Rock Record: Panther Beach, an Extraordinary Geologic Feature in Santa Cruz

Written by Gavin Piccione

One of the most exciting perks of having an appreciation for geology is the limitless possibility to find new geologic features, even on the most seemingly mundane trips outside. It may be an interesting pebble that catches your eye or a new outcrop that piques your interest, but one usually does not have to travel far to find thought-provoking rocks. However, within this vast collection of terrestrial curiosities, some features stand out as particularly exceptional or interesting.

On a recent trip to Panther Beach, I experienced the thrill of discovering one of these remarkable geologic marvels hiding just up the coast. In this installation of Rock Record, I cover why the rocks at Panther Beach in Santa Cruz are a world-renowned sedimentary outcrop, and I investigate how this truly unique part of the cliff was deposited here.

The Rocks at Panther Beach

At first glance the rocks at Panther beach may look very familiar to folks who have spent time in Santa Cruz, with cliff walls of the main section of beach made up of the crumbly, beige sedimentary rock called Santa Cruz mudstone. However, if you head to the south-end of the beach, and pass under the archway, the rocks change drastically. Instead of the highly uniform mudstone, the rocks on this side are wavy, laminated sandstones (see image 1). Below these peculiar sandstones there are darker rocks, called dolomite-cemented sands, that have bands that tilt down and towards the southeast. If one breaks or scratches these dolomite-cemented sands, they may smell the faint odor of petroleum. The contact between these two rock types is high irregular, looking almost as if the dolomite-cemented sands were bubbled up into the wavy sandstones like liquid in a lava lamp (see images 2 and 3). Capping these two sandstones is the familiar Santa Cruz mudstone that makes up the rest of the cliff (see full outcrop in image 4).

Image 1: Wavy sandstone at Panther Beach
Image 2: Contact between the wavy sandstone, and the dolomite-cemented sandstone. Image from Sherry, et al. 2012
Image 3: Contact between the wavy sandstone, and the dolomite-cemented sandstone. Image from Sherry, et al. 2012
Image 4: Panther Beach outcrop. Image modified from Sherry et al. 2012

Formation of the Panther Beach Outcrop: The World’s Largest Sedimentary Injection Deposit

When geologists see large sections of rock that are unrelated to the surrounding rock, we often think of some surface process like motion along a fault, that may bring two different rock types in contact. However, at Panther Beach there is no evidence for a fault that could have brought the sandstones to the surface. So how did this ~100m section of sandstone become emplaced in a cliff that is otherwise made of Santa Cruz mudstone?

To understand the formation of the Panther beach outcrop we must start about 1 kilometer below the seafloor. Around 9 million years ago off the coast of ancient Santa Cruz, 1000 meters of mud (the Santa Cruz mudstone) was deposited at the bottom of the ocean above a thick sand deposit (the Santa Margarita sandstone). Later, after heat, and pressure turned most of these sediments into rock, the only sediments left were small pockets of Santa Margarita sands that had not been lithified (i.e., turned to rock). Portions of these sand pockets were rich in oil, which created two distinct reservoirs: oil-rich sands and oil-poor sands. These two sand types were spatially separated because of the density difference between oil and water (see image 5).

Image 5: Sediments prior to injection. Schematic modified from Sherry, et al. 2012.

As more mud was deposited atop the Santa Margarita Sands, the pressure on the sand built. Then finally a geologic event, probably either an earthquake or a landslide, shook the sediments causing the slurry of both oil-rich and oil-poor sands to be injected, at a high velocity, into the overlying rock through fractures in the Santa Cruz mudstone. This type of formation is called a sediment injection deposit, where sediments from below are squeezed up into the overlying strata like a tube of toothpaste (see image 6). While the sands were injected, the oil-rich sand slurry would have traveled slower than the oil-poor sands, leaving the oil rich sands below the oil-poor sands. Injection deposits occur in other places on Earth, but the Panther Beach outcrop is the largest sedimentary injection deposit in the world!

Image 6: Sediments after injection. Schematic modified from Sherry, et al. 2012.

Getting to the Panther Beach Outcrop

Image 7: View looking towards the south through the archway in the cliff

Panther Beach is located off Highway 1 about 5 miles north of Santa Cruz. The parking lot for beach access is unmarked but can be found on google maps. The walk to the beach is about 50 yards down a narrow, steep trail (see the image at the start of this post for the view from the top of the trail). Once on the beach, turn left and walk under the arch in the cliff (see image 7). Be careful, this passageway may not be accessible at high tide, use caution when walking through and do not try to pass when water is high! The sedimentary injection deposit makes up the sea cliff beyond the south side of the arch.

The GPS coordinates for Panther Beach are: 36.994, -122.169


Much of the information for this edition of Rock Record was first published in the journal article: Emplacement and dewatering of the world’s largest exposed sand injectite complex, by Timothy Sherry and others.

Reference cited:

Sherry, T. J., Rowe, C. D., Kirkpatrick, J. D. & Brodsky, E. E. Emplacement and dewatering of the world’s largest exposed sand injectite complex. Geochemistry, Geophys. Geosystems 13, 1–17 (2012).

A Guide to the Rocks of Santa Cruz County

Santa Cruz is an area of geologic interest with a complex history of processes that shaped the coastline, bluffs, terraces, and mountains we see today! Wind, waves, earthquakes, fires, and other natural forces have changed and shaped the landscape for millions of years, though humans have only been able to document those changes in the recent past.

Jump To: Formations | Rock Types | Minerals | Resources


Geologic Formations

The above map shows the distribution of different rocks in Santa Cruz County. Each color represents a different kind of rock and, in turn, a particular age. Many of these rocks represent formations.

A geological formation is a basic rock unit that geologists use to group rock layers. Each formation must be distinct enough for geologists to tell it apart from surrounding layers and identify it on a map. A formation can consist of a variety of related or layered rocks, rather than a single rock type. There are over 14 geologic formations in Santa Cruz County. Most of these formations were created through movement of the crust because of tectonic uplift at the subduction zone off the California coast.

Most of the county is underlain by granitic rock. It formed about 100 million years ago from molten rock which cooled very slowly at a depth several miles below the earth’s surface. Since then, this area has been covered by the sea much of the time. Sand, mud and other sediment was deposited on the seafloor and was eventually compressed and hardened into sedimentary rock which was uplifted to form the Santa Cruz Mountains. Many of the sedimentary beds, which were originally horizontal, have been tilted, folded or partly eroded away. In some areas major faults have offset the rocks.

A large fossil in grey rock on the beach.

3 formations are known for fossils in this region:
Purisima Formation (3-7 Ma)
Santa Cruz Mudstone (7-9 Ma)
Santa Margarita Formation (10-12 Ma)

Learn more in our Fossil Guide.

Rock Types of Santa Cruz County

The three basic types of rocks — igneous, metamorphic and sedimentary — occur in Santa Cruz County. All are composed of minerals. Some consist of primarily one mineral, as in the case of marble, while others are an aggregate of many different minerals, as in the case of granite and conglomerate. 

Each rock type in the Santa Cruz area represents a different chapter in this region’s geologic past, and each has its own unique story to tell. The rocks of this area are mostly covered by soil and vegetation, so geologists must rely on scattered outcrops in creek beds, quarries, road cuts and sea cliffs in order to piece together the geologic history. 

Granite, Empire Grade Road

Igneous rocks formed from molten rock called magma. Plutonic rocks, such as granite, gabbro and alaskite, cooled very slowly, solidifying deep below the earth’s surface. This provided time for larger crystals of quartz, feldspar, mica and other minerals to form, giving the rocks a coarse texture. Volcanic rocks, such as basalt, cooled quickly at the earth’s surface and are very fine grained.

Marble, UCSC Quarry

The metamorphic rocks of this area are a geological enigma. They predate the granite rocks and were originally sedimentary rocks such as limestone, shale and sandstone. These were respectively metamorphosed into marble, schist and quartzite by the intrusion of magma about 100 million years ago. How much earlier these rocks were laid down as sediment, however, remains a mystery.

Mudstone, HWY 1 North of Santa Cruz

Sedimentary rocks in the Santa Cruz area originated for the most part from sediment such as mud, sand and gravel that was deposited on the sea floor. Over millions of years chemical alteration and pressure from burial hardened the sediment into rock. These rocks overlie the igneous and metamorphic rocks of this region and are of a younger age. 

Minerals

Minerals are the naturally occurring crystalline substances that make up the rocks around us. Minerals such as quartz, feldspar, and calcite are the most common constituents of rocks in this area. Dozens of other mineral species occur here, but in small amounts. Large, well-formed crystals- the kind most sought after by collectors- are scarce. 

Several minerals in this region have proven to be of great economic importance. Cinnabar (the chief ore of mercury) has been mined extensively at the New Almaden on the east slope of the Santa Cruz Mountains. Calcite (in the form of marble) has long been quarried near Santa Cruz for the manufacturing of lime and cement. 

Benitoite is the California state mineral. This unusual blue crystal was first discovered in 1907 in San Benito County. While benitoite is found in a few places around the world, San Benito County is the only place in the world where gem quality benitoite crystals are found.

Learn more in our Collections Close-Up.

Resources

Explore other resources for better understanding geology, paleontology, and the landscape of the Santa Cruz region.

Explore Online Rock Resources

Books and Papers

Geology at the Museum

On exhibit at the Museum

  • Specimens of common minerals from the region
  • Specimens of common rocks from the region
  • A detailed topographic geologic map of the county
  • Garden: Take a stroll around the Museum’s Garden Learning Center and see if you can spot fossils and other large rock samples.
  • Activities for kids: Multiple dig boxes features Santa Margarita Formation fossils of sand dollars and casts of a fossil sea cow.

Bring rocks home

Rent a kit to explore local rocks at home. Kit rentals are $10 per week and can be requested here (you do not need to be a teacher to request a rental).

Shop the geology and paleontology section of our online store

Santa Cruz Top 5 Geologic Must-Sees

Santa Cruz is an area of geologic interest with a complex history of processes that shaped the coastline, bluffs, terraces, and mountains we see today! Use this map as you walk, bike or ride your way across the county and explore some of the geologic must-sees our area has to offer. Visit our online Guide to the Rocks of Santa Cruz County to dig even deeper into the geology of the region.

Hiking With A Purpose: Post-fire community science with Josie Lesage

After fire, ecosystems can experience many changes. There can be increased risk of erosion and novel species can invade new areas, but fire can also reveal plants that have been waiting years for this natural disturbance to stimulate their seed banks — and there is still much to learn.

As the Santa Cruz community recovers from the impacts of the CZU Lightning Complex fires, we can look to other communities for guidance on where to go from here and how community scientists can help.

Join us for an online presentation from Josie Lesage of the Santa Barbara Botanic Garden and learn about their response to the Thomas Fire that burned through Santa Barbara and Ventura Counties in 2017-2018.

About the Mapping Recovery Project

The Mapping Recovery project leveraged the enthusiasm of over 100 volunteers who surveyed plants and erosion in the Thomas and Whittier fire scars. The project gathered over 5000 data points on the locations of plants in these fire scars, significantly expanding the known locations of many common invasive species, while also identifying populations of some rare or new invasive species. This data is being used to develop a map of priority intervention areas where restoration of native habitat is most needed and will be most beneficial to the ecosystem in the future.

About the Speaker

Josie Lesage works to understand, protect, and restore California habitats using ecological theory as a guide. She has a Ph.D. in Environmental Studies from the University of California, Santa Cruz, where she studied long-term management and community change in California’s coastal prairies. As the Santa Barbara Botanic Garden’s Applied Ecologist, she is interested in understanding how local ecosystems respond to disturbance and restoration intervention, and in building a community of volunteer scientists to steward our local habitats. She is currently involved in several projects related to invasive plant management and ecosystem recovery following fire. Her favorite plants are in the genus Castilleja


Interested in becoming a community scientist? Join us for an iNaturalist training in the Museum’s Garden Learning Center on September 11.

Collections Close-Up: Humphrey Pilkington, First California State Park Warden

Historic photo of Humphrey Pilkington in a camp site

August is an anniversary month for us here at the Museum, a time when we commemorate the establishment of the Hecox collection as the first public museum in Santa Cruz. In Laura’s story of coastal collecting and public exhibition, we find inspiration for our ongoing mission of connecting people to the natural world. However, this August, coming up on the one year anniversary of the devastating CZU Lighting Complex fires, we reflect on a different collector. In the story of Humphrey Pilkington, we trace a history of not only connecting to the natural world, but to a community fighting to protect it.

As many folks know, today’s Seabright was shaped, in part, by various members of the Pilkington family. From Thomas Pilkington, who developed beachfront Seabright into summer spot Camp Alhambra in the 1880s, to Thomas’ son James who built the first bathhouse at Castle Beach, to James’ brother T.B. who subdivided the family property, naming Pilkington Avenue in the process. But it is Thomas’ nephew Humphrey whose legacy secured the Museum’s home here in Seabright.

John Humphrey Blakey Pilkington was born in Illinois around 1858, emigrating to Santa Cruz with his parents in 1871. As a young man Humphrey studied agriculture at the University of California — knowledge he would put to work on his family’s orchards above what is now Delaveaga Park. His love for the landscape was not restricted to agriculture. Humphrey was well known for organizing walks from Watsonville through the mountains to San Jose, leading vacationers on tours of Yosemite, and co-hosting an annual picnic under the canopies of the beloved Big Trees.

The turn of the 18th century was an invigorating time for lovers of the local redwood forests — an 1899 fire galvanized community commitment to conservation, with folks like writer Josephine McCracken and photographer Andrew P. Hill pooling their talents to advocate for preservation of old growth redwood trees. The founding of the Sempervirens Club and the support their members drummed up were critical to the birth of California Redwoods State Park in 1902.

In July of 1903, Humphrey Pilkington started as warden of the park, whose name was not officially changed to Big Basin until 1927. Local papers praised this choice, including the Santa Cruz Evening Sentinel, which noted in April 1903 that “The people of Santa Cruz county take a pardonable pride in everything that pertains to [Big Basin] and they are naturally interested in seeing its management placed in the hands of careful, conscientious and competent men.” 

In addition to his work as an orchardist and forester, as well as various civic posts, Pilkington brought to the table years of voluntary service for the Santa Cruz Fire Department. These were fortunate skills to have in an unfortunate time — in September 1904, another fire swept through the mountains. Burning for 20 days, this fire proved famously stubborn, even reigniting into the following year. Impacting more than 3,000 acres of the park, the fire fueled fear and heartbreak even amongst those whose homes and lives were not in direct danger.

In the midst of the fight, Warden Pilkington did not change his clothes or sit down to a meal for nine days. Composed of up to 100 volunteers, firefighting crews focused their efforts on Governor’s Camp. This set of buildings was originally built to share the wonder of the Big Basin area with visiting California governors, in order to inspire government support for the park. They were ultimately successful, and these park buildings would later be developed into structures like the Campfire bowl, featured on this popular postcard. Last year’s CZU Lightning Complex fires echoed this historic fire, but with more intensity, given the current climate. The CZU fires burned through 97% of the park, sparing none of the contemporary structures that enhanced park access, which now must be reimagined.

Despite his widely praised management of the park, Pilkington was replaced as Warden in 1907 for political reasons. Ironically, while Pilkington had heroically fought the 1904 fire as the first warden of a California state park, his successor Sam Rambo would be found complicit in schemes to remove living trees under the guise of cleaning up damage from the 1904, and was the first state park warden to be fired in disgrace.

Pilkington’s departure from guardianship of the park did not extinguish his interest in nature, and he continued to be a student and collector of natural history. However, the collection he bequeathed to the City of Santa Cruz upon his death consists mostly of Indigenous stone tools and baskets. He developed his collection at a time when many EuroAmerican collectors were engaged in obtaining objects made by Native Americans under the racist impression that they were primitive peoples on the verge of extinction. For a bigger discussion of these collecting traditions and how they shape today’s museum collections, check out our November 2020 blog on Made for Sale Baskets.

Big Basin Campfire Bowl postcard, mailed in 1942. (From the Museum’s collection)

This collection was integral to the formation of our Museum here in Seabright. Pilkington’s gift was conditional upon the establishment of a formal museum, and the community rallied around the formation of a Museum that combined the Hecox collection and others under one roof where they could be better cared for.

As we reflect this August, we are saddened by the ongoing losses from the CZU fire, both personal and communal. We are interested in educating ourselves about the changing landscape. And most of all, we are encouraged to see the community rally around each other and their environment, from ongoing fundraising efforts for those impacted by CZU, to the reimagining of Big Basin, to our community science project on the impact of the fires on the natural world.  For more resource on fire preparedness, recovery, and ecological understanding, check out our upcoming CZU and You program series. 

Written by Kathleen Aston, Collections Manager, 2021


The Collections Close-Up is a series of blogs, events, and pop-up exhibits that highlight our collections.

On the Rocks: The Paleontologist’s Paradise

A layered cocktail in a highball glass

This month join us in raising a glass to the field of paleontology (the study of fossils) as we explore geologic time through a layered drink in one of our favorite glasses.

The history of life on earth is measured in millions of years, and humans are only a tiny blip in that long history. While geologic time can be a hard concept to wrap your mind around, people like Aristotle (384–322 BCE) first noticed the presence of fossil shells on land and concluded that the shape of the earth’s surface must have changed over time. Early scholars from across the world also made observations about the layering of rocks, and in 1669 the Danish scholar Steno proposed the Law of Superposition, a key concept to the earth sciences which generally states that stratigraphic layers on the bottom of a sequence will be older than those layered on top of them.

These concepts were the building blocks for the geologic time scale as we know it today. The geologic time scale is broken down into four large eons and each eon is then further broken down into eras, which are in turn divided into periods, epochs and ages. Today, we are living in the Holocene Epoch, going back 11,700 years ago it generally marks the end of the last ice age. The Holocene is also referred to as the Anthropogene, the “Age of Man” as of all recorded human history falls in this time period and it acknowledges the huge impact we have had on the earth.

Explore more about geologic time with videos from our Geology Gents and peruse our Guide to Local Fossil if you want to dig even deeper.

Layered drinks such as this one are both eye-catching and a fun way to experiment with the density of liquids. The force of buoyancy keeps the various layers from mixing as long as you are using liquids with different densities and build your drink with the heavier liquids at the bottom. Explore this resource for the relative densities of various liqueurs for your future cocktail creations.

Ingredients

0.5 oz. Grenadine or other syrup of your choice
1.5 oz. Coconut rum
1 oz. Dark rum
0.5 c. Juice (pineapple or other tropical flavor)
Ice

Recipe

  1. Pour the grenadine into the bottom of your glass.
  2. Fill the glass to the top with ice, trying not to splash the grenadine.
  3. Mix your juice with the coconut rum. Slowly pour over the ice so that the force doesn’t cause it to mix with the grenadine.
  4. Top with carefully poured dark rum.
  5. Garnish with the citrus of your choice.

Alternatives

  1. Substitute the dark rum for blue curacao for a more eye-catching color combination.
  2. For a non-alcoholic option, leave out the rum and experiment with the density of other additives like soda water or coconut cream.

Post by Liz Broughton

Rockin’ Pop-Up: What even IS North America?

Santa Cruz County is obviously a part of North America. Right?

Well, it’s a little more complicated than that. There’s the continent of North America, but there’s also the North American tectonic plate — where Santa Cruz County does not reside! While our neighbors in Los Gatos on the other side of the Santa Cruz Mountains are located on the North American Plate, Santa Cruz is located on the Pacific Plate.

There are lots of little (and really big!) geologic surprises across the continent. Join the Geology Gents for this North American road trip!

About the Series: Join the Geology Gents, Gavin and Graham, for monthly conversations about rocks live on Facebook. Each month we’ll explore a different geologic topic, from Santa Cruz formations to tips for being a more effective rockhound. Graham Edwards and Gavin Piccione are PhD candidates in geochronology with the Department of Earth and Planetary Sciences at UC Santa Cruz.

Submit your questions ahead of time by emailing events@santacruzmuseum.org and feel free to include pictures of rocks you’d like identified! Note: you do not need to have a Facebook account to be able to watch the program live.

Watch Past Pop-Ups
Read our blog Rock Record

Selena Stein: Visitor Services Representative

If you’ve visited the Museum on the weekend lately, you may have seen a new smiling face greeting you at the front desk — that of Selena Stein, our Visitor Services Representative who joined us as we reopened our doors this past spring. Selena grew up in Santa Cruz County and even volunteered as a teenager here at the Museum, leading tours and sharing her passion for this land we are lucky to call home.

College in the stunning Pacific Northwest took her away from Santa Cruz, but not for long. Since she returned in 2011 she has worked with children and found nonprofits to be a perfect outlet for serving her community. She is thrilled to be back at the Museum and delights in conversations with visitors of all ages.

“It is such an honor to be part of the Santa Cruz Museum of Natural History’s dynamic team. I adore this beautiful space and eagerly welcome guests of all ages,” said Selena.

As part of our Visitor Services team, Selena excels at making our visitors feel welcome and is delighted to connect community members with the natural world. In her own words, “My goal now is to support visitors to feel comfortable and engaged so they want to connect with and better care for the earth,” which makes her the perfect addition to our organization.

When not representing the Museum at the front desk, Selena can be found outdoors playing in nature with her husband, daughter, and puppy. Her happy place is under the great redwoods and dipping her feet in the ample water sources here in Santa Cruz County. 

Join us in welcoming Selena to the Museum!

CZU AND YOU

CZU AND YOU
Resources for Recovery, Preparedness, and Ecological Understanding from the Santa Cruz Museum of Natural History and Santa Cruz Public Libraries

August 2021

See more CZU AND YOU events

Fire and the Bonny Doon Ecological Reserve with Dr. Jodi McGraw

Many of our native plants in the Santa Cruz Mountains are fire adapted, from the familiar coast redwood (Sequoia sempervirens) to the extremely rare Santa Cruz cypress (Hesperocyparis abramsiana) and Santa Cruz wallflower (Erysimum teretifolium). However, decades of fire suppression have greatly reduced the frequency of fires in our region. The Bonny Doon Ecological Reserve is a rare example of a location that has burned multiple times in just over a decade: in 2008 during the Martin Fire and again in 2020 during the CZU Lightning Complex fires.

Join Dr. Jodi McGraw for an exploration of this unique Santa Cruz sandhills habitat, which is home to the Santa Cruz cypress and Santa Cruz wallflower, and what we’ve learned since the 2008 Martin Fire.

Resources

About the Speaker

Dr. Jodi McGraw is an ecologist who works on conservation projects throughout central coastal California. For the past 28 years, she has been studying the Santa Cruz Sandhills—a unique ecosystem found only in central Santa Cruz County, which supports numerous endangered plants and animals. Her research and conservation management work has addressed how fire can be both a tool and a threat to persistence of the endangered plants, including Santa Cruz cypress and Santa Cruz wallflower, and the native biodiversity in the sandhills.


This program is part of the series CZU AND YOU: Resources for Recovery, Preparedness, and Ecological Understanding from the Santa Cruz Museum of Natural History and Santa Cruz Public Libraries | August 2021