mist, evaporation and spray will freeze onto airborne dust, bacteria and fungi to make seed crystals that fall into the turbulent water.
Flash Frozen Splashcicles: Supercooled water also forms ice in brooks when it impacts a cold surface, such as splash upon cold rocks and icicles.
Fresh Frazil Border Ice In Star And Tree Forms
Upside Down, Three-Inch-Long Piece Of Fresh Frazil Border Ice: The vertical crystal growth was up to 1.5 inches long.
Enclosing Frazil Border Ice Between Boulders
Metamorphosed Frazil
Secondary Frazil Border Ice Growth Above Water #1
Secondary Frazil Border Ice Growth Above Water #2
Border Ice And Frazil Flocs Frozen To A Mid-Stream Boulder: Water level drop of about 6 inches exposed the flocs. Sub-borders (left of center) formed from melt and vapor had grown in air from the flocs during the previous three days. Border ice with flocs below are frozen to a huge boulder in the distance.
A trench at left covered with a sheet of frazil ice beneath which more frazil caught as water moved in the trench. The foreground shows a removed chunk. The frazil first formed within a steep upstream roadside trench right after a mid-winter thaw. The trench was dry when I photographed it during the New Hampshire thaw of January 19, 2023.
Blades Under a Surface Sheet: A sheet about 1 mm thick had frozen over a trench but in doing so had incorporated frazil ice. The ice then grew downwards and caught more frazil coming down stream. There are many examples of tiny dendritic growth, such as at the lower left center.
Blade Growth Detail: This is a blade on its side. The long part, about 5 cm in maximum length, contains evidence of flow before it refroze.
Dendritic Discoids: There a few discoids with dendrites on one side. Their multi-mm size is evidence that they started far upstream. White dots are air bubbles.
Spicules and Sheet Stress Contours: Clusters of spicules and curvilinear stress contours generated by the weight of the sheet as it sagged into the air below while the trench dried or ran out of water. Dark areas are clear black ice.
Melting Frazil Border Ice