Inland Otago and South Canterbury experience much colder winters than the rest of New Zealand, thanks to surrounding mountain ranges that cut these inland basins off from the moderating influence of the not-too-distant sea. While temperatures well over 30 ºC are common here in summer, its not unheard of for overnight frosts to plunge below minus 20 ºC a few months later in the middle of winter, making for a continental-style contrast between seasons here despite New Zealands moderate oceanic setting.
During the deep chill of winter here many small lakes and streams will partly or completely freeze over for days or sometimes even weeks at a time. Once an ice cover has formed it is often subjected to a wide range of conditions such as repeated frosts, snowfalls, strong winds and partial melting and re-freezing, its surface becoming more and more intricately patterned the longer it remains intact.
The pond in this photograph had been frozen over for two or three weeks by the time I took this photograph, and, in the time since it had first frozen over, its surface had lowered by about half a metre as water had drained out from under the ice. As well as creating striking patterns along the shoreline, this lowering of the surface had also slowly impaled the ice on the tips of rocks that had originally been just below the surface. This caused the ice to fracture, creating radiating patterns of cracks that then filled with clear ice when upwelling water from below froze upon reaching the surface.