During the last ice age, LA was a land of bubbling asphalt and roaming mammoths, mastodon, saber toothed cats, ground sloths, and other bizarre creatures. LA wasn't covered in ice, but it was about 10-15 degrees Fahrenheit cooler and 10% more humid than it is today. The asphalt trapped these big animals and their remains became part of a hardened matrix of soil, sand and other sediment. In the early twentieth century, after LA was settled by homesteaders, scientists began excavating the area and realized that the fossils weren't of modern animals (as was previously thought), but prehistoric, extinct animals.
Today, La Brea Tar Pits, in the middle of LA, is home to a fun and interactive museum. A standard field trip destination for the elementary and middle school set, little kids ooh and aah at the thirteen foot tall Columbian Mammoth and plug their noses as they walk past the tar-smelling quarry. Excavation continues onsite and scientists are still discovering new species.
From left: American Mastodon (baby and adult) and Yesterday's Camel