The largest erratic in the United States is hiding in plain sight.
More specifically, in Lake Stevens.
The boulder, left behind during the Ice Age around 14,000 years ago, is affectionately known as the “Lake Stevens Monster.”
It measures 34 feet tall, 78 feet long and 54 feet wide. It’s 11 feet taller than the second largest erratic in the nation, the Madison boulder, in Madison, New Hampshire. Only the Okotoks erratic in Alberta, Canada, is bigger in all of North America — that we know of.
Geology isn’t really my thing, but standing in front of a rock the size of a house is really something.
I saw the “Monster,” and three others in Snohomish and Island counties in a single day, including those in Edmonds, Mill Creek and Langley. Finding the one on Whidbey Island proved to be a surprisingly fun adventure.
Erratics are rock fragments that were carried by glacial ice then deposited after the ice melted during the last glacial period. Many of them have traveled from Canada; others have origins as close as Deception Pass.
Though they can be as small as pebbles, the largest erratics are evidence that this area was once covered in ice thousands of feet deep. Puget Sound’s lowlands are covered with debris from that time period.
Dave Tucker, research associate in geology at Western Washington University, said we can’t see the process that brought the rocks to the area, but we can certainly see the aftermath.
“I think that’s what people like about them,” Tucker said. “The big ones are so big, and people wonder where they came from.”
Tucker’s blog, Northwest Geology Field Trips, explains how to find erratics in the Pacific Northwest. It also gives people the tools to be a rock expert for the day.
The Lake Stevens erratic, located on 83rd Avenue near Highway 204, was known to locals for decades, but its existence was never documented or reported to geologists. That was until 2011, when two Lake Stevens police officers took measurements and spread the word.
The monstrous boulder is in a tiny park in the middle of a Lake Stevens neighborhood. The Glenacres Homeowners Association maintains it.
It took me just a second to realize how it got its nickname. Standing at its base and looking up is like facing a cliff.
The erratic is composed of greenstone, a metamorphic rock that has undergone transformation by extreme heat or pressure. It’s the most common type of erratic found in the lowlands, Tucker said.
The rock itself could be 125 million years old. It was coarse and cold to the touch.
The Martha Lake erratic near Mill Creek was my next stop. It is easily found at Martha Lake Airport Park, next to a skate park and walking trails, at 200 146th St. SW., Lynnwood.
That one is 40 feet long, 18 feet tall and 15 feet wide, and also made of greenstone.
An interpretive sign in front of the rock explains what glacial erratics are, when glaciers covered the area and how they are formed.
Next I visited the Edmonds Way erratic, just off Edmonds Way. It’s smaller than its nearby counterparts at about 11 feet tall.
My last stop was to see the Waterman erratic, found in Langley not too far from where I live on Whidbey. Tucker called it the “Mother of all Erratics” before it was discovered that it is surpassed in size by the one in Lake Stevens.
If there’s one erratic I’d recommend seeing, it’s this one. I’m not just saying that because I’m biased — it’s one of the few in Western Washington that is only accessible by trail.
It takes about 15 or 20 minutes of hiking in Saratoga Woods (4228, 4246 E. Saratoga Road) to find it. That’s plenty of time to build up suspense.
I don’t usually go for hikes in the forest alone, but the excitement of finding the erratic on the trail kept me going.
About 10 minutes into the trek, I crossed an overgrown airstrip, now a dirt path people use for running, biking or cycling. The Waterman erratic is about 200 feet on the other side of the airstrip.
It was exhilarating and beautiful to see.
The late afternoon sun gleamed off the top of the gigantic rock. The forest envelops around it, seemingly giving it the spotlight. Far enough away from the hustle and bustle of traffic, nature is the only thing you hear.
Its sheer size — 38 feet tall and 60 feet wide — makes it look out of place.
If you have time, go check them out.
But there’s no need to rush. The rocks aren’t going anywhere.
If you go
Four erratics — in Lake Stevens, Martha Lake, Edmonds and Langely — are boulders that have been brought by glacial action to Snohomish and Island counties.
Visit Dave Tucker’s website at www.nwgeology.wordpress.com for directions. Others can be found in Coupeville, Duvall and Seattle.