Bowling Ball Beach

Among the splendor of coastal California lies a unique stretch of beach. Approximately 100 miles north of San Francisco and 170 miles south of Redwood National Park, bizarre spheres dot the coarse sand below picturesque sea cliffs.

One might wonder if the colossus from Giant’s Causeway in Ireland had dropped into the Golden State for a few dozen frames of ten-pin.

Colloquially known as Bowling Ball Beach, this expanse in Mendocino County is part of Schooner Gulch State Beach.

It garners its moniker from the giant orbs that sit along the water line, especially visible at low tide.

How did these tremendous bowling balls arrive on a California beach?

Unfortunately, the answer isn’t giants, aliens, or anything else fantastical.

The answer is wonderful geology.

The bowling balls are concretions. These masses form during diagenesis, the process of nature working physically and chemically on sediment deposits. Sedimentary rock – one of the three main types of stones – begins as water sources layer residues on a surface. Over time, these sediments become pressed into hard states that we call rocks. Sometimes during diagenesis, gaps in the sediment fill with solutions of water and minerals. If the minerals precipitate from the solution, they can form cements around a nucleus. For example, a fossil, detritus, or individual sand particles in the layers might find themselves engulfed by mineral cement. If this process continues, spheres form around the nucleus as fresh layers of cement congeal. The result is a concretion.

Concretions do not tend to be as large as the ones at Bowling Ball Beach. Fossil hunters will search for smaller versions to crack open, knowing that the sphere might have coalesced around a preserved ancient entity. When they become as large as the ones at Bowling Ball Beach, scientists dub them cannonball concretions. Only a few other spots feature cannonballs the size of California. In New Zealand, the Moerkai Boulders line the east coast of the South Island. Some locations in Greenland, Canada, Alaska, and along the shore of Lake Huron boast larger concretions. Cannonball River in North Dakota includes a few examples that reach nearly 10 feet in diameter. Sites in Utah, Wyoming, and Kansas have specimens that reach 20 feet in diameter!

At Bowling Ball Beach, the concretions began as mudstone sediment, in formations similar to the cliffs one can still visit today. Over millions of years, wind and rain eat away at the mudstone, while the mineral cement of the bowling balls resists erosion. Eventually, all the softer material washes away, leaving just the giant cannonballs.

We encountered cannonball concretions in a different area of North Dakota, during a visit to Theodore Roosevelt National Park. Along the banks of the Little Missouri River, badlands gave way to gargantuan globes as water slowly eroded the soft mud of the formations. In addition to the huge boulders, one can also view how concretions form within the sediment, as banks with erosion in progress started to show the spherical gems they hid within.

Few places on Earth pack the concretion concentration of Bowling Ball Beach. The sandy strip touts a veritable gutter full of ocean orbs, lined up along a beach-sized alley.

It looks gorgeous.

Researching Bowling Ball Beach led to a wonderful spur in the virtual trail. Looking for video of the area, I discovered footage of the beach from the morning of 11 March 2011. Perhaps that date rings a bell. On that fateful Friday, the Great East Japan Earthquake transpired, producing a tsunami that ravaged Japan. This megathrust temblor knocked out the Fukushima Daiichi Nuclear Power Plant, causing a catastrophe of a level unseen since the days of Chernobyl.

As we learned about tsunamis in the Pacific, an earthquake on one side of the planet can cause havoc on the other. In the case of Bowling Ball Beach in 2011, the effects of the tsunami that raced across the Pacific were thankfully rather slight. The low severity allowed the tsunami to be filmed without much potential danger. In the following video, the water levels might seem unimpressive, especially for a tsunami. However, the timeframe of the changes is rather impressive. Normally, tides go from high to low and vice versa in approximately six hours. The tsunami produced the effects of both tides in about 10 minutes!

If you ever have the opportunity, go to the lanes of California to view this incredible location. Probably try to avoid going during a tsunami, though.