A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests and are carried by glacial ice, often over distances of hundreds of miles.
Who would think that we have a glacial erratic that is as big as a house right here in Lake Stevens?
Well, we do and it was found by Police Sergeant Craig Valvick while he was patrolling the bottom of the neighborhood off of 91st Dr. SE and 1st St. SE.
Valvick told Officer Matt McCourt about the huge rock, which he found in the small community park at the dead end, and the two of them started doing some research.
At home one evening, Valvick was browsing the internet and found the Northwest Geology Field Trips website. In an article titled “Whidbey Island Erractics” it stated, “The challenge is on, who can find a bigger erratic west of the Cascades?”
“From the road it’s not as impressive as when you get out and walk around it,” Valvick said. “I was pretty impressed with it.”
So, why did Valvick see something more than everyone else who had seen the rock?
“I just paid attention in geology class in high school,” he said. “I can’t believe I remembered anything from 22 years ago.”
After making some initial estimations, McCourt and Valvick decided to get a 100 foot measuring tape and take actual measurements. They were surprised to find out that their estimates were low.
The rock actually measures 210 feet around, is 20 feet high in the front and 34 feet high in the back. The face width is 78 feet. They decided to name it “Maximus Roximus”.
The next step was to contact a geologist. They found David Tucker, a Volcanologist and Research Associate in the Geology Department at Western Washington University.
Tucker, along with Donn Charnley, an Emeritus Professor of Geology at Shoreline College, visited Lake Stevens’ newly discovered geological find last Friday, July 8.
“I just think this is fabulous,” Charnley said.
Tucker is quite certain that the erratic came from the Vashon Glacier and is over 180 million years old.
“It most likely came from one of two places,” Tucker explained.
He feels it came from either the Deception Pass area or from Mt. Shuksan near Mt. Baker.
“I’m leaning toward Mt. Shuksan,” Tucker said. “I can imagine a rock like this falling onto the surface of the ice and sliding until the ice melted and left the rock in its path.”
There are two other, more well-known erratic in Western Washington, both on Whidbey Island—one near Langley, the other near Coupeville.
On Tucker’s website he begs the question, is the Waterman Erratic, near Langley, ‘The Mother of ‘em All?’ After visiting the Lake Stevens erratic, he has now named it the new reigning mother of erratics here in Western Washington.
On Tucker’s blog he explains exactly what the rock is, saying, “We determined that the rock is composed of greenstone, in places serpentinized. Greenstone is a low grade, metamorphosed sea floor basalt.”
Valvick and McCourt’s months of research paid off when Tucker announced that he thinks it is most likely the largest erratic around, giving Lake Stevens geological bragging rights.
Tucker just asks that if you visit the erratic at 23 - 83rd Ave. SE that you keep hammers or other tools off of it.
“If people want to see what the rocks look like, there are pieces all over the ground,” he said. “It’s a public treasure.”
For more information regarding local glacial erratics, visit nwgeology.wordpress.com.