How did that get here?

EDMONDS — After untold millennia of glacier surfing, this big rock is taking a quick, 12,000-year break.

Geologists believe a boulder located in a mobile-home park just off Edmonds Way is a

n “erratic,” a stone deposited in the area by glaciers during the ice age.

Looking at the rock — roughly 12 feet high by 10 feet wide by 15 feet long — “erratic” would seem to be a misnomer.

It seems very stable.

It’s about the size of a camper, estimates Dave Tucker, a research associate in geology at Western Washington University in Bellingham. Tucker discusses the boulder, and others, on his website, titled Northwest Geology Field Trips.

Many erratics are located around the Puget Sound area, from some as big as a house to beach-ball-sized stones buried in our back yards, said Donn Charnley, a professor emeritus of geology at Shoreline Community College.

The stones were picked up by glaciers and moved, maybe many times, during the ice age that began about 2.5 million years ago, geologists say. In this area, the ice sheets receded for good about 12,000 years ago, Charnley said. The stones were left behind.

In some cases, the large stones remain in neighborhoods or small towns, and houses or streets are built around them, said Dale Middleton of Seattle.

He is vice president of the “Puget Lobe” chapter of the Ice Age Floods Institute, a study group of geology enthusiasts and others in Washington, Oregon, Idaho and Montana. The local chapter takes its name from the Puget lobe, the river of ice that carved out Puget Sound. The group meets in Edmonds and draws people from around the region.

Other examples of large erratics include the Wedgwood Rock in the Ravenna-Bryant neighborhood of northeast Seattle, and Big Rock, in Coupeville on Whidbey Island.

Another large stone on Whidbey, the Waterman erratic, is located in the woods near Langley. This “hulking brute,” as Tucker calls it, is 33 feet tall, he says. The one in Coupeville is about 22 feet high.

Sometimes, developers don’t leave the big rocks intact.

“They’ll just blast those suckers out of there,” Middleton said.

An erratic is any stone that’s been transported from its place of origin, Charnley said. It’s identifiable by having a different composition than the stones and the ground around it.

Geologists believe the Edmonds erratic, like many others in this area, is from the Fraser River valley in southern British Columbia, having similar characteristics to stones in that area.

The stone is a conglomerate, meaning it’s made up of many stones cemented together. Several types of substances, such as quartz, iron oxide, calcite or clay, can serve as the cement, Charnley said.

The weight of the ground above the stone and the moving plates of the surface of the Earth presses, squeezes and heats the minerals so they meld together.

Charnley believes the Edmonds boulder is held together by quartz.

“It’s been really cooked. It’s really hard,” said Charnley, 83, of Shoreline. If someone were to take a hammer to it, “it would probably bounce right off of it.”

Tucker describes the Edmonds erratic as a breccia, a type of conglomerate in which the smaller stones that make it up are angular, rather than rounded off by movement over time. Breccias are often found close to their places of origin, which sometimes are volcanic.

It’s impossible to tell exactly where the rock came from unless a cross section of the stone can be examined, Charnley said. Because of the boulder’s hardness, however, it could take a jackhammer to get a large piece off it, he said.

Still, at some point, someone managed to drill into the top enough to install a metal post of some type, to which is attached a rope.

Neighborhood kids come over and climb on the boulder, though either the rope or its attachment to the post is now broken, according to Zina Stewart, who lives in the mobile home next to the rock. Someone also has set up a small, improvised bench on another part of the top of the rock.

The landscaped area around the boulder is well kept, with the rock’s smooth, undulating surface almost fully exposed.

Considering its history, not much is likely to faze this massive mass of mineral. Its thousands of years in Edmonds have been but a tick on the clock of its life.

Charnley believes the stone is anywhere between 50 million and 300 million years old.

“It’s been around awhile,” he said.

Bill Sheets: 425-339-3439; sheets@heraldnet.com.

More boulders

For more information on ice age boulders in the Puget Sound area, go to Northwest Geology Field Trips at http://nwgeology.wordpress.com. For information on the Ice Age Floods Institute, go to www.iafi.org.

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Local News

Olivia Vanni / The Herald 
The Mukilteo Lighthouse. Built in 1906, it’s one of the most iconic landmarks in Snohomish County.
The Mukilteo Lighthouse. Built in 1906, it’s one of the most iconic landmarks in Snohomish County. (Olivia Vanni / The Herald)
Mukilteo mayor vetoes council-approved sales tax

The tax would have helped pay for transportation infrastructure, but was also set to give Mukilteo the highest sales tax rate in the state.

Marysville Mayor Jon Nehring gives the state of the city address at the Marysville Civic Center on Wednesday, Jan. 31, 2024, in Marysville, Washington. (Ryan Berry / The Herald)
Marysville council approves interim middle housing law

The council passed the regulations to prevent a state model code from taking effect by default. It expects to approve final rules by October.

x
State audit takes issue with Edmonds COVID grant monitoring

The audit report covered 2023 and is the third since 2020 that found similar issues with COVID-19 recovery grant documentation.

Bothell
Bothell man pleads guilty to sexual abuse of Marysville middle schoolers

The man allegedly sexually assaulted three students in exchange for vapes and edibles in 2022. His sentencing is set for Aug. 29.

Larsen talks proposed Medicaid cuts during Compass Health stop in Everett

Compass Health plans to open its new behavioral health center in August. Nearly all of the nonprofit’s patients rely on Medicaid.

Everett mayor candidates focus on affordability, city budget in costly race

As incumbent Cassie Franklin seeks a third term in office, three candidates are looking to unseat her.

Everett
Judge sentences man, 73, for intending to have sex with ‘teen’ in Everett

The Arizona man sent explicit images to an agent posing as a 13-year-old. Investigators found images of child sexual abuse on his phone.

Community members gather for the dedication of the Oso Landslide Memorial following the ten-year remembrance of the slide on Friday, March 22, 2024, at the Oso Landslide Memorial in Oso, Washington. (Ryan Berry / The Herald)
The Daily Herald garners 6 awards from regional journalism competition

The awards recognize the best in journalism from media outlets across Alaska, Idaho, Montana, Oregon and Washington.

State’s draft of climate action plan open for public comment

Residents can submit public comments or climate-related stories online through Aug. 22.

The Edmonds School Board discusses budget cuts during a school board meeting on Tuesday, April 15, 2025 in Edmonds, Washington. (Olivia Vanni / The Herald)
Edmonds school board approves 2025-26 budget

After facing an estimated $8.5 million shortfall earlier in the year, the board passed a balanced budget Tuesday.

A wall diagram shows the “journey of the ballot” at the new Elections Center on Tuesday, July 9, 2024 in Everett, Washington. (Olivia Vanni / The Herald)
County Auditor: No need for feds to meddle with state or local elections

Garth Fell’s comments were in response to a report of Justice Department mulling criminal charges against election officials.

Edmonds Police Chief Loi Dawkins speaks after the city council approved her appointment on Tuesday, July 8, 2025 in Edmonds, Washington. (Olivia Vanni / The Herald)
Edmonds City Council confirms new police chief

Assistant Chief Loi Dawkins will begin in the role Aug. 1. She has more than 23 years of law enforcement experience, including three years in Edmonds.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.