Bonny Doon Beach: Railroads and Oil

Bonny Doon Beach.
Dramatic sea cliffs of Santa Cruz Mudstone at Bonny Doon Beach. Photo: Julia Gaudinski/Mobile Ranger

California’s Bonny Doon Beach is home to wide-open sands, a creek that runs through it, and even a clothing-optional section to the right of the chunk of Santa Cruz Mudstone where there used to be a natural bridge. It is also has a few features that tell of the areas railroad and oil exploration history.

Aerial view of Bonny Doon Beach circa 1975 when there was still a natural bridge. Photo: From the collection of Paul and Carmen Mulholand via Tom Scully
Aerial view of Bonny Doon Beach circa 1975 when there was still a natural bridge. Photo: From the collection of Paul and Carmen Mulholand via Tom Scully
Doon Beach with its natural bridge  circa 1975. Photo: From the collection of Paul and Carmen Mulholand via Tom Scully
Doon Beach with its natural bridge circa 1975. Photo: From the collection of Paul and Carmen Mulholand via Tom Scully

Notice the Parking Lot

When you park to go to Bonny Doon Beach, the main parking area hugs right up to huge hill. It so happens this hill is a man-made embankment. The local stream used to run out to sea in the area where the embankment is now. If you have driven between Santa Cruz and Davenport, you might have wondered why you can’t see the ocean very often on the drive. It’s because every creek along the route has an earthen railroad berm or embankment across it that blocks the view. They were all built in the early 1900s, and the embankment at Bonny Doon Beach is a great example of a very big one.

The inland view of the earthen berm on which the railroad tracks sit. The two arrows show the limits of the native bedrock, i.e., the Santa Cruz Mudstone. In between the arrows is all fill for the embankment.
The inland view of the earthen berm on which the railroad tracks sit. The two arrows show the limits of the native bedrock formed from the Santa Cruz Mudstone. In between the arrows is all “fill” for the embankment. Image: Julia Gaudinski/Mobile Ranger

Grandiose Railroad Plans

At the turn of the 20th century, railroads were king and still expanding with easy money from business tycoons of the day. The railroad embankments we see today were originally part of the Ocean Shore Electric Railway, which was begun in 1905 and was to be a grand line from Santa Cruz to San Francisco. It was to have two parallel electric lines to run both passengers and freight and be completed in 1907. Southern Pacific was also building rail to Davenport at about the same time, so there was definitely some hardball and power politics between the two companies.

A More Humble Reality

Fate intervened. The 1906 quake caused huge damages to the northern end of the Ocean Shore line, and their easy funding largely dried up. Construction continued, although money had to be raised from local bonds. Southern Pacific secured the contract to transport cement and materials for the Davenport Cement Plant, and that took away much- needed revenue from Ocean Shore.

Construction of the Ocean Shore line circa 1905. Image from the collection of Alverda Orlando.
Construction of the Ocean Shore line circa 1905. Photo: Collection of Alverda Orlando

The details of how the collaboration ultimately occurred are hard to pin down, but Ocean Shore and Southern Pacific collaborated in building the embankments north to Davenport. The embankments are so wide because they were designed for three tracks (two for Ocean Shore and one for Southern Pacific). They consist of wooden trestles filled in with local material to enable the structures to support the extreme weight of the railway cars loaded with cement.

This 1906 photo shows the wooden railroad trestle that crosses San Vincente Creek, at Davenport, partially filled in. There are many of these filled trestles between Davenport and Santa Cruz, including the one at Bonny Doon Beach. Photo from the collection of Gary Griggs and courtesy of Sandy Lydon.
This 1906 photo shows the wooden railroad trestle that crosses San Vincente Creek, at Davenport, partially filled in. There are many of these filled trestles between Davenport and Santa Cruz, including the one at Bonny Doon Beach. Photo: Collection of Gary Griggs, courtesy of Sandy Lydon

By 1908, only portions of the rail on each end of the Ocean Shore line were running: Santa Cruz to Swanton, which is just north of Davenport, and San Francisco to Tunitas Creek, a few miles south of Half Moon Bay. The railroad never fully connected Santa Cruz to San Francisco. Ocean Shore stopped running trains by 1920 and never laid their second line. The Southern Pacific line was eventually sold to Union Pacific, which ran freight for the cement plant until the plant closed in 2010.

Why There Is a Tunnel

Creation of the railroad embankments meant completely blocking off the creeks and any associated estuaries and lagoons. Water flow was routed through tunnels made through the Santa Cruz Mudstone. The tunnels are on the north side of each beach and, despite large storms, have eroded little and have been adequate to handle the flow. In the picture below, the black arrow points to a tunnel where Liddell Creek comes out of the Santa Cruz Mudstone. You can follow the water to its exit at the ocean. The black rectangle shows the very linear railroad embankment that now defines the back of the beach.

An aerial view of Bonny Doon Beach. The black rectangle encompasses the embankment made by the filled railroad trestle. The arrow on the left points to the tunnel through which Lidell Creek drains to the sea. Picture © Kenneth and Gabrielle Adelman, California Coastal Records Project www.Californiacoastline.org
An aerial view of Bonny Doon Beach. The black rectangle encompasses the embankment made by the filled railroad trestle. The arrow on the left points to the tunnel through which Liddell Creek drains to the sea. Photo: © Kenneth and Gabrielle Adelman, California Coastal Records Project, http://www.Californiacoastline.org
Liddel Creek draining through the man-made tunnel (drilled in 1907/1908) in the Santa Cruz Mudstone
Liddell Creek draining through the man-made tunnel, which was drilled in 1907-1908 through the Santa Cruz Mudstone. Photo: Julia Gaudinski/Mobile Ranger

There’s Oil in Them Thar Hills!

In the farthest-right cove at Bonny Doon Beach (yes, the clothing-optional section), a tall skinny dike of sandstone cuts across the Santa Cruz Mudstone. A dike is essentially loose material. In this case, it’s the older and deeper Santa Margarita Sandstone, which was squirted up under pressure through the younger but harder mudstone. The dikes and the Santa Margarita Sandstone contain bituminous (asphalt-like) material in varying quantities. There are many similar dikes in the sea cliffs along the north coast of Santa Cruz. This one is unusual in how skinny and rectangular it is.

A sandstone dike that cuts across the Santa Cruz Mudstone. The blue line parallels the dike just above it.
A sandstone dike that cuts across the Santa Cruz Mudstone. The blue line parallels the dike just above it. Photo: Julia Gaudinski/Mobile Ranger

Some of the bituminous sandstones just a few miles south, at Majors Creek, were quarried for paving material. Apparently, about 600,000 tons, valued at more than US $2 million, were quarried and sent by boat to pave San Francisco between 1888 and 1914. In the 1950s, the Husky Oil Company ran an experimental project to extract oil and gas by heating the sandstone in the drill hole and then recovering what melted. Over three years, they pulled out 3,000 barrels of oil and some gas. But costs were too high, overall, to make it economically viable.

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  1. Sources Used

      • North Coast Railroad Ramparts. Sandy Lydon’s Central Coast Secrets website.
      • "The Geology from Santa Cruz to Point Año Nuevo—The San Gregorio Fault Zone and Pleistocene Marine Terraces," by Gerald Webber and Alan Allwardt, in Geology and Natural History of the San Francisco Bay Area: A Field-trip Guidebook: 2001. Fall Field Conference, National Association of Geology Teachers, Far Western Section, September 14-16, 2001. USGS Bulletin 2188, 2001:194.
      • Living with the Changing California Coast, by Gary B. Griggs, Kiki Patsch, and Lauret E. Savoy. University of California Press, 2005.




About The Author

I really enjoy field trips. I love being in a cool place and having someone tell me about it. The problem is, you can’t always find a professor or park ranger-type to tell you all they know about the local rocks, plants, and history. So I decided to combine my love of things natural with mobile technology.

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14 Comments

  1. Kevin creighton

    I drive tour bus since 1985. Had bus loads drop there from Stanford in the mid eighties. We’d drop at 830 and pick up around 1Am. Crazy stuff

    Reply

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