La Brea Tar Pits - Los Angeles, USA

January 2, 2014

The La Brea Tar Pits are a group of natural asphalt pits that has seeped up from the ground in this area for tens of thousands of years

Entrance to George C. Page Museum

From time to time, the asphalt would form a deposit thick enough to trap animals, and the surface would be covered with layers of water, dust, or leaves. 

Animals would wander in, become trapped, and eventually die. Predators would enter to eat the trapped animals and also become stuck.  

You can see gas bubbles emerging from this tar pit

Of more than 100 pits, only Pit 91 is still regularly excavated by researchers and can be seen at the Pit 91 viewing station.

Pit 91

To avoid disrupting nearby construction, some fossils were packaged in boxes at the construction site and moved to a compound behind Pit 91. This is called Project 23.

Project 23

The following block of asphalt shows the amazing density of specimens found in the excavations. You can see how the bones will appear if the asphalt matrix was clear.

Block of bones from Pit 81

Inside the museum, you can see the laboratory where information about each specimen is written on a catalogue page and checked twice for accuracy before the fossil is stored in the research collection.

Palentology Laboratory

The park is known for producing myriad mammal fossils dating from the last glacial period. While mammal fossils generate significant interest, other fossils, including fossilized insects and plants, and even pollen grains, are also valued.

Saber-toothed cat

These fossils help define a picture of what is thought to have been a cooler, moister climate in the Los Angeles basin during the glacial age.

Ground Sloth

Radiometric dating of preserved wood and bones has given an age of 38,000 years for the oldest known material from the La Brea seeps.

Scene depicting a Saber Tooth hunting a Ground Sloth

The pits still ensnare organisms today, so most of the pits are fenced to protect humans and animals.

Antique Bison - Most common plant eater around the area

Only one human has been found, a partial skeleton of the La Brea Woman dated to approximately 10,000 calendar years (~9,000 radiocarbon years) BP, who was 17 to 25 years old at death and found associated with remains of a domestic dog, and so was interpreted to have been ceremonially interred.

Camel - Camels originated in North America 45 million years ago

Tar pits around the world are unusual in accumulating more predators than prey.

Columbian Mammoth

The reason for this is unknown, but one theory is that a large prey animal would die or become stuck in a tar pit, attracting predators across long distances.

This predator trap would catch predators along with their prey.

Naegele's Giant Jaguar

Another theory is that dire wolves and their prey may have been trapped during a hunt. Since modern wolves hunt in packs, each prey animal could take several wolves with it.