Craig Lingle age 10, Seattle, Washington, , for his questions
What caused the La Brea tar pits?
The tar pits of Rancho la Brea come from underground petroleum
Petroleum comes from bitsy plants and sea creatures. This oily goo is processed through ages of time in the heat and pressure of the earths rocky crust. The ancient seas flooded and retreated from the land, Pockets of water, teeming with bits of life were left for burial across the continent; Different conditions processed the remains into different kinds of petroleum,
Pennsylvania oil has a paraffin bases Its solids gel into paraffin wax. Across the continent from east to west the petroleum has less paraffin and more naphtha. The solids in Texas and California oil are gooey dark pitch, Los Angeles, home of the La Brea tar pitsp is as far west as we go. Here the western oil oozes up to the surface. The light, volatile materials turn to gas in the air andjescape. The tar pits are~the solid residues that remain,
When California belonged to Mexico, the famous tar ranch was owned operated and named by the Spanish. Brea is their word for pLtch. The tar was sold as a paving material. Some 80 years ago, the ranch was owned by a Major Hancock who sold his tar for around $20 a ton. But he had a problem. The dark, sticky, tangy smelling stuff was full of bones. Hours of labor were spent sifting old teeth and bones from the tar before it could be marketed.
The major had a good idea of how the bones get into the tar pits. In the center, the tar was wet and soft, This is where the evaporating oil oozed up from below ground, The tar dried and hardened towards the edges of the overflow. Blowing dust stuck to it, making it look like the ground. Rain left puddles on the tar. The major had seen his farm animals mistake the shining pools for safe drinking water. The first few steps on the .outer rim were safe enough. Then came trouble, The thirsty animal was soon hopelessly stuck in the soft tar. Colts, calfs, ducks, sheep and hens had to be rescued or perish.
The major guessed that his tar pits had been trapping animals for a long time, Some of the bones puzzled him, especially a curved tooth nine and a half inches long. Imagine his surprise to learn that it belonged to a saber‑toothed tiger of the Ice Age.
Much later, the masses of bones were sorted and studied. Most of them belonged to very old or very young animals. The young were more likely to be fooled. The old were less able to free themselves when trapped. Most of the bones were from meat‑eating animals. This is because a horde of hungry flesh eaters would pounce on a grass‑eater trapped in the tar. All perished together in a sticky mass.
What a record was found of who's who in America of 100,000 years ago. There were tigers, lions, wolves, horses, camels, sloths, coyotes and even mammoth elephants:. Also present were the skulls and beaks of vultures who had swooped to feed on the struggling victims. Sorting was a great job. Tar preserves the bones but tends to scatter the skeletons. One cubic foot of tar from La Brea yielded the bones of 17 big animals ‑ wolves and saber toothed tigers.