Photographers are mourning the loss of an iconic Minnesota “sea stack” that welcomed visitors to Tettegouche State Park for years. It fell victim to a winter storm over the weekend, claimed by powerful wind-driven waves that toppled the precarious structure into Lake Superior.
The picturesque henge was “approximately eight feet in diameter, roughly, and probably about 20 feet high,” said Kurt Mead, an interpretive naturalist working with the park. “It had a few trees growing on top,” he said, which resembled a trio of Charlie Brown Christmas trees.
But the storm proved too much for the long-standing formation, which disappeared beneath the churning waters over the weekend.
“We had a major storm up here,” Mead said. “The city of Duluth is still not plowed out. With that came a lot, a lot, a lot of wind and waves.”
Silver Bay Municipal Airport, which has the nearest observation station to Tettegouche, recorded a 32 mph wind gust Saturday afternoon. But “that [station’s] probably a little too sheltered,” said Linda Engebretson, a meteorologist at the National Weather Service in Duluth.
“On land, the wind drops rather rapidly,” said Engebretson. Higher winds are likely to have occurred over the water. The Minnesota Department of Transportation measured a 47 mph gust farther south along Route 61 near the coast.
“There was a very big snowstorm. We had blizzard conditions for about 10 hours here in Duluth,” Engebretson said. “We got 21.7 inches of snow, all over the weekend from Friday night through Sunday morning. Other places had [more], around 25 inches. But the real heavy amounts were very localized.”
Engebretson said the storm’s relatively compact but intense fury owed to a combination of intensified snow bands developing from cold air pouring over the lake’s relatively warm waters and the storm system’s “comma head.” That’s the region of wraparound moisture on the departing side of a low-pressure system that can often give rise to overachieving snowfall.
It wasn’t the wind that knocked the stack over, though. The waves did it.
“We had 20-foot waves right up here near the shore crashing against the pillar,” Mead said. “That took a toll. Finally it just went down.”
Engebretson’s office was forecasting wave heights topping 20 feet on Lake Superior. No wave height measurements were taken, however.
“The buoys … they pulled them out two weeks ago,” Engebretson said, referring to the devices used to measure wave height. She explained that ice accretion during the winter months can weigh down or even sink the buoys.
Surprisingly, the sea stack that was destroyed by the waves hasn’t been a sea stack for long. A decade ago, it was an arch connected to the main lakeside cliff. Then that collapsed.
“In 2010, we had the same kind of mourning process,” said Mead, who laments that the same process is unfolding again. “Now even the sea stack that once supported [the arch] is gone, and it’s really hitting people deeply in ways I didn’t expect. It’s all I’ve been seeing for several days now.”
Similar disappointment was felt across the Granite State in 2003 when New Hampshire’s “Old Man of the Mountain” collapsed.
Minnesota’s arch had a life span of barely a century. For a stone formation, that’s not all that long.
“If we went back in time about 1.1 billion years ago, lava flows made the rhyolite — the type of rock this was made out of,” Mead said. “Eons passed. We have a picture of this, what used to be an arch connected to the cliffside, in 1932, with just a few windows opening in the bottom.”
“Geologically, this is quite young, likely dating back 100 years or so. That’s when [the lake] probably opened up this sea arch” Mead said.
“The same forces that created it are what brought it down.”
Despite the loss, Mead said the park is still overwhelmingly beautiful and encourages people to explore it. “We have world-class cliffs, one known as Shovel Point; others that are 200 feet or more high that also draw photographers and sightseers,” he said. “The shoreline is one of our main attractions.”