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Rock Record: Santa Cruz Natural History in the Palm of your Hand

By Gavin Piccione and Graham Edwards

Even the smallest and most seemingly ordinary rock tells a story about the processes that have shaped the area in which it is found. From this point of view, beaches are a massive archive of the geologic history of a landscape that contains tiny samples of all the rocks that make up the surrounding area.

In this installment of Rock Record, the Geology Gents (Graham and Gavin) spend a day at the beach exploring the natural history of Santa Cruz looking only at the sand and rocks that fit in the palm of their hand.

Join the “conversation” below, as the Geology Gents chat about what they see when they look at the sand.

Building Beaches through Erosion and Transport

Graham: For all of the attention that beaches get as beautiful places to go lay in the Sun, they really are interesting geologically.

Gavin: We usually think of beaches as a geomorphic landscape: a product of the movement of wind and water and how it shapes and transports geologic material. We don’t usually talk about them as geologic.

Graham: We talk about sea cliff erosion and longshore currents that move sands from these cliffs, as well as nearby rivers and streams. The longshore currents carry their sediment load along the coastlines, and pile them up in certain “low-energy” places, that we call beaches.

Gavin: Ah, yes, I remember we spent some time chatting about this in one of our Rockin’ Pop-ups about Coastal Geology.

A Far-Reaching Collection of Rocks

Graham: But for all our talk of beaches as products of weathering (the breakdown of geologic material) and erosion (the transport of geologic material from one place to another), are they not, my friend, still rocks and something of lithologic interest?

Gavin: Lithology: the study of the characteristics of different rocks and rock types. Well, this sand is made up of rocks, and if we can identify the rock types and note their other properties, then we might be able to determine some interesting things about the geologic origins, or provenance, of these sands, as we often do with larger rocks.

Graham: Let’s take a handful then and look more closely at these sand grains.

Gavin: The sand grains are mostly round. Many are clear and glassy looking, some with a smoky dark grey color. We are familiar with this mineral of course. Quartz!

Graham: Some are blocky looking and cream-white to pinkish in color. Another favorite! Feldspar!

Gavin: Those light-colored feldspars and quartz make up most of the sand, but there are a few other darker minerals. Dark flaky sheets of biotite, black grains of other mafic minerals like amphibole or pyroxene, and some greenish looking minerals – these could be pieces of serpentinite (a Central Coast favorite!) or glauconite (fossilized ocean muck).

Graham: You know, the relative abundances of these minerals really tell you something about how certain rock and mineral types survive the weathering and erosion process. The feldspar and the quartz, especially, are relatively rugged minerals that resist being broken down by the chemical actions of water and the mechanical actions of tumbling around in rivers and waves. But the greenish and darker minerals, which are less resilient to weathering, are very rare. Most of them have been crushed or dissolved to far smaller sizes and have been swept out to sea.

Gavin: So a lot of this is geomorphology? This crushing and grinding of sediments down as they tumble through rivers and waves crash over them along the coast?

Graham: Without question, the erosive forces that shape beaches matter a great deal. If many of these rocks come from the Santa Cruz mountains, they have travelled a great distance and been worn down along the way. Their small size and rounded, almost smooth shapes speak to this long journey.

Gavin: And these pebbles? They are much larger and have sharper angles. There are pieces of mudstone, limestone, and fine and coarse sandstones. Common rocks found along the coast here. Likely these came from sea cliffs nearby that were worn by waves. Since these have not had to travel so far, they have not been weathered quite as much.

Graham: Yes, only the closest rocks can survive in pebble form.

A Hint at the Tectonic History of California

Gavin: And yet, there is one pebble type here that is not familiar from our coastal outcrops: these granite pebbles. Where could these come from?

Graham: Well, granite, made up mostly of quartz and feldspar with large interlocking mineral crystals, is particularly durable when it comes to weathering. Perhaps it has survived a longer journey than the other pebbles.

Gavin: But from where? These granites remind me of the granite of the Sierra Nevada.

Graham: That must be granite from the Salinian Block! Carried up from the region of today’s southern California by the San Andreas fault. These granites formed along with the rocks of today’s Sierra Nevada over 100 million years ago in huge magma chambers. Over the last 30 million years, the San Andreas fault has carried the Salinian block up to the northwest, pulling rocks from the southern extents of the Sierra Nevada along with it.

Gavin: Ahh, and so the Santa Cruz mountains are full of this granite! So that’s where all this quartz and feldspar are coming from?

Graham: That’s right! The “basement” rocks of the Santa Cruz mountains are these Salinian Block granites overlain by sedimentary rocks and metamorphic rocks of the last 30 million years or so. Quartz and feldspar sands come mostly from the granites, though some may be recycled from sandstones.

Gavin: How efficient, that sands from ancient beaches are weathered out of sandstones and returned to beaches today.

Graham: And bits of serpentinite and mafic minerals are also weathered out of other rock types and incorporated into the sands.

Gavin: So the sands at these beaches are not just the result of wind, rivers, and waves. They’re the whole of the Santa Cruz mountains and even nearby coastal cliffs, ground to fine grains and mixed well.

Graham: When we take a trip to the beach and sit in the sand, we really do find ourselves in the rocks of the Santa Cruz mountains. And while it’s a little bit harder to see and recognize each individual rock, when you look closely you can see each little bit of it.

Rock Record is a monthly blog featuring musings on the mineral world from Gavin Piccione and Graham Edwards.

Graham Edwards and Gavin Piccione are PhD candidates in geochronology with the Department of Earth and Planetary Sciences at UC Santa Cruz. They also host our monthly Rockin’ Pop-Ups as “The Geology Gents”.

On the Rocks: Pumpkin Pie Tai

This recipe is part of our series On the Rocks: Exploring Science and Nature through Curated Cocktails.

Autumn is a season of transitions. Darkness noticeably overtakes light more rapidly everyday and months of drought along the Central Coast of California are dampened by the first rains of the season.

There is also a last minute abundance of activity in preparation for shorter, wetter days. Manzanita berries, tan oak acorns, and pine seeds are accompanied by a flurry of wildlife in active pursuit of additions to caches and fat reserves. Buffleheads and goldeneyes return to the river, while the terns and shearwaters leave the Bay. The bigleaf maple becomes a cloud of gold and the conifers remain ever green.

While spring reminds us of rejuvenation, fall recalls the dormancy of nature. Yet in the darkness, the promises of spring ruminate. Seeds that dropped days and months ago rest, wait, and are protected by the soil. As the sun retreats and the fruits fall and the collectors gather their winter rations, each minute of daylight is more precious than the last.

In a spirit of gratitude we offer the following recipe in celebration of abundance, even as the world around us grows darker. So gather up your fall gourds, your squash, your pumpkins. Stew the flesh, plant the seeds, and save a little for this tasty treat.

Ingredients

Pumpkin Seed Simple Syrup:

½ cup of pumpkin seeds
1 cup of water
1 cup of sugar

Pumpkin Pie Tai:

¾ oz pumpkin seed simple syrup
2 oz dark rum
¼ oz allspice dram (or just add some ground allspice)
¾ oz lime
3 tbsp pumpkin puree
1 cup ice

Instructions

To make the Pumpkin Seed Simple Syrup:

Gather seeds from your chosen squash, gourd, or pumpkin (at least ½ cup)
Rinse and dry the seeds
Remove seeds from shells by trimming the edges of the shells with scissors and popping out the seed from within (optional, and interesting!)
Grind ½ cup of seeds in a blender until a powdery consistency
Add 1 cup of water and 1 cup of sugar to blender and mix until smooth
Strain through a coffee filter into a jar. Note: This can take awhile! Just let it sit and do it’s thing. You can also use cheesecloth.
Good for a few weeks in the refrigerator

To make the Pumpkin Pie Tai:

Combine all ingredients
Blend until smooth
Serve over ice
Garnish with your favorite fall spice

Post by Marisa Gomez

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

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

Join us on November 29^th 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

Naturalist Night: Coastal Prairies

California’s Coastal Prairies are a rare and incredibly biodiverse habitat found in Santa Cruz, and the most species-rich grassland type in North America. Despite its rarity and species-richness, this is a habitat-type at risk of continued range loss due to development, fire suppression, invasive plants, and other factors. During this interactive class we will explore these threats to this habitat type, as well as what makes coastal prairies unique, including the geology of coastal terraces, notable species, and ecological factors that have impacted the habitat type over millennia, including cultural burning by indigenous communities.

We are also excited to have a special guest join us this time! Justin Luong is a Ph.D. researcher in Environmental Studies at UC Santa Cruz, currently focused on grassland restoration in California, and will share his research regarding potential impacts on coastal prairies due to climate change and drought.

About the series: Join fellow nature enthusiasts for monthly explorations of the biodiversity of Santa Cruz County. Each month, our Public Programs Manager Marisa Gomez will share the stories of a specific Santa Cruz habitat as we develop our skills as naturalists.

This series will feature a presentation as well as an interactive session and is in partnership with Santa Cruz Public Libraries. Come prepared to share and to learn alongside naturalists deep in their journey and just starting out.

Watch other Naturalist Nights

Collections Close-Up: The Interwoven History of Baskets and Museums

Spend an evening unraveling the complex ways in which consumer trends and museums influenced early 20th basketry collections and craft. Collections Manager Kathleen Aston will elaborate on these trends and how they relate to our collection. Joining us will be Julie Sidel, Interpreter 1 for Santa Cruz Mission State Historic Park, to share how the intersection of museum artifacts and interpretation illuminates daily life at the Santa Cruz Mission.

About the series: Zoom into the stories, secrets, and science of our collections during monthly webinars with Collections Manager Kathleen Aston. This live event is an extension of our monthly Collections Close-Up blog, with added insights and intrigue. Members are invited to participate in this program before it is made available to the general public as well as ask questions directly of Kathleen.

Not yet a Member? Join today!

Rockin’ Pop-Up: Supercontinents

An illustration that shows the continents in different positions on a circle representing the earth. To the right is text and images of two men.

There have been a dozen major and minor supercontinents over the earth’s 4.567 billion year history, and odds are that there will be more. Explore plate tectonics and continental drift in this month’s Rockin’ Pop-Up.

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! Pro-tip: the better the picture, the better the ID.

Watch Past Pop-Ups
Read our blog Rock Record

Collections Close-Up: Making Sense of Made-for-Sale

Walking down the collection’s basketry aisle, drinking in the breathtaking variety of shape, texture, and technique, a glint might catch your eye. Amongst the warm sheen of stripped willow shoot or the bright yellow of dyed porcupine quill, you might catch the unmistakable sparkle of glass. It might surprise you to find such a material on the basketry shelves. Last month we talked about how the spooky or the scary can spark learning opportunities, here at SCMNH we also seek to unpack surprises. Following that course, this month we will be digging deeper into one of the wonders of our basketry collections: a “made for sale” basket.

Following this sparkling glass to its source, you would find a bottle-shaped basket, twined in warm browns and light yellows. The red-brown was likely from tule root, the yellow from tule or cattail leaves, and the black accent, dyed tule. The alternating stripes of color end in an attached coaster-like platform. Taking a closer look, you would discover that the shape arises from the glass bottle it overlays. The basket was collected in Northern California and is attributed to the Klamath River tribes. Today’s federally recognized Klamath River tribes are composed of the Klamaths, Modoc and Yahooskin, distinct peoples whose basketry traditions have similarities.

The absence of specific information about the basket’s weaver is contrasted by our knowledge of the collector. Maude Silvey was already a longtime resident of Santa Cruz by 1970, when she donated her personal collection of more than one hundred baskets to the great joy of museum staff and community. News articles of the time reflect the extent of her interest in baskets, where we learn that “Mrs. Silvey had visited northern California Indian tribes to observe weaving techniques and to obtain baskets for the collection.”

Glass bottle wrapped in basketry, made by the Klamath River Tribes

Her story unfolds against the broader backdrop of collecting trends at the time. Born in the 1880s, Maude Silvey’s early years coincided with the raging temperature of America’s “canastromania” or basket fever. Coined in 1904 by Smithsonian curator Otis Mason, this frenzied collection of baskets swept American culture from about 1890 to 1920. It was spurred by several factors; from the leisure time of an emerging middle class that was being lured west by railroads to the notion that baskets were primitive but pristine objects made by a doomed race that needed to be salvaged. (For an incredible discussion of these interwoven complexities, check out Basket Weavers for the California Curio Trade, a book exploring the lives of Elizabeth and Louise Hickox, weavers from the Klamath River area).

Many well-known collections of California basketry were developed around this time, including that of the Hearst Museum of Anthropology. It was their Lawrence Dawson who helped identify and describe baskets in our own collection in the late seventies. A significant percentage of which were described as “made for sale”.

It seems like a straightforward term at first, applied to baskets made for commercial consumption, like the ones collected on Mrs. Silvey’s trip. Probing the meaning of this category, we might ask how such trips were planned, how the weavers were compensated, and how they emphasized traditional techniques or innovated with them. Early 20th century museums tended to deliberately obscure these kinds of commercial exchanges in their interpretations or avoid displaying baskets that diverged from anthropological understandings of tradition, treating indigenous weavers as if they were confined to the past rather than living craftspersons.

In examining these aspects of our collection, we find that our “made for sale” baskets fit two main types. Some baskets take traditional (a complex term itself, which we might also phrase as “in the style of objects made pre-contact”) forms and functions, and appear to have been sold to collectors unused. An example of these is a cooking basket with neither food residue nor burns from cooking stones.

The other type, which includes the bottle baskets, have forms or functions that are innovations from tradition. Traditional water carrying baskets in California Indian basketry would have relied on watertight weaving and some kind of sealant, rather than a glass center. Other baskets in our collection that follow this type include a tiered hanging shelf, a wall hanging plaque with a holding pouch, and others.

As National Native American Heritage Month, November is an opportunity for institutions to pay deliberate attention to the history and continuing culture of America’s indigenous peoples. Unpacking the words we use to describe the objects in our collections, especially across cultural differences and within the context of colonialism, is a critical component of good stewardship. To delve further into our basketry collections and the forces that shape them, check out this month’s Collections Close Up event on November 12th.

Rock Record: Caverns of Time

By Gavin Piccione and Graham Edwards

Caves are an intersection between natural destruction and creation, where existing rocks are eroded away, and new rocks are continuously formed. Descend into one of the many caves in Santa Cruz and you’ll get a unique viewpoint of the striped marble walls that were built offshore of the area’s ancient shorelines and thrust up onto the continent over the past million years.

This geologic flux also means that one can never enter the same cave twice, since the competing geologic processes of erosion and precipitation are constantly shaping the interior. When you visit a cave, you’ll be a first-hand witness to the geologic processes that shape the Earth.

Gavin and Graham explore speleological features in Empire Cave on the UCSC campus.

Image of marble eroded by water. — Evidence of dissolution in marble in Empire Cave.

Solutional Caves and Karst

The caves of Santa Cruz are called solutional caves because they form when groundwater dissolves pathways through rock, just as sugar or salt dissolve in warm water. However, to dissolve rock, it takes more than just plain old water. Rainwater and groundwater carry dissolved carbonic acid and organic acids that are pulled out of the soil as water percolates down from the surface. In Santa Cruz the bedrock (the solid rock beneath the soil) is mostly marble and made of the mineral calcite which is very susceptible to being dissolved by weak acids like these. Thus, the slightly acidic water can easily dissolve its way into the rock.

You can try this at home or in the field! Find a piece of marble or limestone, scratch at the surface a little bit with a paperclip, key, or coin to make a powder. Drip some vinegar (which is also a weak acid) on the powder and watch it fizz as the calcite dissolves!

As rainwater and groundwater slowly dissolve their way through the marble bedrock over thousands to millions of years little cracks turn into large caves, where the many dissolved minerals such as calcite precipitate, or become solid and separate out of the liquid, forming speleothems. These water-sculpted caves have a distinctive structure and shape: smoothed and rounded marble walls filled with holes and tunnels, covered with speleothems giving most surfaces a ropey, grooved, and nodular texture. In karst systems caves can develop as we’ve described, but if they grow close enough to the surface, the caves can’t support the weight of overlying rock and they collapse forming sinkholes, a familiar feature in the Santa Cruz area.

Since karst caves are formed by flowing water, water often continues to flow into them. Especially in the rainy wintertime, caves can partially or completely fill with water, so it’s important to be very careful whenever entering or exploring caves and postpone your spelunking if it’s rainy!

Sinks of Gandy, a karst cave in West Virginia.

Below the Surface

One of the most scientifically alluring aspects of caves are the preservation of rocks and artifacts that their sheltered interiors provide. Materials within caves are not subject to erosion or weathering to the extent that those exposed to the atmosphere are. Caves also stay the same temperature year-round because they are not affected by atmospheric temperature fluctuation, and instead have temperatures regulated by the ability of the surrounding rock to hold heat. These mild conditions help artifacts like the Dead Sea scrolls and cave paintings to survive for millennia. Similar to archeological preservation, rocks that would normally erode quickly at the surface of the Earth are remarkably well preserved in caves.

Ancient cave painting from Lascaux Cave, France (Wikipedia)

Caves are treasure troves of samples for geologists, biologists, hydrologists, and countless other kinds of scientists. Among the most exciting (at least for us geochronologists) are records of changing climate found in speleothems. As this calcite builds thicker and thicker speleothems, it captures the chemical signature of the climate at the time of its formation. By studying these speleothems, scientists can reconstruct the timeline of global climate change over the past 650,000 years.

Lava tube and lava stalactite at Craters of the Moon National Monument.

Other Types of Caves

Some caves form at the same moment the rock forms, usually from cooling lava. Some examples of these volcanic caves are lava tubes — an open tunnel left behind when a subterranean conduit of lava drains. Caves can also form in the deep chasms left behind by rifts, where volcanoes split the land apart as they swell. Since lava flows, volcanoes can leave all sorts of other cave-like voids behind from the flow, storage, or drainage of lava.

Sea caves, or littoral caves, form where waves carve out deep caverns into sea cliffs, usually into weaker parts of rock. We even see a few shallow sea caves along the Santa Cruz coastline!

Anchialine caves are caverns that connect inland pools, called anchialine pools, to the ocean where the cave ends underwater. The water levels in these pools often rise and fall with the tides, and these are popular sites for scuba-spelunking!

Caves can even form above ground! Talus caves form in the spaces between large boulders at the base of rocky cliffs, and if water flows into or under a glacier, it can melt out glacial caves!

Critters in Caves

*Meta dollof* spider photo from our exhibit Crystals, Caves, and Kilns (2013).

While we most often associate caves with bats, caves are home to all sorts of organisms, including fungi, arthropods (insects, spiders, scorpions, and the like), salamanders, and fish. These creatures are usually adapted to live in these perennially dark, often flooded environments. Because caves are often isolated and disconnected habitats, many creatures that live in caves are endemic, meaning they are found in that cave network and nowhere else on Earth!

For example, the Cave Gulch cave network, just North of Santa Cruz, is home to two endemic species: the spider Meta dolloff and the pseudoscorpion Fissilicreagris imperialis.

Be very conscientious when you visit caves since these are the only homes for many of the creatures that live there. Never leave trash, burn fires, or damage the interiors of caves. If you do go into caves, be sure to pack trash out, or even better, enjoy the cave from the outside and leave its subterranean residents in peace.

Rock Record is a monthly blog featuring musings on the mineral world from Gavin Piccione and Graham Edwards.

On the Rocks: Foraged Liqueur

This recipe is part of our series On the Rocks: Exploring Science and Nature through Curated Cocktails.

During summer months and into early fall, California’s native berry-producing plants provide humans and wildlife alike with a delicious source of nutrients.

[Gathering fruit] required an intimate familiarity with nature and natural patterns. … Indians watched the other animals and linked their behaviors with the ripening of the fruit. Goldfinches, for example, would begin to whistle more frequently when it was time for the Foothills Yokuts to gather blackberries. Keeping a close watch on weather patterns was also important. For example, rosehips…tasted sweetest after the first light frost or cold nights of fall. The Karuk harvested California huckleberries after the first frost because that was when they were sweetest.
Tending the Wild: Native American Knowledge and the Management of California’s Natural Resources by Kat Anderson, 2005

While there are many edible uses for our native berry varieties, a few species are particularly useful for making liqueurs to add a little local flavor to your cocktail game. Our favorites are California blackberry (Rubus ursinus), pink flowering currant (Ribes sanguineum), and blue elderberry (Sambucus nigra ssp. cerulea). Explore our foraging guide before you go out on the hunt and then try your hand at making your own liqueur with our recipe (below).

Foraging Ethics

Before you forage from natural landscapes, it’s important to Know Before You Go. Research the rules and regulations for the landscapes you hope to explore, study the species you may find, and be prepared to identify them accurately. Once you identify the species you would like to forage and you are confident that you are legally allowed to, consider how to do so in a way that does not cause harm. Only take what you will use and leave enough for wildlife.

Biologist of Potawatomi heritage Robin Wall Kimmerer provides an excellent blueprint for ethical foraging based on the indigenous principles of the Honorable Harvest:

Know the ways of the ones who take care of you, so that you may take care of them.
Introduce yourself. Be accountable as the one who comes asking for life. Ask permission before taking. Abide by the answer.
Never take the first. Never take the last. Take only what you need.
Use it respectfully. Never waste what you have taken. Share.
Give thanks for what you have been given.
Give a gift, in reciprocity for what you have taken.
Sustain the ones who sustain you and the earth will last forever.
Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teachings by Robin Wall Kimmerer, 2013

Species and Seasons

Here’s when you are likely to find ripe fruit for the three native species you can use in our liqueur recipe:

Blue elderberry (Sambucus nigra ssp. cerulea): July and August
Pink flowering currant (Ribes sanguineum): July and August
California blackberry (Rubus ursinus): April through September

**Blue elderberry (*Sambucus nigra ssp. cerulea*)**
(Photo from Seven Oaks Native Nursery)

Liqueur Recipe

Ingredients

1/3 cup water
1 cup vodka
1 cup white sugar
1 cup ripe berries

Instructions

Shake together the water, vodka, and sugar to dissolve sugar.
Gently mix together with the berries.
Leave to infuse about 10-12 days until the berries have lost most of their color.
Pour through a fine strainer and discard the berries.
Pour into bottle of your choice to use for months to come!