Gas bubble slowly emerging at La Brea Tar Pits

The La Brea Tar Pits (or Rancho La Brea Tar Pits) are a cluster of tar pits around which Hancock Park was formed, in urban Los Angeles. Asphaltum or tar (brea in Spanish) has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with dust, leaves, or water. Over many centuries, animals that were trapped in the tar were preserved as bones. The George C. Page Museum is dedicated to researching the tar pits and displaying specimens from the animals that died there. The La Brea Tar Pits are now a registered National Natural Landmark.

• http://en.wikipedia.org/wiki/La Brea Tar Pits
• Page 38 - Dicka, A. B., 2012, 101 American Geo-sites you've gotta see: Mountain Press Publishing Co., 250p.