La Brea Tar Pits FAQsShare
When did the animals found at Rancho La Brea live in this region?
The extinct animals discovered at Rancho La Brea were trapped in the asphalt between 11,000 to 50,000 years ago. They may have lived in the Los Angeles region for much of the last 100,000 years. Before that time the Los Angeles Basin was covered by the Pacific Ocean.
How old is the oldest fossil from Rancho La Brea?
Using the Carbon-14 radiometric dating method, some of the older fossils include a dire wolf and a saber-toothed cat from Pit 91 each dated at 44,000 years old, a coyote from Pit A dated at 46,800 years old, and wood from Pit 16 dated at 55,000 years old. These dates are estimates based on the amount of Carbon-14 remaining in the specimens. The real age of these specimens may be as much as 5,000 years more than the radiocarbon estimates.
How many fossils have been removed from Rancho La Brea?
Since 1906, more than one million bones have been recovered representing over 231 species of vertebrates. In addition, 159 species of plants and 234 species of invertebrates have been identified. It is estimated that the collections at the Page Museum contain about three million items. Our current Project 23 excavation may, when completed, double this number.
What are the most common animals found?
Dire wolves are the most common large mammals from Rancho La Brea, with about 4,000 individuals represented in the Page Museum collections. The remains of over 2,000 individual saber-toothed cats rank second and coyotes rank third.
How did the animals become trapped?
Asphalt is very sticky, particularly when it is warm. The warm temperatures from late spring to early fall would have provided the optimum conditions for entrapment in asphalt. Small mammals, birds, and insects inadvertently coming into contact with it would be immobilized as if trapped like flies on flypaper. The feet and legs of heavier animals might sink a few inches below the surface. Depending on the time of day or year, strong and healthy animals might have managed to escape, but others would have been held fast until they died of exhaustion, or fell prey to passing predators. A single, mired large herbivore might attract the attention of a dozen predatory birds and mammals, some of which would in turn become trapped and provide more food for other carnivores. This cycle was repeated throughout the time that fossils were accumulating at Rancho La Brea. It has been estimated that one entrapment episode involving ten large mammals every decade would furnish more than enough fossil remains to account for all the large mammal and bird bones collected since the turn of the 20th century, totalling over 1 million.
Why are the skeletons on display in the Page Museum brown in color?
The brown color results from staining by the asphalt in which the bones were preserved.
What was the Ice Age like in the Los Angeles Basin?
Some of the plant species found in these fossil deposits now only live along the summer fog belt from San Luis Obispo to Oregon or on the Channel Islands. Other species occur today in the southern Sierra Nevada Mountains between 4,000 and 6,000 feet elevation. This suggests that the late Pleistocene climate at Rancho La Brea was cooler and wetter than it is today.
Are scientists still excavating at Rancho La Brea?
Yes. We are currently working on Project 23, a large salvage excavation that could double the size of our collections. In June of 2006, the Los Angeles County Museum of Art (LACMA) began work on a new underground parking garage. During the course of construction, 16 new asphaltic fossil deposits were discovered. These deposits were divided into 23 enormous intact blocks that were lifted out of the ground, crated with wooden planks into tree boxes and moved by crane and truck to their present location immediately north of the Pit 91 complex. Excavation began in 2008. The boxes are on view to the public and excavators work seven days a week to recover the fossils.