March 25, 2010

La Brea Tar Pits in Los Angeles

Today we decided to drive into Los Angeles to visit the La Brea Tar Pits. I remember my parents taking me when I was a little boy, but Linda had never been there (to her recollection). Because of our great interest in Pleistocene Megafauna and Hilina's great interest in any animals, it was a wonderful day.

Hilina went absolutely crazy in that museum, running around telling all the little kids (and some older ones) what the names of the animals were.

There was even a moment when she pushed her way to the front of a visiting elementary school class to announce that the woolly mammoth has lots of hair because it was so cold outside (she learned that when we saw one at the International Wildlife Museum in Tucson over a month ago and remembered.

We also toured the asphalt seeps around the complex. Because of how California was formed, by the accretion of oceanic islands and the crumpling of oceanic sediments by the compression of the San Andreas Fault, petroleum reserves under the ground have faults and dikes they can follow directly up to the surface.
There are seeps all over the compound. They are not dangerous to touch, in fact the excavators have the stuff all over their hands and bodies. But, it sure is sticky!

When crude oil makes it to the surface, the methane, kerosene, and other more volatile parts of it evaporate into the air, leaving behind a thick sticky goo called asphalt (technically tar is a compound left behind by the distillation of wood products). This asphalt is what trapped over 100,000 animals over the past 40,000 years.

It is the best preservation site in the world of Ice Age Megafauna. An amazing assortment of species went extinct between 13,000 and 6,000 years ago. This includes Saber-tooth cats, American lions, short-faced bears, Western horses, American camels, llamas, two species of giant bison, three species of ground sloth, dire wolves, four species of condors, multiple eagle and hawk species, giant storks among many others. Some 600+ species of animals have been found in the pits.

One of the biggest questions is, why did some species go extinct when their habitat remained. Horses, camels, and pigmy pronhorns? When horses and camels were brought to America from Europe/Africa they did quite well living in the wild. But, for reasons unknown, they went extinct.

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