• Afternoon clouds cover the distance peaks of the iconic Boney Mountain

    Santa Monica Mountains

    National Recreation Area California

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  • Partial Park Closure Due to Hazardous Conditions

    Rancho Sierra Vista/Satwiwa re-opens 5/14/13, with restrictions (sunrise to sunset, not all trails). Sandstone Peak & Mishe Mokwa trails will also open, as will Backbone Trail east of Point Mugu State Park boundary. Point Mugu backcountry remains closed. More »

  • Trucks on Cheeseboro Canyon Trail

    Occasional truck traffic (approx 6 trips per day) will take place on Cheeseboro Cyn Trail weekdays between 8am & 4pm for demolition and removal of Cheeseboro Tank. Should be completed by 5/24/13. Check back for updates or call 818-889-8996. More »

Geologic Formations

Looking from Circle X Ranch, one can see the Channel Islands which formed at the same time as the Santa Monica Mountains.

Imagine standing on the shores of Malibu 24 million years ago. The dinosaurs are long gone, but the Santa Monica Mountains are yet to be born. Broad plains extend from the middle of California to the coast. Much of the land that makes up the Los Angeles area is underwater.

For millions of years, the ground slowly moves, churns, and presses until the Earth begins to crack and molten lava oozes from underwater vents. Thus, only about 16 million years ago, the Santa Monica Mountains and Channel Islands began to glimmer in the ocean depths.

In time, the eruptions became explosive and burst through the water’s surface. For another 3 million years, the mountains continued to grow to over 10,000 feet high. Three times taller than they are now!

 
This is a fossil imprint from a ancient clam that lived in this area over 20 million years ago.

The Santa Monica Mountains that we know today are a complex and dynamic place that includes active fault lines, fossils, remnants of volcanoes, and even formations created underwater now at the top of ridgelines.

Click the links above to learn how various forces and the elements of time have peeled away the layers creating the beaches, valleys, and landscapes we see today.

You can also download a map of the Geology of the Santa Monica Mountains (2 MB PDF)

 
This geology map of the Santa Monica Mountains was designed so that people with the most common types of color blindness can see the geology units.
This geology map of the Santa Monica Mountains was designed so that people with the most common types of color blindness can see the various geology units. Therefore, standard geology colors do not apply.

Did You Know?

The city of Los Angeles can be seen from many scenic view points in the Santa Monica Mountains.

Comprising 153,075 acres, Santa Monica Mountains National Recreation Area is the world's largest urban national park. It has more area codes (5) and zip codes (26), including the notable 90210 zip code of Beverly Hills, than any other unit in the National Park System.