Black ice looks black because it is so transparent that the asphalt of the road shines through. This insidious phenomenon occurs when melted ice or snow freezes again and forms a thin, invisible layer on the roadway. Because motorists cannot see this ice layer, dangerous situations arise and cars sometimes slip in all directions.
Black ice is also found at sea
This phenomenon can also occur when it rains and the temperature is below 0 ° C, causing the wet road to freeze. It is then a form of black ice. At first glance it looks like nothing is wrong, but in fact it is insidiously slippery.
Black ice is also a well-known term in shipping and poses a potential threat to ships. Black ice at sea is not water that has melted and then frozen again, but is ice that has formed under high pressure in a glacier. If the pressure is high enough, the ice will become transparent.
Rain makes the road very slippery© YOUTUBE
On December 1, 2013 there was a layer of black ice on the American highway Interstate 290 when it had rained and the water on the cold road was immediately frozen. Three trucks and more than 60 cars were involved in a huge chain collision on a 500-meter stretch of road.
The ice lay on the slope downhill, meaning that upcoming drivers only saw the crashed cars when they were over the top.
At that time they were no longer able to brake, which made the havoc much greater.
Melted snow freezes again
Black ice usually occurs because snow melting water flows onto the road during the day. If the temperature drops at night, water freezes.
1. DAY TEMPERATURE MELT SNOW AND ICE
During the day the temperature rises above freezing. This melts the snow on the roadside.© KEN IKEDA MADSEN
2. WATER IS RINSE OFF
The melt water flows over the roadway and possibly takes road salt, so that the frost has even more grip on the asphalt.© KEN IKEDA MADSEN
3. NIGHT FROST FORMS A BLACK LAYER OF ICE
During the evening and night the temperature drops below freezing. The melt water on the road freezes, and the ice layer is so transparent that the dark asphalt remains visible.© KEN IKEDA MADSEN