The question of how many “tar pits” exist globally introduces a fascinating geological phenomenon responsible for trapping and preserving ancient life. While the term “tar pit” is widely used, it is scientifically inaccurate; the sticky substance is not tar but a naturally occurring form of petroleum. These formations are more correctly identified as natural asphalt or bitumen seeps, where underlying crude oil deposits find a path to the Earth’s surface. A simple count is difficult due to the complexities of geology and the variable nature of these unique sites.
What Defines a Natural Asphalt Seep?
The substance commonly mistaken for “tar” is actually asphalt, or bitumen, a residue of crude oil. Tar is a synthetic material produced by the destructive distillation of organic matter like coal or wood, containing different chemical properties than its natural counterpart. Natural asphalt is a dense, black, sticky hydrocarbon mixture that forms when liquid petroleum migrates upward from deep underground reservoirs.
This geological process begins when crude oil travels through fissures or porous layers within the Earth’s crust. Once the liquid petroleum reaches the surface, its lighter, more volatile components—such as gasoline and kerosene—evaporate upon exposure to air. This weathering leaves behind the heavy, non-volatile residue known as asphalt, which accumulates in depressions or pools.
The remaining asphalt is a highly viscous, sticky material composed primarily of carbon and hydrogen, often mixed with minerals. Because the formation is continuous, with new material seeping up from below, the asphalt remains soft and mobile for long periods. This constant replenishment and sticky nature make these seeps effective natural traps for unsuspecting animals.
Why a Global Count Is Elusive
Providing a precise number of natural asphalt seeps around the world is impossible because no definitive global census exists. The primary difficulty lies in defining what constitutes a “tar pit,” as seeps vary dramatically in size and significance. They range from massive, commercially viable asphalt lakes to small, temporary puddles or intermittent oil slicks.
Many small, localized seeps in remote areas remain undocumented, and others are too dynamic to count reliably. Seepage rates are often intermittent, meaning a site might appear active for a time, then dry up or become covered by vegetation, making detection difficult. Furthermore, a seep is often only counted if it has demonstrated significant paleontological importance, which limits the tally to only a few dozen globally recognized sites.
The sheer number of offshore oil seeps also complicates any count, as many are located deep on the ocean floor. For example, over 1,600 distinct seep zones have been identified in the Gulf of Mexico alone using satellite technology. While these offshore seeps release substantial amounts of oil, they do not form the terrestrial “tar pits” that capture and preserve fossils.
The World’s Most Significant Sites
Since a global number is unattainable, attention focuses on the few sites recognized for their size or scientific contribution. The two most famous examples are the Pitch Lake in Trinidad and Tobago and the La Brea Tar Pits in Los Angeles, California. These sites are famous due to their unique properties and rich records of natural history.
The Pitch Lake, located in La Brea, Trinidad, is the world’s largest natural deposit of asphalt, covering approximately 100 acres and reaching depths of about 250 feet. This massive deposit is a major commercial source, having supplied asphalt for roads worldwide since its rediscovery in 1595. The surface is capable of being walked upon, yet the asphalt beneath is slowly churning, sometimes revealing ancient artifacts or tree trunks.
The La Brea Tar Pits are a cluster of seeps known for their unparalleled collection of Ice Age fossils from the Pleistocene epoch. Over 3.5 million specimens have been recovered, including the remains of saber-toothed cats, dire wolves, and mammoths, trapped over tens of thousands of years. The asphalt, known locally as brea, acted as a perfect preservative, creating a comprehensive window into the megafauna of the last Ice Age.
Other notable examples include Lake Bermudez in Venezuela, the world’s second-largest natural asphalt lake, and the McKittrick Tar Pits in California. These sites, along with others in places like Azerbaijan and Peru, underscore that while the phenomenon of a “tar pit” is geologically rare, it appears in specific oil-rich regions across the globe.