黑黑的 反而不是黑冰
黑冰是因為太乾淨了
一般人肉眼不易發現
才叫做black ice
照片中人行道上像是天師畫符的痕跡
經由校長的攝影技術呈現出來
才是black ice
http://en.wikipedia.org/wiki/Black_ice
Black ice, also known as "glare ice" or "clear ice," typically refers to a thin coating of glazed ice on a surface, often a roadway. While not truly black, it is transparent, allowing the usually-black asphalt/macadam roadway to be seen through it, hence the term. It is unusually slick compared to other forms of roadway ice.
Because it contains relatively little entrapped air in the form of bubbles, black ice is transparent and thus very difficult to see (as compared to snow, frozen slush). In addition, it often is interleaved with wet road, which is identical in appearance. For this reason it is especially hazardous when driving or walking because it is both hard to see and unexpectedly slick.[1]