The black spot

"Black spot" (La Mancha Negra) — a mysterious black substance emanating from the streets Caracas , Venezuela.

The substance first appeared as a 50-yard-long trail discovered by workers laying a 30-year-old highway between Caracas and its airports.

At first, this did not cause much concern, but soon the spot expanded and covered eight miles of highway. The unknown material grew when the weather was hot and humid, but shrank when it was cold and dry. Despite its elastic texture, the stain made the road extremely dangerous, causing vehicles to crash or fly off the road. 

In 1991, a group of experts consulted with the President Carlos Andres Perez about this problem, but could not determine the cause of the appearance of this substance. 3 Between 1987 and 1992, 1,800 deaths were attributed to the "Black Spot".

The black spot is described as a thick, greasy black substance with the consistency of chewing gum, although Venezuelans describe roads as if they are "covered in ice." 

The team of the Ministry of Transport and Communications concluded that the "Black Spot" consisted of dust, oil and various organic and synthetic materials.

Several theories have been proposed to explain this phenomenon, but none of them have established its exact nature. 

One theory was that the "black spot" was oil seeping into low—quality asphalt, causing oil to leak when the temperature rises. However, the Minister of Transport and Communications stated that the composition of asphalt is not related to the formation of the substance. 

Others believe it's the result of countless old, leaky cars throwing liquids onto the streets. Professor Giuseppe Giannetto, commissioner of the Ministry of Transport and Communications, believes that the "Black spot" was an accumulation of dust and car oil on the roads, forming a paste.

Finally, some believe that sewage from nearby neighborhoods leaked under the asphalt, causing a chemical reaction that caused the roads to crack.