Today, the La Brea Tar Pits, a public park and museum, lie between shopping centers and apartment buildings. But the sticky, black asphalt that fills the pits was oozing up from the ground long before ...

Within the sprawling metropolis of Los Angeles, not far from West Hollywood and Beverly Hills, paleontologists are hard at work sorting through one of the richest collections of ice age fossils in ...

Basically, what they are is a big much of petroleum and asphalt mixed with dirt and the like. Here is the wiki explanation: "The La Brea Tar Pits (or Rancho La Brea Tar Pits) are a famous cluster ...