The Geology Rocks at Rodeo Beach South

Mill Valley, Ca – Need a secluded spot to relax? Check out Rodeo Beach South, a short hike through a beautiful landscape to a beautiful beach. Plus, it’s right near Point Bonita, making this an easy hiking double feature.

About the Park

Mill Valley, Ca – Region of the Golden Gate National Recreational Area

Science Spotlight: Rodeo Beach Geology

When I walk along California’s beaches, I tend to be so captivated by the landscapes around me that I find it easy to ignore the beauty beneath my feet. While every beach has some beautiful geological history to offer, Rodeo Beach stands unique amongst other beaches. Its beautiful, coarse, and pebble-dotted sands reflect a rich geological history.

Remember learning about the 3 major rock families when in elementary school science? As a refresher, rocks can be categorized based on the way in which they are formed. The three rock families are igneous, sedimentary, and metamorphic rock – and it just so happens that you can find all three on Rodeo Beach, making it a gem in terms of California geology.

Looking at the beach geology more granularly, one source reports that Rodeo Beach sands are composed of the following: red and green chert (about 55%), volcanic rock fragments such as pillow basalts (about 30%), lesser amounts of graywacke sandstone (about 10%) and finer mineral grain, such as feldspar and hornblende (about 5%).

Carnelian, although representing a small percentage of the rock composition, is another notable find on Rodeo Beach. These semi-precious gemstones are bright to reddish-orange in color. These beach gems are formed when small pockets, or vesicles, of silica appear within cooling lava. Years of collecting have negatively impacted the amount of carnelian found on Rodeo Beach, so be sure to refrain from collecting.

© David Abercrombie, 2014, Flickr Album, some rights reserved.

Visit the Park

Please note that there is no entrance fee to enter the park. Dogs are allowed on leashes.

We recommend visiting the southern tip of Rodeo Beach since it’s a skip, hop, and a jump away from Point Bonita. Regardless of the area that you visit, be sure to keep your eyes peeled for shorebirds dotting the beaches, mats of invasive ice plants, and the mosaic of different rocks that make up the sand.

Here are some helpful resources to help plan your visit:


Explore a Lighthouse at Point Bonita

Sausalito, Ca – A jewel of the North Bay, the Point Bonita Lighthouse rests as a beautiful and historic part of California. 

Sausalito, Ca – Region of Golden Gate National Recreational Area

About the Park

Science Spotlight: Invasive Ice Plants

When making the trek up to the Point Bonita Lighthouse, it’s hard to miss the dense carpets of dark green succulent. Introduced to California in the 1900’s to help control erosion, the South African-native ice plant is beginning to overstay its welcome. A common sight along California’s coastal areas, the ice plant has been deemed invasive on stretches of almost all of California’s coast.

Although it’s a decorative and beautiful flowering succulent, it’s causing major problems for the native California plants that it’s outcompeting. Once established, the ice plant forms dense mats which force out native plants and alter the soil composition.

Its root system is shallow, making localized control possible. However, the ice plant is so widespread that it’s unrealistic to tackle it all in one swoop. For more information on how you can help control the problem, check out this site which helps provide resources to volunteers.

Ice Plant.jpg
A carpet of Ice Plants; photo from Lighthouse Field State Beach.

Park History

The discovery of gold in 1848 transformed the San Francisco area – what was once a city of 900 people quickly grew to over 20,000. To meet the needs of a booming population, the area began construction of lighthouses around the bay to lead the way for settlers. Point Bonita, completed in 1855, was the third lighthouse on the west coast. It remains still in operation today as a part of the Golden Gate National Recreational Area.

Visit the Park

Please note that there is no entrance fee to enter the park. Dogs are not allowed.

Before visiting, please note that the lighthouse is only open for visiting Saturdays, Sundays and Mondays from 12:30 p.m. to 3:30 p.m, so plan accordingly.

Point Bonita Lighthouse is a 1 mile, out-and-back trail that winds around beautiful coastline to the lighthouse. During your visit, be sure to enter the lighthouse.

Here are some helpful resources to help plan your visit:



Watch Elk and Gray Whales at Point Reyes National Seashore

Inverness, Ca – Ever hear of a place where you can see migrating gray whales and a common murre colony, all while climbing down a dramatic 308-step staircase to a lighthouse? Here we have the Point Reyes Lighthouse in a nutshell.

Species to Look Out For

Common murre circle

Common Murre

About the Park

Inverness, Ca – National Seashore

Science Spotlight: Common Murres at Point Reyes

Point Reyes National Seashore has recorded nearly 490 species of birds – over 50% of the birds found in North America. This makes the area the most species-diverse park in America’s National Park System.

When hiking down to the Point Reyes Lighthouse, Dan and I caught a whiff of a smell on the breeze that brought me back to my summers spent monitoring nesting herring gulls. The smell was distinctively… seabird. Naturally, this piqued my interest. We stopped for a moment at one of the lookout sites, and within minutes found a colony of common murres in the distance.

Common murres are the most abundant nesting seabird found off the coast of north and central California, and several colonies make their home at Point Reyes National Seashore. In the mid-1980’s, the common murre suffered a severe population decline due to entanglement in fishing nets and the culmination of several oil spills along California’s central coast. Murre restoration projects have brought rising numbers and hope to the species populations, but they remain threatened by the consequences of a changing climate.

© 2010,Allen Shimada, NOAA Photo Library (Flickr), some rights reserved.

Park History

The Coast Miwok Native Americans occupied the area that we know now as Point Reyes for thousands of years. The first known European explorer to visit the area was Sir Francis Drake, who arrived to Point Reyes in 1579.

The Point Reyes Lighthouse, constructed in 1870, rests at the second foggiest place in North America. The lighthouse was replaced with an automated light in 1975, but it still remains as a museum piece with the National Park Service.

Visit the Park

Please note that there is no entrance fee to enter the park. Dogs are allowed on leashes.

With a total of 71,028 acres of protected land, you’ll certainly take a long time to run out of places to explore at Point Reyes. The Tule elk, a subspecies of elk only found in California, can sometimes be seen on the sides of roads or on grassy hillsides. We recommend completing the 1+ mile hike down to the Point Reyes Lighthouse, which offers seasonal views of common murres and gray whales. That said, anywhere you go will be rich in wildlife and scenic views.

Please note that during whale watching season (late December to mid-April), the main road to the lighthouse is closed to private vehicles. Be sure to check the shuttle information if you plan on visiting during that time.

Here are some helpful resources to plan your visit: