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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

USGS Geologic map of Santa Cruz County, California

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.

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).

Explore Online Rock Resources

Shop the geology and paleontology section of our online store

Books and Papers

9/24-9/25 Sea Otter Week Pop-Up

Swing by Lighthouse Point along West Cliff Dr. in Santa Cruz to spot sea otters with the Santa Cruz Museum of Natural History! Get a closer look at our furry friends from afar through spotting scopes and up close with specimens from the Museum’s collections. These pop-ups are in celebration of Sea Otter Awareness Week.

Friday, September 24 & Saturday, September 25
Lighthouse Point | 10 a.m. to 2 p.m.

Notes about the event
No registration required. Swing by anytime from 10 a.m. to 2 p.m.! The program is appropriate for learners of all ages. Please follow current state and local guidelines for COVID-19.

A Cyclist’s Guide to the Wildflowers of Santa Cruz

A Cyclist’s Guide to the Wildflowers of Santa Cruz

Pedaling to petals, it’s almost too good to be true.

Add a little color to your bike ride with this mobile wildflower guide from the Santa Cruz Museum of Natural History. This flower field guide and bike route map will help you on your treasure hunt. Wildflowers can be fleeting so keep these routes on rotation to avoid missing the show!

Wildflower season varies from year-to-year, usually starting in March, picking up in April, and winding down in May. Some of these flowers pop-up early in the season, while others are late bloomers.

Easy | Moderate | Strenuous | Mountain Biking

Download the PDF version to take on the road
Learn more about Bike Month Santa Cruz

COASTAL CRUISING | Easy

This easy route takes you through some of the best wildflower viewing in the heart of town. You might think wildflowers belong in the wild, but with habitat loss such a huge threat to plant diversity, creating space for native plants in our urban areas is more important than ever.

Getting There

All Trails Route | Distance 7.05 mi | Elevation Gain 203 ft
This route cuts through town and along the coast, starting at Arana Gulch, then heading to the Santa Cruz Museum of Natural History, and ending at the UC Santa Cruz Coastal Science Campus. Then double back and see if you missed anything!

  • Santa Cruz Tarplant
    Holocarpha macradenia
  • California Poppy Maritime Variety
    Eschscholzia californica var. maritima
  • California Buttercup
    Ranunculus californicus
  • Common Self Heal
    Prunella vulgarus
  • Gumplant
    Grindelia stricta var. angustifolia
  • Western Blue Eyed Grass
    Sisyrinchium bellum

Santa Cruz Tarplant (Holocarpha macradenia)
Location: Arana Gulch

This rare and endangered plant endemic to Northern California is the reason we have Arana Gulch Open Space. The City manages the park in a way that promotes the success of this species. Adapted for disturbance historically common in coastal prairies, cows graze the landscape much like megafauna used to thousands of years ago.

Photo from Friends of Arana Gulch.

California Poppy Maritime Variety (Eschscholzia californica var. maritima)
Location: Santa Cruz Museum of Natural History

The Garden Learning Center at the Museum features several habitats. The front garden is a coastal prairie featuring our local variety of California poppy in abundance! Our maritime variety has a darker center with light edges, whereas the standard poppy is more orange throughout.

California Buttercup (Ranunculus californicus)
Location: Santa Cruz Museum of Natural History

These bright, shiny yellow flowers often bloom earlier than many other species, and will go to seed and return to a dormant state by early summer. Buttercups can be a nice source of nutrition and can be toasted or ground up and added to baked goods.

Common Self Heal (Prunella vulgarus)
Location: Santa Cruz Museum of Natural History

In addition to attracting pollinators, this edible plant has long been used as a remedy for a variety of ailments, including sore throats and muscle aches. Some of its other common names include heal-all, woundwort, heart-of-the-earth, carpenter’s herb, and brownwort.

Gumplant (Grindelia stricta)
Location: UC Santa Cruz Coastal Science Campus

In the early stages of blooming, the head of this yellow aster produces copious white exudate (i.e. goo). Indigenous cultures have traditionally used this exudate as an adhesive.

Western Blue Eyed Grass (Sisyrinchium bellum)
Location: UC Santa Cruz Coastal Science Campus

Actually a member of the iris plant family, blue-eyed grass produces deep purple flowers in late winter and early spring. The genus name means “pig snout”, referencing the sweet roots that were dug up by pigs in their native grasslands.

Explore our Guide to the Garden Learning Center

MEADOW MILES | Moderate

Sometimes you have to work a little for flowers, especially the really good ones. This route has you summiting one of our biggest in-town hills by biking up Bay St. towards campus. Part of the UC Santa Cruz Campus Natural Reserves, Mima Meadow is a coastal prairie featuring geologically interesting mima mounds and some of our most sought after flowers. Walk your bike through the paths to help protect the endangered Ohlone Tiger Beetle (Cicindela ohlone).

Getting There

All Trails Route | Distance 5.71 mi | Elevation Gain 427′
This route has you starting at the coast side of Bay St., taking it all the way to the top, then turning left on High St. and continuing on Empire Grade until you reach the closed gate to Mima Meadow on your left (just past the Arboretum). To get into the Meadow, you will need to use the steps in the fence at the fire road. Either lock your bike up at the Arboretum across the street, along the fence, or walk with it along the trails.

From here you can look down on your starting location along the Monterey Bay as you walk the trails. Stop by the UC Santa Cruz Arboretum and Neary Lagoon on your way back!

  • Monterey Mariposa Lily
    Calochortus uniflorus
  • Yellow Mariposa Lily
    Calochortus luteus
  • White Brodiaea
    Triteleia hyacinthine
  • Harlequin Lotus
    Hosackia gracilis
  • Sky Lupine
    Lupinus nanus
  • Golden Broadiaea
    Triteleia ixioides ixioides

Monterey Mariposa Lily (Calochortus uniflorus)

The genus Calochortus contains some of our region’s most sought-after flowers. This rare species has grass-like leaves and upright flowers shaped like a bowl, which bees often rest in. Featured here is a longhorn bee (Melissodes sp.)

Yellow Mariposa Lily (Calochortus luteus)

Another member of the Calochortus genus, this California endemic flower is more widespread than C. uniflorus, but can still require a bit of a hunt. Conveniently, this species pops-up right near the gate to Mima Meadow. Turn right on the first trail you see and make sure you don’t discount every bright, big flower as a poppy!

White Brodiaea (Triteleia hyacinthina)

Also known as fool’s onion, this plant has an edible bulb, though it lacks the familiar onion smell.

Harlequin Lotus (Hosackia gracilis)

This rare plant belongs to the pea family and is unlike any plant you’re likely to find with its mix of sherbet colors. It’s thought to be a larval food plant of the Federally Endangered lotis blue butterfly (Lycaeides argyrognomon lotis).

Sky Lupine (Lupinus nanus)

Our region hosts many types of lupines and they can be challenging to tell apart. Even when not in bloom you can identify a lupine by its palmate leaves (five fingered like a hand).

Golden Brodiaea (Triteleia ixioides subsp. ixioides)

This cheerful yellow flower is in the same genus as the white broadiaea and also grows from a bulb.

BONNY DOOM | Strenuous

The Bonny Doon Ecological Reserve is a spectacular location for exploring nature. An example of the rare Santa Cruz sandhills habitat, the soil is comprised of ancient seabed deposits and is very nutrient poor. For that reason, highly specialized plants grow here and nowhere else. It also burned partially in the CZU Lightning Complex fires, as well as during the Martin Fire of 2008.

Getting There

All Trails Route | Distance 24.85 mi | Elevation Gain 2,612 ft
From Mima Meadow, continue on Empire Grade. Turn left onto Smith Grade. You’ll meander through parts of the CZU Lightning Complex Burn Zone before reaching Bonny Doon Rd. Turn right and continue onto Pine Flat Rd. before taking a slight right onto Martin Rd. You’ll know you’re getting close when the habitat changes drastically, the sky opening up above you. Bike locking is a challenge, but you also don’t want to bring your bike along these trails.

When you’re done, double back down Bonny Doon Road to Highway 1 and take that back to the Coastal Science Campus for a relaxing view.

  • Ben Lomond Spineflower
    Chorizanthe pungens var. hartwegiana
  • Bush Poppy
    Dendromecon rigida
  • Ben Lomond Buckwheat
    Eriogonum nudum var. decurrens

Ben Lomond Spineflower (Chorizanthe pungens var. hartwegiana)

You really have to see this flower in person to understand just how tiny it is. This rare member of the buckwheat family is found only in our local Santa Cruz sandhills habitat. You don’t have to travel far along the trail to find dense mats of this flower when in bloom.

Bush Poppy (Dendromecon rigida)

This shrub offers a pop of color to the Reserve when in bloom and can reach many feet high.

Ben Lomond Buckwheat (Eriogonum nudum var. decurrens)

Belonging to the same family as the spineflower, this variety of naked buckwheat is also rare and endemic to the Santa Cruz sandhills. Its leaves form dense basal rosettes and the tiny flowers sit atop long spindly stems.

WILDERIN’ OUT | Mountain Biking

For those who prefer dirt to pavement, there’s great wildflower peeping along the trails of Wilder Ranch State Park. There’s not a bad trail for finding flowers, but this simple route takes you straight up towards the top of the park, passing through some of the best coastal prairie grasslands in the County. On the way back you’ll pass through redwood forest and woodland habitats.

Getting There

All Trails Route | Distance 11.75 mi | Elevation Gain 1,286 ft
This route takes you along the coastal bike path past invasive plants like wild radish, marigold, acacia, and french broom. When you get to the end of the trail, turn right and head up! You’ll take Engelman’s Loop to Long Meadow Trail, then double back and take the Wild Boar Trail for a change of scene and some fun twists and turns.

  • Common Fiddleneck
    Amsinckia menziesii
  • Western Heart’s Ease
    Viola ocellata
  • Fairy Lantern
    Calochortus albus
  • Purple Owl’s Clover
    Castilleja exserta
  • Fremont’s Deathcamas
    Toxicoscordion fremontii

Common Fiddleneck (Amsinckia menziesii)

These early bloomers with their charmingly twisted tops will pop-up in droves. As the plant grows, the stem uncoils, and new flowers emerge, while the old flowers develop into seed pods along the lower part of the stem.

Western Heart’s Ease (Viola ocellata)

Wilder Ranch has a handful of native violets, ranging in colors from white to yellow. These are often found in the transitional zones from meadow to chaparral to redwood forest.

Fairy Lantern (Calochortus albus)

Another stunner from the genus Calochortus, this species has a different stature than C. uniflorus and C. luteus. Rather than a bowl shape, this species has flowers that drop like little lanterns. Find it on the edges of grassland and woodland habitats.

Purple Owl’s Clover (Castilleja exserta)

This species belongs to the genus Castilleja, which includes Indian paintbrushes. Like other related plants in the family, this is a hemiparasite which derives some of its nutrients directly from the roots of other plants.

Fremont’s Deathcamas (Toxicoscordion fremontii)

This perennial plant grows back year after year from bulbs underground. It’s referred to as deathcamas because all parts of the plant contain a toxic alkaloid that some consider more potent than strychnine. 

There are so many more wildflowers to see in Santa Cruz than are included here. If you find something you don’t recognize, consider taking its picture and uploading it to iNaturalist. The app will suggest potential species and your observations will be recorded as biodiversity data, helping us better understand our natural world.

Mural of an Ohlone village by artist Ann Thiermann

These routes traverse the traditional and unceded territories of the Awaswas-speaking Uypi and Cotoni tribes. Today these lands are stewarded by the Amah Mutsun Tribal Band who are working hard to fulfill their obligation to Creator to care for and steward Mother Earth and all living things through relearning efforts and the Amah Mutsun Land Trust.

This guide was created in honor of Bike Month (May 2021) in partnership with Ecology Action. Learn more.

Fire Ecology and the CZU Lightning Complex

Resources for exploring fire ecology in Santa Cruz County and learning about the impacts of the CZU Lightning Complex. Contribute to our understanding by joining the CZU Lightning Complex and Community Science Project.

UPCOMING EVENTS

    PAST RECORDINGS AND ARTICLES

    How to Make a Spore Print

    Sure, you can make beautiful pieces of art from the spores of a mushroom, but you can also learn more about the mushroom in the process, too!

    Watch this video to learn how to make a spore print and explore more resources below.

    Do you know what a spore is?

    A spore is a reproductive cell. Some plants make them but bacteria, algae, and fungi make them too. Spores are to mushrooms as seeds are to plants. Spores are how mushrooms reproduce and make more mushrooms. 

    The first step to making a spore print is collecting a mushroom.

    You can collect from:

    • Your yard
    • Your friend’s yard (with permission)
    • Local city park. 

    You cannot collect from:

    • Someone else’s property without permission
    • State parks

    Please follow the rules of where you collect and make sure it is okay to collect from the area you are visiting. 

    Bring something to carry your mushroom with, like a basket or paper bag. You don’t want them to get squished in your pocket! Only pick the mushroom if there are a lot around because they are important for the environment. 

    Do you know why mushrooms are important? 

    Mushrooms are decomposers which means that they break down dead materials such as fallen leaves and logs to make soil and nutrients that help other living things survive. Remember to wash your hands after handling mushrooms!

    Once back home:

    1. Gather jars or containers big enough to place over the mushrooms. Gather white and black paper. It is okay if you only have white paper, but some mushroom spores are white and therefore they won’t show up on white paper that well. 
    2. Take the stems off the mushrooms using your hands or scissors. 
    3. Place the mushrooms with the gills or pores facing down onto the paper. Then place the container over the mushroom to create an airtight seal.
    4. Leave the mushrooms covered anywhere from a couple hours to overnight based on how fresh the mushrooms are.
    5. After you let the mushrooms sit for a while, carefully pick up the containers and the mushrooms to reveal the spore print. Spore prints are fragile, so try to avoid touching it. 

    Resources for identifying mushrooms

    Laura Hecox Collections

    historic photograph of Laura Hecox standing along the coast

    Laura Hecox was an extraordinary woman and a brilliant amateur scientist who even had species named after her. Laura was the Santa Cruz lighthouse keeper from 1883 to 1916, and a renowned collector whose lighthouse museum was known far and wide. Contemporary descriptions in newspapers, correspondence, and other publications describe a stunning collection that occupied a room’s worth of cabinets on subjects from marine life to gems and minerals to ethnographic collections. Her collection of natural history specimens, artifacts, and curios was gifted to the people of Santa Cruz in 1904 and is the foundational collection of the Santa Cruz Museum of Natural History.

    Over the years, as Laura’s museum found homes in different community locations, portions of the collection were lost to time. Today, we strive to reconcile this loss with the honor of preserving what we still have, and the responsibility of making it available to our community. Laura’s tireless curiosity about the world around her continues to inspire our organization, even as we continue to learn more about her legacy.

    Descriptive Guide to the Laura Hecox Collection (PDF | HTML)

    Laura Hecox Scrapbook

    While Laura meticulously cataloged her collection, she kept no known diary. Contemporary authors reference her scientific correspondence, yet none of these writings is known to have survived. Laura was, however, an avid scrapbooker. We are excited to provide complete access to the largest of Laura’s surviving scrapbooks. The scrapbook featured below is one of the few means by which we can learn more about Laura’s private life and the historical context in which she lived.

    Her interests on the page were just as diverse as when collecting physical materials. In her scrapbook, beginning with an 1895 article on women lighthouse keepers, you will see articles on topics ranging from shell identification to women’s suffrage. We are always eager to learn more about Laura, as well as the natural and cultural history of late 19th century Santa Cruz.

    Laura Hecox ScrapbookDownload

    We are proud to represent Laura’s legacy. However, the content reflected in these clippings is historical in nature. The views and opinions expressed within are not necessarily those of the museum itself. 

    This project is indebted to the ongoing research legacy of Frank Perry, and is made possible by a partnership with the Santa Cruz Public Libraries.

    To learn more about the Laura Hecox collection or set up a research appointment, email collections@santacruzmuseum.org

    Laura Hecox Resources

    A selection of items from the Laura Hecox Collection

    First Peoples of Santa Cruz | Lesson Intro

    Note about terminology

    While we know it is common to use the term Ohlone to describe the Indigenous people of the Santa Cruz area, these lessons use Awaswas (the language once spoken in what is now Santa Cruz County), Uypi (the name of the tribe that lived in what is now the City of Santa Cruz), and Amah Mutsun (the name of the tribal band that represents the Santa Cruz region today).

    If you have been using Ohlone with your class, you can share that Ohlone is the name of the culture that these tribes belong to (culture is the way you live your life). Further explore the tribal distinctions along the Central Coast with this map.

    This video is the introduction to our First Peoples of Santa Cruz digital lessons. Download the lessons by filling out the form on this page.

    11/30-12/11 Member Exclusive: Holiday Shopping by Appointment

    Banner advertising member only holiday shopping

    November 30 – December 11
    Mondays – Thursdays | 9 a.m. – 5 p.m.     | 30 minute appointments*

    Museum Members are invited to schedule exclusive 30 minute appointments to browse and shop in the Museum’s onsite Store. Get ahead in your holiday shopping and find the perfect gift for the naturalists in your life. The Museum store features a wide array of unique books, field guides, gifts, toys, and souvenirs for nature-enthusiasts of all ages. Every purchase in the Museum Store supports our mission, programs, and exhibits.

    To Schedule: Contact liz@santacruzmuseum.org or call 831-420-6115x10

    *Appointments limited to household groups, max of 5 people.

    Looking to make another arrangement or would like gift suggestions? Just ask and we’ll be happy to help! You can also browse a selection of our merchandise in our Online Museum Store.

    Not yet a Member? Join today for as little as $15/year.

    11/29 Museum Store Sunday Sale

    Banner advertising Museum Store Sunday

    Sunday, November 29 | All Day
    Shop Online
    Coupon Code: MSS2020

    Join us on November 29th for Museum Store Sunday, a worldwide event celebrating the unique and educational value that museum stores provide for their communities. Use the coupon code “MSS2020” to get 10% off in our Online Museum when you check out. This deal will only be available on Sunday, so mark your calendars now!

    The store at the Santa Cruz Museum of natural history is your resource for books, field guides, and educational toys that encourage connections with nature. It is also the perfect place to pick up unique souvenirs and gift items from local Bay Area artisans. Discounts will also apply to the online selection of items from the Santa Cruz Surfing Museum.

    SHOP NOW