• Stars appear behind a dramatic landscape of rocky mountains, rolling hills, and fields of grass

    Santa Monica Mountains

    National Recreation Area California

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?

Sue Nelson, Jill Swift, and Margo Feurer were instrumental in the movement to create a national recreation area near Los Angeles.

Four state parks were the triumph of a grassroots movement to protect open spaces minutes from Los Angeles in the 1950s & 60s. Three women, Sue Nelson, Jill Swift, and Margo Feuer further galvanized the movement that helped make Santa Monica Mountains National Recreation Area a reality in 1978.