The mysterious black slime has claimed the lives of 1,800 people within the first five years after it appeared on a highway near Caracas.
In 1986, in Venezuela, a strange slime resembling toxic waste oozed from a heavily trafficked highway connecting Simón Bolívar International Airport to the capital, Caracas. Just as quickly as it appeared, the mysterious substance known as La Mancha Negra (the Black Spot) began to spread, transforming the highway into a death trap for drivers, according to IFL Science.
The unknown slime became a threat to many drivers on the highway. (Photo: Pinterest)
The black slime first appeared on a 46-meter stretch of asphalt on the highway and continued to expand until it covered 13 kilometers with a thickness of 2.5 centimeters in some areas. As dark as tar, the slime had a consistency similar to chewing gum. In the first five years after its emergence, La Mancha Negra claimed the lives of 1,800 people who attempted to navigate the road it had “devoured.”
Although it disappeared briefly without explanation in the 1990s, La Mancha Negra resurfaced in 2001 and remains a mystery. To this day, it continues to spark numerous conspiracy theories.
One hypothesis is that the slime was created from a batch of low-quality asphalt, explaining its tar-like appearance. Asphalt contains tar, which is extremely sticky when heated. Like tar, one of the key characteristics of La Mancha Negra is its reaction to weather, expanding in hot and rainy conditions and contracting when temperatures and humidity drop.
Another hypothesis suggests that the slime is a result of natural crude oil seepage from nearby oil fields. The city of Caracas is located near the Orinoco belt, which uses pipelines to transport heavy oil to Caracas and many other Venezuelan cities. However, Ramanan Krishnamoorti, a professor of chemical and petroleum engineering at the University of Houston, stated, “Typically, leaks from shallow oil wells require fault points and are unlikely to spread across a 13-kilometer stretch. Furthermore, heavy oil usually sinks and does not seep to the surface.”
Reinaldo Gonzalez, a lecturer in the petroleum engineering department at the University of Houston who was in Venezuela during the 1986 incident, believes the simplest plausible explanation is that separate batches of processed asphalt were improperly mixed, causing one to “float” to the surface, creating a slightly sticky black streak on the road.
According to another theory, raw sewage from nearby slums is the cause, leading to the chemical degradation of the asphalt as it flowed down the sloped road. Others suggest that it could be burnt rubber from tires or oil leaking from vehicle engines.
One leading hypothesis speculates that faulty asphalt is the result of poor government budget management, cutting corners by using substandard materials in road repairs and maintenance. There is even speculation that both the government and private companies profited greatly by repeatedly conducting road repairs and extended clean-up efforts.
In 2001, when the slime reappeared, Caracas Mayor Freddy Bernal claimed he had previously hired people to throw bags of used oil onto the highway at night to tarnish his reputation. Although the samples contained 60% brake oil and 40% used oil, indicating that the substance was deliberately created, Bernal’s claims lacked proof and did not explain the first occurrence of the slime.
Nevertheless, the Venezuelan government spent millions of dollars trying to analyze the composition of the slime. Despite hiring experts from the U.S., Canada, and Europe, chemical tests could not verify what was inside the slime. Authorities also made several attempts to wash it away with water, air, and scrape the sticky substance off the road, but all efforts were unsuccessful. The slime seemed to continue to spread. They even tried drying it out by pouring crushed limestone onto the road. However, this only created more problems due to dust from the limestone affecting air quality and visibility in the area.
Traffic jams became common on the crowded highway. Red warning signs were erected to remind drivers to slow down. Local residents and taxi drivers began to avoid driving on the highway. The area was blocked off four nights a week for workers to temporarily repair the road.
Despite the precise details about the slime remaining contentious, it caused real chaos in Venezuela for many years before disappearing abruptly without explanation in the 1990s. Researchers still do not know what stopped La Mancha Negra. They speculate that the major landslides in 1999, which prompted the construction of new roads, could be part of the reason. However, they did not stop La Mancha Negra, as it reappeared in 2001. Reports on the current status of La Mancha Negra indicate that it ceased in the early 2000s.
