What causes black ice?

Answer 1

Freezing temperatures and water....on top of black asphalt....

Answer 2

Black ice is a term frequently given to roadway ice. It forms the same way any other ice does -- when temperatures drop below freezing and earlier rains or melted snow freeze. But if the ice is clear, it looks invisible against the black road surface -- thus the term "black ice."
When you have what looks like a dry road surface, but it appears darker in color and more dull-looking, that's at least a indication that black ice might be present

Answer 3

The combination of the already snowy conditions coupled with heated car exhaust causes the snow to melt and then re-freeze. Black ice is extremely dangerous because before the sun comes up or after it goes down, it is nearly invisible - until your car tires hit it. After that, all bets are off. Unfortunately, too many people have no winter driving skills in states where they need them (like Minnesota!) and their first instinct is to slam on their brakes. On black ice, this can be incredibly dangerous, and cause a chain reaction of brake lights behind that car, sometimes ending in a bigger mess than just black ice.

Answer 4

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 also is unusually slick compared to other forms of ice on roadways.[citation needed]

It is usually deposited by extremely cold rain droplets, mist, or fog. The process of freezing is slowed down due to latent heat given off in sublimation, allowing the rain droplets to flow and merge together on the surface forming a film before freezing into clear ice. Nevertheless, 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, rime ice, or other typical forms of ice on roadways). In addition, it often has a matte appearance rather than the expected gloss; and often is interleaved with wet pavement, which is identical in appearance. For this reason it is especially hazardous when driving or walking because it is both hard to see and extremely slick.

Black ice may form even when the ambient temperature is several degrees above the NTP freezing point of water (0°C). This occurs typically (and treacherously) when terrain contours and/or prevailing winds cause a local steep differential of atmospheric pressure and/or temperature, or when the atmosphere has warmed up after a prolonged cold spell that leaves the temperature of the ground and roadway well below the freezing point.

Bridges and overpasses can be especially dangerous. Black ice forms first on bridges and overpasses because air can circulate both above and below the surface of the elevated roadway, causing the temperature to drop more rapidly than on regular pavement.

"Black ice" may also be cited as the cause of a car crash when, in fact, the real root cause may have been excessive speed, inattention, or some other fault on the part of the driver

Answer 5

Frozen water on asphalt is correct, but only part of the story. The water can come from freezing rain, melting snow, or condensed freezing fog: all will cause black ice and treacherous driving.

Answer 6

Let's say water (melted snow or ice, usually) gets onto a highway and refreezes at night. It freezes into an earily normal looking patch of pavement, and people don't know that it's ice until it's too late.

Answer 7

Slowly freezing mist or rain on a dark (black) surface -- the liquid is warmed by the surface and therefore freezes slowly and smoothly, without air bubbles or roughness to make it appear white. It's not really black, it's transparent.

Answer 8

Black ice isn't black. Its thin ice on asphalt.

Answer 9

Black ice on roads is because of the color of the road.
Black ice in streams is pollution.

Answer 10

it occurs when water freezes on top of ice. then it becomes as hard as stone and thick, smooth trecherous to walk or drive on, as salt and grit cannot penetrate it at all