geology – Swell Lines

Brush Strokes: Blaze Syka

About Blaze Syka:
I grew up in San Diego, CA and demonstrated an interest in the ocean and art at an early age. I swam, played waterpolo, lifeguarded, and drew waves throughout high school and moved up north into colder waters for college and his professional career. My work with exploring and diagramming surf breaks with cross sections is fairly recent but I enjoy exploring angles and challenges in new pieces rendered in this style. Each new work is almost like a puzzle and I’m always looking to add new elements to keep them fresh. I’m currently investing more time into my artwork while working on post graduate studies. I always keep my wetsuit and a pair of bodysurfing fins in my car.
www.BlazeSyka.com
@blazesykd

May, 2016April, 2017

Swell Lines Magazine

The Science of Coastal Geology- Part 1

We’re all beach people. We’re attracted to the coast for the beauty, serenity and the waves. There are many variations to coastlines around the globe and these changes are the factors that create the great variety of waves. In this multiple-part article, we’ll analyze coastal geology to better understand how differences in a coast’s dynamics dictate how waves break in a given area.

Geology is the Science of the rocks that create landforms and the processes that change those rocks.The coastal environment has many dynamic factors. Plate tectonics, wave energy, weather, rivers, and humans all have an impact on coastal geology. The coast is always changing. Some changes happen daily, like the movement of sand. While others, like the uplifting of land from plate movement, take place over the course of hundreds, thousands and millions of years.

If you observe any stretch of coast, you’ll see that waves break differently on varying parts of the beach. This is because the Ocean bottom varies. Bathymetry is the underwater contours of the seafloor. It is often overlooked as a surf variable. We cannot directly see it and much of it is fixed for our lifetime. But a closer investigation reveals the dynamic and vital story of our coastlines.

Swell approaching a coastline will always refract and bend toward shallow water. Reefs, sandbars, points and submarine canyons cause swell energy to focus and shoal. Because there is a variety of depths along a coast, waves break differently everywhere. Sandbars frequently shift and move as the sand is carried by longshore currents. California reefs are uplifted remnants of the coastal bluffs and marine terraces. Points are created by the uneven shape of a dynamic coast. Submarine canyons form when fresh water runs off the land and erodes a chasm in the continental shelf.

California’s coast primarily consists of sedimentary rocks in identifiable layers. All of these layers are associated with ancestral rock formations and their subsequent weathering, erosion and deposition. According to a sign at San Elijo State Beach, “The coastal bluffs were formed by the accumulation of mineral and organic sediments. In more recent times, the Ocean level has receded, leaving the sedimentary deposits exposed in elevated marine terraces. Once exposed, these terraces were eroded along the seaward margins, leaving the steep coastal bluffs present in the park today.”

Three prominent layers include:

The Del Mar Formation– the bottom and oldest layer of the San Diego coast sedimentary rocks. It is often greenish or gray mudstone, containing many fossils, laid down in muddy lagoons 45-50 million years ago. The Del Mar Formation now forms many of the reef wave setups we have in San Diego.

Torrey Sandstone– a large layer of light colored sandstone that is the main constituent in San Diego’s coastal bluffs. It is roughly the same age as the Del Mar Formation and was laid down as a sandbar and beach deposit.

Monterey Formation– an oil rich layer that is responsible for the tar on beaches and the offshore oil rigs towards Santa Barbara. It is 6-16 million years old and comprises the remains of billions of microorganisms that once swam in a shallow sea. When they died, they sank to the bottom and were covered by sand and silt. With pressure, heat and time, the organisms became hydrocarbons: the source of our much beloved oil. The Monterey Formation is seen throughout the Central Coast and into the Coastal Range Mountains. It makes up many of Central California’s reef breaks.

-KS

Sources:
Mark Bordelon- Irvine Valley College
PBS Coastal Geological Processes

July, 2015February, 2018

Swell Lines Magazine

The Science of Sand

It is everywhere. On the streets, your feet and in your sheets. In your car and your carpet. Sand. One of the most useful resources on Earth and the foundation of our waveriding dreams. Concrete, glass and microprocessors, sandbars and beaches: sand is ever-present in our lives. Where does it come from? Why is it different across the globe? How does it impact the formation of waves?

Indonesia. Black sand from volcanic rock, rounded by flowing water.

In geologic terms, “sand” refers to a certain size of particle in sediment: smaller than gravel and larger than silt. A sand particle measures between 1/16mm and 2mm in diameter. The main mineral components of beach sand include: quartz, feldspar and hornblende. All three are silicate minerals. These minerals, with their different combinations of silicon and oxygen, make up 90% of the Earth’s crust.

Quartz is the most abundant beach sand mineral because it is resistant to chemical weathering and thus able to withstand the tumultuous journey from mountain to beach. Rock forms in a variety of ways inside and out of Earth. Sediments layer to form sedimentary rock. Liquid magma cools inside and lava hardens outside Earth to form igneous rock. Forced upward by plate tectonics, rocks are exposed to wind and rain, freeze and thaw, plant roots and battering waves. Weathering slowly works boulders to cobbles to gravel to sand to silt and then to clay.

Encinitas, CA. Fine grains of quartz and other silicate minerals.

Erosion moves the sediments and deposition drops them off in a new location. In California, boulders cleave off granite mountains to the east. Rivers carry chunks of the mountain downstream, continuing to break it down along the way. Rivermouths flow into the Ocean, depositing cobbles and sand on the beach. California beach sand is a mixture of these inland minerals and the erosion of the marine terrace (sea cliff). Wave action along the cliff bottom weathers large masses of the sedimentary rocks. The rocks fall to the beach and are gradually worked into sand. California beach sand also contains a living ecosystem and various other detritus.

North Shore of Oahu. Shell, volcanic rock and coral.

Because there are many different rocks and minerals, there is a great variety of sand across the world’s beaches. Differing landforms and ecosystems create different sand. Hawaiian beach sand is a mixture of eroded volcanic rock, shell fragments and parrotfish waste. They eat coral that passes through their digestive tract and is then deposited as sand. Sand partially composed of the remains of living organisms is called biogenic sand. Many of the world’s tropical beaches contain fragments of coral and shell.

Tweed River used to provide sand to Snapper and Kirra. Image: Google Maps

All Ocean waves break over some amount of sand. Point breaks often have rivermouths nearby to nourish the sandbars that wrap around their shores. Reef breaks become covered by sand during a long flat spell. The next swell removes sand from the reef to expose the proper wave-making bathymetry. Beaches change shape frequently as sand is moved by swells, storms and longshore currents.

Wind bedforms. Oceano Dunes, Pismo Beach.

Beachbreaks are synonymous with shifting sand. The formation of sandbars is a complex process. A bedform is created when a fluid flows over a moveable surface; in this case water waves over the sandy seafloor. It is the same process as wind blowing over a sand dune. Ripples form in the surface, sand falls out of suspension in the water and continues to build up the sandbar. Incoming swell shoals on the sandbar and a breaker forms. The water flowing back out to sea becomes a rip current that reshapes the sandbar. When conditions align, perfectly shaped waves can result.

The shape of the beach and the type of the waves that break there are often dependent on the size of the sand grains. Wide flat beaches are formed from smaller grained sand than steeper beaches. North Carolina coastal geologist, Gregory Rudolph, puts it this way, “If you fill a bucket full of mud and pour; it will essentially ooze out and your pile of mud will look like a pancake. Fill that same bucket with gravel and you’ll have a pile that is almost as high as the bucket itself.” Much to bodysurfer’s delight, steep beaches often create hollow, womping shorebreak waves. Swell energy comes out of deeper water to load up and plunge powerfully on the coarse sand. There is something special about washing up and back down a steep beach fully covered in soft sand.

Granitic gravel variety in Yosemite Valley. All will become sand.

Vital to beach communities and even controversial in some, sand is pervasive in our lives. Embrace the sand in your ears. Cherish an afternoon spent basking on the beach. Appreciate the geology that forms our coastlines and shapes our waves. Eventually, every grain of sand on our beaches will return to the internal furnace of the Earth to become magma and then mountains again. What waves will break on that next generation of sandbars?

-KS

Sources:
SandAtlas.org
National Geographic- Parrotfish
Carteret County, NC- Shore Protection Office

August, 2014February, 2018

Swell Lines Magazine

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