La Mancha Negra

La Mancha Negra means 'The Black Stain' in Spanish. It denotes a mysterious black substance that has oozed from (or on) roads in Caracas (Venezuela), first appearing in 1986. Since its first appearance, La Mancha Negra has caused more than 1,800 deaths in the five years before 1992. La Mancha Negra has been described as an inch-thick, slippery, greasy, black, thick substance that has the consistency of chewed bubble gum.

In 1986, a smudge some 50 meters long was noticed by workers as they patched the 30-year-old asphalt on a highway between Caracas and its airport. Initially, concerns for La Mancha Negra – as it was soon called - were low, but it soon spread. As much as 13 kilometers of highway were soon covered with the unknown bituminous material that contracted and expanded with the weather. It was found to grow when conditions were humid but to shrink when it was cold and dry. It seemed to prefer tunnels and the uphill slopes outside the airport. By 1992 the stain had spread throughout the city of Caracas.

La Mancha Negra made roads slippery, causing vehicles to crash into one another or run off the road. Experts have tried to pinpoint the chemical composition, but were unable to reach a conclusion in 1994.

In 1991, a group of experts consulted President Carlos Andrés Pérez about the problem but could not pinpoint the cause of the substance.[3] 1,800 deaths were then attributed to La Mancha Negra in the five years before

Finally, the government poured tons of pulverized limestone over the La Mancha Negra to 'dry it up'. This seemed to work for a while, but created a different problem; the roads then became so dusty that drivers and local residents complained that the air was unbreathable.

Early 1996, the roads became slick with the substance once more, due to the lack of maintenance, low rainfall and the generally poor condition of vehicles in Caracas. Special cleaning equipment was brought in from Germany, and the phenomenon seemed to have abated for several years thereafter. However, La Mancha Negra reappeared in 2001 on several roads in Caracas.

The most accepted theory is that La Mancha Negra is the result of countless old cars leaking their fluids, such as cheap petrol, motoroil and brake fluid, over the roads[1]. Researchers now think that La Mancha Negra is just an accumulation of those fluids with dust on the roads that over time formed a paste. The roads literally shine with the oil drippings of thousands of cars that labor up an incline into the city each day.

[1] Regina Garcia Cano: On Venezuelan roads, old cars prevail, break down everywhere in AP News - 2022. See here.