Gannett News Service
The sandstone formations on the shoreline at the south end of Bellingham have long been sources of wonder for beachgoers and boaters.

This state park rocks

Unusual sandstone formations grace the Bellingham shoreline

GANNETT NEWS SERVICE

Look one minute and you might see a wave, bubbles or sponge. Look back, and you might see something else.

The swirling sandstone formations on the shoreline of Bellingham, north of Seattle on the state's extreme northwest coast, long have been a source of wonder for boaters and beachgoers.

Kayaker and nature photographer Gene Davis, a retired border patrol officer, has clicked through many rolls of film, exploring the interplay of light on the curved surfaces of the sandstone.

"It's always changing," he says.

George Mustoe of Western Washington University's geology department has researched the natural sculpting phenomenon, which geologists call "honeycomb weathering."

It's a phenomenon that can be observed throughout the world on shorelines, in deserts and in the Antarctic. It might even be extraterrestrial -- photos from the Viking space mission in 1977 show rocks with patterns that resemble the pocks and puckers found on the sandstone at Larrabee State Park, which contains the northwest Washington spectacle.

Similar shoreline patterns raised the curiosity of Charles Darwin in 1836 when he visited King George's Sound in Australia. Darwin was puzzled by areas where cavities within shoreline rocks were separated only by thin mineral walls. He hypothesized that the thin walls were the legacy of trees that grew before the rock formed.

While the sandstone formed around the tree branches and roots, the plant matter rotted away, replaced by rock that ended up being harder that the sandstone, Darwin wrote.

"He got it badly wrong," Mustoe says.

In fact, honeycomb weathering results from the effects of salt and water. In storms and high tides, the rocks above the shoreline get splashed with salt water. When the water evaporates, salt crystals form inside crevices and the force of the expanding crystal can break the rock, creating a small hole that becomes larger as the process repeats itself over time.

This does not answer Darwin's question of how the thin walls persist. Mustoe's answer is that algae and lichens growing on the side of the cavities seal the rock, making it less vulnerable to the corrosion still wearing out the back. A close look at some of these walls will show dark growth of the sides, Mustoe says.

Honeycomb weathering presents no erosion threats that would undermine the foundations of nearby homes, but it doesn't take long to make its mark.

"The stuff actually grows fast," Mustoe says.

Honeycomb patterns can appear as soon as 25 years after a rock is placed in a vulnerable spot. After centuries, a strip about three feet above the shoreline can recede as if a giant had bitten into the rock face. Eventually, wave action smooths the forms that curve as much as if they had been designed by master sculptor Henry Moore.

Some spots have mushroom-shaped formations, with an outcrop of rock being larger on top than on the bottom. Similar formations show up in deserts, Mustoe says, but there the action isn't from salt water, but from a combination of salts and dew low to the ground.

"The dew cycle in the colder part of the year is just like the tide cycle," Mustoe says.

Larrabee State Park

- Getting there: Seven miles south of Bellingham on Samish Bay, situated off Chuckanut Drive near the Whatcom/Skagit County border.

- Features: Established in 1915 as Washington's first state park, Larrabee is also one of the largest, spanning 2,683 acres, from sea level to 1,940 feet elevation. It occupies most of the western side of Chuckanut Mountain. The park offers a tidal and wooded wilderness for picnicking, boating, fishing, clamming, hiking, camping, water skiing, crabbing, beachcombing and scuba diving.

- For information: Write to Larrabee State Park, 245 Chuckanut Drive, Bellingham WA 98226, or call (360) 676-2093. Web site: www.ohwy.com/wa/l/larrawsp.htm.

- Bellingham information: Contact the Bellingham/Whatcom County Convention & Visitors Bureau at (360) 671-3990. E-mail: tourism@bellingham.org. Web site: www.bellingham.org.

The Olympian Copyright 2001

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