All Ice is Not Created Equal

I saw something on the TV news the other day about that blue ice. I didn't know about the role that air bubbles play in ice formation until then, but I knew what blue ice is. I haven't been out on the ice for a long time, maybe decades, but the ice conditions used to be frequently discussed by the guys at work and in the bars, and probably still is. Blue ice is the original ice that is formed when the lake water freezes. We call the other type "slush ice". That's the white layer that is bonded to the blue ice in the photos. Slush ice is formed when the snow on top the blue ice melts and re-freezes. Sometimes it really is slushy, but often it will freeze hard when the weather turns cold again. Slush ice is not to be trusted, as it has little weight bearing potential. Sometimes there is a layer of liquid water between the blue ice and the slush ice, formed when accumulated snow weighs the blue ice down and slightly submerges it. You can be walking or driving on the ice and suddenly break through the slush ice layer.  This can be inconvenient and down right scary, but usually not dangerous if there is plenty of blue ice underneath it all. If you ask somebody what the ice is like on the lake, the proper response would be, "so many inches of blue ice and so many inches of slush ice". If he just says "so many inches of ice", he doesn't know what he is talking about and you should get a second opinion before venturing out.