The City of Laguna Hills has been built over unusually rich deposits of fossil-bearing sediments. These strata represent over 17 million years of prehistory from marine incursions to coastal emergence and the formation of today’s hills and valleys.
The oldest environment was a subtropical embayment with a mountain peninsula to the southwest and a rolling plain to the northeast. Fossils from this time are exposed today in Fossil Reef Park, just west of the Laguna Hills Community Center and Sports Complex.
The shore slowly sank to become a wide seaway in which fossil plankton and whalebones accumulated. Volcanic activity flanked the subsiding shores. These deep-sea sediments extend under Laguna Hills High School and the City of Laguna Woods.
When the sea floor began to rise, the emerging shore became the home to primitive sea lions, shore birds, and abundant mollusks. Fossils of these animals have been collected from the sand and silts of Nellie Gail Ranch.
Tectonic activity continued to lift the landscape through the Ice Ages and by 1 million years ago, the Santa Ana Mountains had begun to form. Mammoths, Mastodonts, and Saber-Toothed Cats roamed the savannas and stream channels of Saddleback Valley. Their teeth and bone fossils were found during the construction of Costeau Park and the Community Center.
The Community Center murals illustrate the prehistory of the City of Laguna Hills changing landscapes. These are represented by a shallow tropical embayment, an open sea, and Ice Age grasslands. The remains of the diverse life that inhabited these paleo-environments are displayed throughout the foyer for public enjoyment and education.