La Brea Tar Pits, CA
On July 15th, 2016; Becky, (my wife) was asked to sing at a wedding in Disneyland. While we were there we visited the Rancho La Brea Tar Pits in Los Angeles.
One hundred thousand years ago, the area occupied by Rancho La Brea lay beneath the surface of the Pacific Ocean. At the onset of the last glaciation of the Pleistocene Ice Age the sea retreated, exposing a flat plain between the edge of the ocean and the upstanding Santa Monica Mountains. Stream erosion of the Hollywood Hills resulted in the accumulation of large Fan-shaped deposits of river sediment at the mouths of the canyons and extending out over the plain. Over the course of time, these alluvial fans extended farther from the mountains and raised the overall level of the plain.
Movement deep within the earth’s crust resulted in the formation of cracks, faults, and fissures that cut resulted in the formation of cracks, faults, and fissures that cut through the layers of gravel, sand, and mud laid down by streams and into the extensive natural reservoirs of the Salt Lake Oilfield. Crude oil seeped slowly upwards along these cracks until it reached the ground surface. At the surface the lighter petroleum portion evaporated, leaving behind shallow sticky pools of natural asphalt.
At Rancho La Bra, semi-solid asphalt oozes from the ground to create tar pits. The “tar pits” still visible in the park are the relicts of some of the more than 100 sites excavated for asphalt and for fossils.
Formed beneath the sea over millions of years, the crude oil began seeping through rock fissures after earthquakes raised California’s seabed 40,000 years ago.
Incredibly sticky, but with a deceiving layer of water, the pools acted like giant flypapers for animals.
La Brea’s pools have been fooling herbivores, carnivores and scavengers for millennia—those that entered the pools became trapped and suffocated in the deep glutinous deposits, entombing extinct species such as the giant ground-sloth, camel, tapir, mammoth, saber-toothed cat, mastodon, panther, sub-nosed bear and the dire wolf.
With literally millions of fossils excavated, La Brea is one of the best-known fossil communities in the world.
Geologists, paleontologists, and biologists seek to understand the climate and ecology of the past using many different types of information. By comparing ancient sediments with those being formed today, geologists are able to reconstruct the landscape of 40,000 years ago. By comparing the fossils with their nearest living relatives, biologists and paleontologists are able to understand more about ancient life. Differences between fossil animals and plants and their living representatives can tell us much about changes in climatic and environmental conditions at different times during the history of the earth.
We know from the La Brea Asphalt Pits that the local area during the Pleistocene climate was cooler and more humid, and the landscape was clothed by different kinds of vegetation and inhabited by some rather strange animals. In all some 140 species of plants and more than 420 species of animals, and small birds and rodents–are best known from the Rancho La Brea deposits.