Lathrop Glacier on Oregon's Mt. Thielsen Has Disappeared, But It Could Come Back: Expert

Oregon's smallest and southernmost glacier has disappeared, but could reform if humans stop contributing to climate change, experts said.

Lathrop Glacier was located on Mt. Thielsen, an extinct volcano in the Oregon High Cascades. Oregon Glaciers Institute President Anders Carlson said it had an area of less than 0.002 square kilometers, or less than half of a football field.

He said it was in a steep area, describing it as "a very vertical water slide at a theme park, basically."

The exact date of the glacier's disappearance is not known, but the Oregon Glaciers Institute knew it was gone by 2020 when employees visited the site.

Carlson said the most likely reason for Lathrop's vanishing is climate change, theorizing that the summer of 2015, which was the hottest recorded summer in the Cascades, had a great impact on it.

However, Carlson also predicted Lathrop could return if climate change begins to slow. Portland State University Professor Andrew Fountain added that it's not unheard of for small glaciers to disappear one year and reappear another.

"We could start cooling down again if we could reduce greenhouse gases in the atmosphere," Carlson said. "The state wants to grow glaciers, and it wants to have snow."

Mount Thielsen, Oregon
Experts say Lathrop Glacier on Mount Thielsen has disappeared, but could come back if humans stop contributing to climate change. Above, a view of Mount Thielsen in Oregon. Stock Image/Getty Images

The glacier had probably been in existence hundreds, maybe thousands of years.

"Since the Romans or something like that, there had probably been some kind of glacier ice formed on that area there," Carlson said.

But it wasn't discovered until 1966 when Ted Lathrop (pronounced LAY-thrup) spotted it on a hike.

Lathrop died in 1979, but The News-Review spoke to his nephew Ralph Nafziger, who returned with his uncle to the Lathrop Glacier in 1968 and returned again many times in the years after that.

Nafziger worked as a geochemist for the U.S. Bureau of Mines in Albany until 1996. He also enjoys hiking.

"I've climbed mountains all over the world and most of them had glaciers on them," he said.

The year before he spotted the glacier on Mt. Thielsen, Lathrop had served as the resident physician on an expedition to the Juneau ice fields and learned something about them.

So when he looked down the mountain's steep north slope, he was pretty sure that was what he was seeing.

Nafziger, Lathrop and a U.S. Forest Service district ranger took a closer look in 1968.

They followed the Pacific Crest Trail, climbed up to a ridge and looked right down.

"It was a sheer drop, almost 90 degree drop. We were all young. We rappelled down to the ice on the glacier," Nafziger said.

A glacier must be, by definition, moving ice. So they set up some stakes to measure the movement.

The next year they returned and found there was movement. But all their stakes had slid down and were lying in a pile at the bottom of the glacier.

Since the glacier was clearly too steep to measure its exact movements with stakes, Nafziger resolved to return regularly and photograph the glacier to record its changes.

"We had to get there just at the right time, because if we got there too early there was still snow to be melted off the ice, and we couldn't get an idea of how big it was. If we got there too late, then the new snow started," he said.

Some years there was new snow as early as Labor Day. Other years it was the end of October.

He learned that over time, the glacier was shrinking. In 2016, the last year he saw it, there wasn't much of it left.

Nafziger can't climb anymore for health reasons, so he never saw it after that.

The exact date of Lathrop Glacier's demise isn't known. But in 2020, when the Oregon Glaciers Institute visited the site again, it was gone.

The Cascades have grown significantly warmer overall thanks to climate change. The summer average has risen between 2 and 3 degrees Fahrenheit since the early 1990s.

"It's dramatic warming that is not being seen at lower elevations," Carlson said.

As it gets warmer, the snowpack melts out earlier.

Then came the summer of 2015. It was the hottest summer on record in the Cascades.

The extra warm summer was due in part to it being an El Niño year.

Then, too, there was the Blob, a "weird warm water mass" off the coast of Oregon that both warmed the air and blocked the snow, Carlson said.

That year had the lowest snowpack ever on record.

With Lathrop's disappearance, the state's southernmost glacier is now the Crook Glacier on Broken Top Mountain west of Bend.

While Lathrop Glacier has disappeared, this doesn't have to be the end of its story.

Fountain's lifelong love of snow and ice turned into a 40-year career studying glaciers.

He said small glaciers like Lathrop often disappear one year and reform in another.

"I'd be very surprised if it hadn't happened before. On a good snow year I could see it coming back," he said.

The Associated Press contributed to this report.

mt thielsen, glacier, climate change, mount thielsen
Oregon's smallest and southernmost glacier has disappeared, but could reform if humans stop contributing to climate change, experts said. Above, Mount Thielsen in Oregon is surrounded by forests in 1997. © CORBIS/Corbis/Getty Images