Posted on 07/15/2002 6:07:48 AM PDT by ValerieUSA
PARADISE RIDGE, Mount Rainier — They were a scientific odd couple, a perfect pair to make a breakthrough discovery. Geologist Dave Lescinsky knew glaciers, and his sure-footed mountain-climbing friend Tom Sisson had seen more of Rainier's oddities than most scientists. For years, it was assumed Mount Rainier's 25 mightiest glaciers chewed Washington's tallest volcano into its irresistibly craggy form.
As lava spewed from Rainier's gullet over the eons, the theory went, fiery molten rock gushed from the summit, filling the valleys. Then the rivers went to work, sluicing out new valleys, ultimately exposing Rainier's signature ridgelines.
Lescinsky and Sisson weren't so sure about that, and together they made a seemingly simple discovery that has led to a fundamentally new view of glaciers. They now believe the giant ice packs did far more in shaping Northwest volcanoes than ever imagined.
"Glaciers, as it turns out, are the architects of Mount Rainier," said Carolyn Driedger, a U.S. Geological Survey geologist. "They are the ultimate sculptors. Glaciers rule."
What the two geologists found in the late 1990s is that Rainier's intense lava never flowed into its valleys. The volcano's massive Ice Age glaciers wouldn't let it happen.
Over much of the past million years, ice filled Rainier's deepest valleys nearly to the brim.
Imagine not just frozen rivers but an enormous sea of ice cloaking the mountain. The glaciers snaked 65 miles or more into Puget Sound lowlands.
"When you're at Rainier, you have to put your Ice Age glasses on," says Sisson, a geologist with the U.S. Geological Survey in Menlo Park, Calif., who has spent a lifetime studying the Northwest's signature volcano. "People just don't really think about the landscape being different from what they see today."
What Sisson and Lescinsky, an assistant professor at the University of Western Ontario, discovered is this: Through the ages, in a series of massive battles, the glaciers and lava waged an epic war across the flanks of the 14,410-foot peak. And time after time, the ice won. The molten rock was no match.
Lava cascaded headlong into the glaciers — at that time 600 to 1,000 feet thick — and was super-cooled on contact. The lava began to search out the path of least resistance, flowing like red-hot spokes from the summit alongside the steaming ice packs. The lava began to build up, layer upon layer, forming massive ridges. Some fiery flows cascaded between glaciers, forming spectacular spires.
As time marched on, the glaciers slowly gave ground. They receded, exposing more and more of the valleys they once owned, as well as Rainier's newly formed lava cheekbones. The formations, for decades, intrigued geologists because the lava should flow down the valleys rather than atop high ridgelines.
Sisson had been dating the mountain's oldest lava flows and knew the most recent were only 40,000 years old. He figured they were too young to have flowed into the old valleys, hardened and then eroded away to create the steep canyons of today.
"If glaciers could cut canyons 600 feet deep in 40,000 years, there'd be no volcano at all," Sisson surmised.
In addition, the two men kept stumbling across something unusual. Across Rainier's muscular midriff, they found glassy volcanic rock and shiny, perfectly formed columns that show lava had cooled extraordinarily fast, as if by ice.
As a result, they now believe that glaciers — normally known for cutting into landscapes — can also violently redirect lava, even drive it upward to create new flanks of a volcano. And that's how Rainier's most famous hardened outcroppings — Paradise Ridge, Rampart Ridge and others — were formed, say Sisson and Lescinsky.
An icy conveyer belt
At the end of any summer, more snow and ice cover Rainier than all other Cascade peaks combined — about 34 square miles.
A glacier's movement is primarily caused by gravity. It rumbles like giant conveyer belts, shoving giant slabs of ice — sometimes in flowing waves inside the ice pack — downslope until it reaches the glacier's terminus. That journey from summit to river canyon can take 200 years.
On Rainier, glaciers move an average of a half foot or more a day. When they slide over cliffs, or the movement changes speeds, the ice splits, forming crevasses that yawn 100 feet deep.
And while some glaciers seem to move backward, as if beating a not-so-hasty retreat, it's actually an illusion.
"Glaciers don't defy the laws of gravity," said Driedger, the U.S. Geological Survey geologist. A glacier "retreats" when its head — the terminus — melts faster than its ice can move.
Each glacier responds differently to climate changes. All but one of Rainier's glaciers currently are receding, but on Nisqually Glacier — Rainier's sixth-largest and among the country's most studied — lag time after climate changes is about 10 years. And Nisqually is preparing to advance again.
"Rainier's glaciers are healthy and moving like yo-yos," Driedger said.
A day of discovery
For Sisson and Lescinsky, the ebb and flow of mountainous ice has proved a constant source of scientific inspiration.
Sisson still recalls the day he first grasped the fundamentally different theory on Rainier's glaciers. He was hiking across a wooded slope on Rainier when he came upon volcanic columns embedded in the ancient lava flow that forms Rainier's Emerald Ridge.
The columns formed neat stacks like cord wood, all shiny like glass, again as if ancient, hot molten lava flow had come in contact with ice.
But Sisson was standing on a cliff that dropped 800 feet into a valley. Beside those columns was nothing but big, empty air.
To the scientist, the meaning suddenly was clear: This empty space, at one time, had to have been filled by a glacier. And the lava would have to have flowed right beside it.
"Now imagine when the Ice Age ends," Sisson said. "You have big rock ridges made of lava, next to deep canyons that are glacial. But the canyons didn't get there because they were carved out. They were there because the glaciers kept the lava away.
"It was so compelling," he said. "At that moment, I knew."
This is what caught my attention. How can this be with global warming happening all around us? (/sarcasm)
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