The La Brea Tar Pits: Wonder of Wonders in Los Angeles, California

Every time I bring my students for their yearly field trip to the La Brea Tar Pits, it never fails to amaze and excite me. I never could fathom how such a place exists in the bustle of the city of Los Angeles and to know that this historical geological place really exists! It simply catapults me back millions of years ago when the area of Los Angeles and Rancho La Brea lay beneath the surface of the Pacific Ocean. Who would have thought that this great city of multiple businesses and heavy traffic was simply the ocean floor long, long ago!

A short orientation video is shown at the Page Museum to visitors prior to their exploration of the tar pits. The museum itself has a display of the excavated bones of the prehistoric animals found in the tar pits. A brochure and accompanying guidebook give visitors a detailed history of the pits. An excerpt from their latest guidebook reads: When the ocean levels receded some 100,000 years ago, the area of Rancho La Brea became land. New layers of gravel, sand and clay formed by the erosion of the emergent hills, and settled on top of the much older marine sediments full of oil. At Rancho La Brea, the crude oil has been seeping out of the ground through conduits and fissures in the coastal plain sediments for the past 40, 000 years, the seeps forming pool in the low-lying areas.

Over tens of thousands of years, this produced the cone shaped asphalt deposits at Rancho La Brea. With its numerous asphalt seeps, Rancho La Brea was a hazardous place for animals to roam. Wandering animals would often pass by and unknowingly venture into the camouflaged asphalt and become trapped; pack of dire wolves, or a saber toothed cat would attack the mired animal and even each other. One of the most extraordinary aspects of the deposits at Rancho La Brea is the preservation of not just a few fossils, but instead an entire prehistoric ecosystem. From the smallest plant fragments to the largest mammals, the fossilized remains of Rancho La Brea number well into the millions. The evidence is complete enough that scientists can reconstruct the environment that existed in Los Angeles 12-40 thousand years ago!