The La Brea Tar Pits, located in the heart of Los Angeles, are a unique geological site offering a fascinating glimpse into the Ice Age. Natural asphalt has seeped up through the ground over tens of thousands of years, trapping and preserving a remarkable collection of fossils. This site is not just a museum, but also an active paleontological research area, allowing visitors to witness ongoing scientific discoveries.

La Brea Tar Pit

What are the Tar Pits?

The “tar” in the La Brea Tar Pits is not actually tar, but asphalt, the residue of petroleum after the lighter components have evaporated. The oil originates from a shallow sea that existed in the area about 25 million years ago. Microscopic plankton died and settled on the seabed, eventually transforming into oil. Tectonic activity uplifted the region, causing oil to seep through cracks in the Earth’s crust, forming the tar pits. The sticky asphalt acted as a natural trap, ensnaring animals and preserving their remains.

Fossils of the Ice Age

The La Brea Tar Pits boast an astounding array of Ice Age fossils, with over 600 species discovered, including tiny insects and majestic megafauna. The most famous fossils include:

  • Columbian Mammoths: These massive creatures were common in the area. The museum displays a large Columbian mammoth, and pit 9 alone trapped at least 27 of them.
  • Dire Wolves: Thousands of dire wolves have been found at the Tar Pits. These predators were drawn to the pits by the promise of easy prey, often becoming trapped themselves.
  • Saber-toothed Cats: These iconic predators also fell victim to the sticky asphalt.
  • Giant Ground Sloths: Skeletal remains of ground sloths can be seen at the museum.
  • Mastodons: Similar to mammoths, these large herbivores were also found in the area.

These fossils are exceptionally well-preserved due to the unique properties of the asphalt. The stickiness of the asphalt allowed scientists to examine the most subtle details on these remains, including the teeth of carnivores.

The Ecology of the Tar Pits

The Tar Pits provide a unique window into the Ice Age ecosystem. Beyond the megafauna, the site contains fossils of plants, insects, pollen, and even poop. The plant fossils include trees such as junipers and California sycamores, which help scientists understand the weather patterns of the Ice Age. A recent study identified a previously unknown juniper species, Juniperus scopulorum, also known as the Rocky Mountain juniper, and radiocarbon dated the junipers in the pits. This study showed that the two juniper species present, J. californica and J. scopulorum, alternated in presence depending on climate, with J. scopulorum being an extreme example of a plant becoming locally extinct. Researchers found that the J. scopulorum could not survive the drought and wildfires that occurred in the region.

The fossil record at La Brea reveals that about 90% of the mammal fossils found are of carnivores. This is because predators were attracted to the trapped herbivores, leading to them becoming trapped as well. The pits paint a rich picture of life in the Pleistocene, with fossils dating back 50,000 to 10,000 years ago. The end of this period saw the extinction of many megafauna, possibly due to a combination of climate change and human activity. Increased human populations, coupled with severe drought and warming temperatures, caused plant food sources to dwindle, leading to the decline of herbivores and subsequently carnivores.

Visiting the La Brea Tar Pits

Visitors can explore the outdoor area for free and see various tar pits, including one with a mock-up of an animal trapped in asphalt. The museum offers a deeper look into the site’s scientific history and displays many fossils, including a Columbian mammoth and a wall of dire wolf skulls. In the Fossil Lab, visitors can watch scientists at work cleaning and preserving fossils. Outside the museum, excavation sites allow visitors to observe the process of unearthing new fossils. The La Brea Tar Pits are a testament to the past and provide valuable information that can inform our understanding of current environmental issues.

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