Posted by: James Wapotich | March 21, 2016

Trail Quest: Haskell’s Beach Geology Walk with Susie Bartz

Like a number of our local beaches Haskell’s provides a great opportunity to learn about the geology of our area. 

The beach is near the estuary of Tecolote Creek and as one hikes up or down the coast the beach becomes sheltered by high bluffs providing an opportunity to study both the rocks and how they were formed.

Haskell’s Beach is accessible from Hollister Avenue, just east of Bacara Resort. From the coastal access parking area a short interpretive trail through restored native plants leads down to the beach.

Eagle Canyon Haskell's Beach geology monterey shale Susie Bartz hike walk

Eroded Monterey Shale is seen near Eagle Canyon

Recently, as part of a series of four geology walks hosted by Santa Barbara Botanic Garden, Susie Bartz led a guided walk along the beach during a minus tide towards Eagle Canyon, which is about a mile west from Haskell’s Beach.

Ms. Bartz began by describing how the rocks we see today got to be where they are, and how their history is tied to that of the San Andreas Fault and the movement of two tectonic plates. The fault was created around 20 million years ago when the Pacific Plate began grinding alongside the North American Plate, moving northward along the fault line. In the process, the Pacific Plate took a good size piece of the North American Plate with it, essentially Baja California and everything west of the San Andreas Fault up to the San Francisco Bay area.

Starting around 18 million years ago, through this same movement, a smaller piece of crustal block, that was originally down where San Diego is now, was dragged up the coast and rotated 90 degrees before being driven back into the rest of the land mass. This block became the Western Transverse Ranges, and is also the reason why it our local mountains are oriented east-west. 

About 6-7 million years ago there was enough compression and uplift to bring what is now the Santa Ynez Mountains above the water, lifting sedimentary rock that had been formed on the sea floor over millions of years to where it is now.   

Haskell's Beach geology ash Susie Bartz Santa Barbara Botanic Garden hike walk goleta

Susie pointing out weathered volcanic ash seen in Monterey Shale

This same ongoing compression and uplift also tilted the sedimentary rock, which was originally flat, up on end, such that the layers are now at an angle. In fact, as you move from the coast up into the mountains you’re progressively moving across older and older rock formations until you reach to the top of the Santa Ynez Mountains. Along the bluffs at Haskell’s, the youngest of these sedimentary rocks is the Monterey Formation. 

The first stop along the walk was Goleta Historical Marker 3, located just past the restrooms. In 1942, a Japanese submarine fired on the Elwood oil installation above where Haskell’s Beach is now. Oil was first discovered in the Elwood field in the late 1920s and the attack underscored the strategic importance of the site. The event also indirectly highlights our ongoing relationship with Monterey Shale. 

Continuing down the coast the group stopped at the first visible out cropping of Monterey Shale, which is the source of the oil. The tan-colored sedimentary rock was formed underwater between 18-6 million years ago.  

“As mud and sand are washed down from the land they find their way out from the beach. The sand pretty much drops out in the surf and tidal zone. The mud finds its way further out to where the water is a lot quieter and all the tiny mud or clay grains fall to the ocean floor.” Ms. Bartz told the News-Press. “As time goes on, all of these various sediments get buried under more and more layers and eventually hardened into rock.” 

Monterey Shale is a mudstone or claystone formed through this process. The same time that these layers were being built up, microscopic phytoplankton and zooplankton such as diatoms and foraminifera were living in the ocean. When these organisms died, their bodies settled on the ocean floor in the soft mud and became part of Monterey Shale. 

While this was happening, the sea floor was already experiencing the ongoing effects of tectonic compression, which was causing folds and wrinkles in the underlying rock, creating a rolling surface of troughs and rises. And in the deeper troughs, where there was very little oxygen, the decomposing organic matter collected and slowly turned into oil and gas.

Over time as more sediment was deposited and the layers hardened, the oil and gas, being less dense than water, slowly migrated upward, where it often met an impervious stone layer. Here, in the rises, or anticlines, of the folded layers the oil collected forming reservoirs, many of which are being now drilled into today. In fact, as Ms. Bartz pointed out, Platform Holly, which is visible from Haskell’s Beach, sits above of one of these anticlines, tapping into the oil that is trapped there. Where the oil is able to freely reach the surface, it congeals and washes ashore forming the tar we find along our beaches.

marine mammal fossils haskell's beach Susie Bartz Santa Barbara botanic garden walk hike goleta

Fossilized marine mammal bones seen along the walk

Near Venoco Pier, the group stopped to look for fossils of marine mammals. While most of the fossils in Monterey Shale are microscopic, deep water marine mammals such as dolphins, porpoises, and whales that died and sank to the ocean floor also became part of the formation. To help participants recognize fossilized bone, Ms. Bartz brought a cross section of a modern bone showing the “spongy” looking marrow inside, which can also be seen in fossilized bones. 

Midway between the pier and Eagle Canyon, Ms. Bartz pointed out a section of Monterey Shale that looked unusually weathered. Here, part of the formation appeared almost rusted, and disintegrated much more easily than the surrounding rock layers. This weathered layer was caused by volcanic ash that had been deposited millions of years ago while the Monterey Shale was being formed underwater.

Through radiometric dating, geologists are able to use these relatively thin layers of volcanic ash to determine the age of the surrounding rock; and through chemical analysis, they can determine where the ash came from. During the Miocene epoch, when Monterey Shale was formed, there were a number of active volcanoes in our area – Tranquillon Mountain, south of Lompoc; Morro Rock and the Nine Sisters in what is now San Luis Obispo County; the Santa Monica Mountains; and further inland in the Mojave desert. 

On the return hike, Ms. Bartz led the group in exploring tide pools exposed by the minus tide. Some of the animals found along the walk included mussels, gooseneck barnacles, chitons, limpets, sandcastle worms, and giant limpets, many of which were also found on the pilings supporting Venoco Pier.

Ms. Bartz’s interest in geology solidified after she moved to Santa Barbara in the mid-1970s. “I’ve always been interested in what’s under my feet, even as a child growing up in Pennsylvania, but driving west across the country for the first time was a real eye-opener because I could see the landscape over a great distance.” Ms. Bartz reflected. ”After that, I wanted to understand the geology of what I was hiking over.” This led her to taking the full curriculum of geology classes at Santa Barbara City College and earning a degree in geology. 

In the late 1990’s, she met renowned geologist Thomas Dibblee, Jr. After his death in 2004, she helped edit his geologic maps at the Santa Barbara Museum of Natural History, bringing them to final publication.

Haskell's Beach Geology walk Santa Barbara Botanic Graden Goleta

The group making its way down the beach during low tide

A firm believer that we need to get back into physical connection with the earth and the natural world around us, Ms. Bartz began leading natural history walks in the mid-1990s. 

“We are very much drawn into media. Our children, for example, are learning at a very young age how to find information about our earth on computers. And while it’s important to know how to access that information, to complete the picture it really requires going outside and actually experiencing the landscape,” Ms. Bartz shared. 

Two more upcoming geology walks are being offered through Santa Barbara Botanic Garden. On April 2, Ms. Bartz will lead a walk to Inspiration Point and on April 20, she’ll lead another at La Cumbre Peak. In October, she will also be leading a walk for the Botanic Garden along the Santa Ynez River at Red Rock. For more information about these upcoming walks go to, http://www.sbbg.org. 

This article originally appeared in section A of the March 14th, 2016 edition of Santa Barbara News-Press.


Responses

  1. Will there be a Haskell’s beach geology walk in 2017?


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