La Brea Tar Pits: Where Ice Age Mammoths Walked on Wilshire Boulevard

by Kathy Hrechka, MSDC member and editor of The Mineral Mite

The George C. Page Museum and La Brea Tar Pits, Los Angeles, CA.

One of my bucket list destinations was recently checked off – having an adventure to the famous La Brea Tar Pits with my husband Ken. On our 12-mile drive from LAX to the La Brea area on Wilshire Boulevard, we passed more than 20 working oil pumps among the residential neighborhoods. That was my indicator we were close to our destination.

We toured the George C. Page Museum and Tar Pits, witnessing larger-than-life, reconstructed Ice Age fossil mammoths, mastodons, camels, sloths, wolves, saber toothed cats, and a fossil lab. Most featured bone structures were more than 80% original. We learned that the La Brea Tar Pits is an active paleontological research site despite being in the middle of heavily urbanized Los Angeles, California. The pits contain fossilized remains of millions of plants and animals dating between 50,000 and 100,000 years ago.

A unique combination of complex geologic events is responsible for the rich accumulations of fossils found at the tar pits. Oil formed, tectonic activity forced it to the surface, and sediments were deposited. Originally the pools were composed of crude oil that originated below Earth’s surface. The oil is a mixture of heteroatom (i.e., not hydrogen or carbon) compounds, hydrocarbons, metals, and inorganic compounds.

In the early 1900s, when dozens of wells pumped oil out of the ground in the area, workers dug 96 pits looking for fossils and removed over one million fossils. The excavation work continues to this day and the La Brea Tar Pits Museum now houses nearly five million fossils.

For over a century, researchers at La Brea Tar Pits and Museum have unearthed the world’s most complete record of what life was like at the end of the Ice Age. So how did different types of fossils end up in the tar pits together? For thousands of years, crude oil has been naturally rising up to the surface forming shallow puddles of sticky goo called asphalt seeps. It was easy for animals to get trapped in the sticky goo. Tar pits were created by excavating ancient asphalt seeps.

Besides the museum, we also enjoyed the famous tar pits outdoors, noting methane gas bubbling up and creating circular rings as the gas escaped from the tar pits. It was fun to guess the locations of future gas bubbles as the pit was quite active, continuously belching gas. Outdoors, fossil excavations continue at locations referred to as Pits 91 and 23. We were not able to observe researchers and volunteers actively working at Pit 91 because the gates were closed to visitors. Pit 23 contained 23 crates of excavated material available for current and future study.

It was amazing to witness such a cool natural phenomenon from the Ice Age in the middle of 21st-century Los Angeles. Here are some photos from the museum with captions. I hope these images from the site and museum will inspire you to visit.

When excavators unearthed giant leg bones in Pit 9 from 1914 to 1915, they made a major find. Most of La Brea’s Columbian mammoth and American mastodon fossils came from this pit.
Block of bones from Pit 81: This block of asphalt containing fossil bones was removed from one of the smallest pits in 1914. It shows the amazing density of specimens found in the excavations.
Columbian mammoths, the most common mammoth species in North America.

The Columbian mammoths were the most common mammoth species in North America, standing twelve feet tall, weighing 17,000 pounds. Mammoths, mastodons, and their living cousins, elephants belong to a group of mammals called proboscideans. The name comes from the proboscis, or trunk, a feature many of these animals share.

The first proboscideans appeared in Africa about 55 million years, ago and over many generations evolved into more than 150 different species spread around the globe. Discoveries at La Brea Tar Pits show that some of their descendants, Columbian mammoths and American mastodons, were in the Los Angeles Basin 50,000 years ago.

American mastodon (Mammut ameriananum): 2 million to 10,000 years ago. Shorter and stockier that their mammoth cousins, mastodons separated from the rest of the proboscidean family tree millions of years ago. Though similar to mammoths, mastodons evolved differently shaped skulls, tusks, and teeth.
California Saber-Toothed Cats were as large as African lions but were more heavily built, with 4-inch fangs. More than 2,000 have been found in the pits.
Harlan’s ground sloth: around 1,500 pounds and over nine feet in length. The living relatives of these ancient giants include armadillos and small tree sloths.
Antique bison: Scientists believe that these bison migrated to La Brea annually when grass was plentiful.
Extinct camel: the vertebrae suggest that these camels only had one hump. The remains of only 36 camels were discovered at La Brea.
Fossils being worked on at the lab, close to where they were originally found.

Every fossil in this lab was excavated right outside at Project 23. The name refers to the 23 crates of fossils to clean and archive that came from the excavation site for a new art museum next door to the La Brea Museum.

This fossil on the lab floor (upside down position) is the skull of Zed, the most complete Columbian mammoth ever discovered at La Brea Tar Pits. It was excavated in 2008 as part of Project 23.
Blocks of Ice Age fossil-rich material unearthed from Project 23.

In 2008, excavation for a neighboring art museum unearthed 23 6’ x 6’ x 6’ blocks of Ice Age fossils. They were donated for continued research at La Brea, referred to as Project 23.  The millions of new fossils from Project 23 are helping to reconstruct the environment of the Ice Age of Los Angeles. New finds include bones of saber-toothed kittens, an American mastodon baby, and young horses and camels.

A newly opened Project 23 crate ready for study. It was excavated in 2008 from the construction site of a new art museum adjacent to the tar pits.
Recreation of a proboscidean descendant stuck in the percolating La Brea Tar pit along Wiltshire Boulevard, Los Angeles, California.
Fresh tar oozing up through the concrete surface in front of the museum. Sites like this are common in the local area.

The information provided in this article is reproduced from exhibits in the museum. All photographs are by Kathy Hrechka.