Glacier National Park - Glaciers and Symphonies

Glacier's Glaciers
After the rocks settled into place, the land gradually became eroded into soft contours. Pinnacled peaks were transformed into gentle domes, thickly wooded forests paraded up the slopes, and twisting streams etched V-shaped valleys into the mountain faces like wrinkles earned through time. Although these were peaceful times in the mountains, it was the proverbial calm before the storm. Over the next 3 million years, the land was gripped by tons of thick, steel-blue glaciers -- groaning, thundering monsters so powerful that they slashed rounded peaks into razor-sharp ridges, barreled narrow troughs into wide, sloping valleys, and dug deep canyons where none had been before. At least four times glaciers overspread the land, and then retreated. Lakes and forests developed in each intermission, only to be destroyed in the next onslaught.

Great rivers of ice flowing downhill, glaciers claim and rearrange whatever lies in their way. The Ice Age glaciers followed the path of least resistance -- the V-shaped glens -- and widened them into graceful, U-shaped valleys. Where the ice was thickest, it gouged long, deep basins into the land. Glaciers are movers as well as bulldozers; they carry rocky debris as they forge along. When changes in climate caused the glaciers to halt, they dropped some of their load at their downstream ends. These massive piles of rock, technically known as terminal moraines, dammed meltwater from the glaciers, and the area became generously sprinkled with such sapphire-blue bodies of water as Lake McDonald, the park's largest lake. The ridges that line its sides are also moraines: lateral moraines.

Unfinished Symphonies
Hundreds of smaller ice rivers -- tributary glaciers -- flowed into the mail glaciers, and each etched the mountains it touched with a different hand; rather than being identical, the mountains lining the valleys are distinctly different in contour. Because the tributary glaciers could not excavate as deeply or as rapidly as the channels into which they flowed, some were stranded mid-mountain when the glaciers retreated -- stopped in the act before they were finished with their work. Today these unfinished valleys, their heads usually cradling deep, bowl-shaped lakes called tarns, hang above the U-shaped valleys left by the larger glaciers. From the tarns, water flows down the hanging valleys and tumbles over stony staircased benches or falls free over sheer cliffs to reach the valley floor. Hidden Lake, an exquisite tarn tucked away in a crook of mountains near Logan Pass, is so snugly recessed in its rock setting that it looks like a jewel fitted to its mounting. Water leaving the neck of this narrow bowl plunges a breathtaking 2,600 feet into the Avalanche Creek basin. A drop of 500 feet more takes the roaring water to the McDonald Valley.

Sometimes more than one glacier formed on a mountain, and each traveled along a separate path. When two glaciers moved down opposite sides of the mountain, they nibbled away at the rock between them until only cleaver-sharp peaks and serrated ridges, called arêtes, remained. The Garden Wall is such a remnant. At other times, glaciers completely wore away the peaks and ridges, creating the graceful, saddle-shaped passes that connect many of Glacier's mountains.

When three or more glaciers attacked a mountain, they hewed a pyramidal or square-sided spire known as a horn. The park's mountains are a herd of such stony horns -- from Ahearn to St. Nicholas, Wacheechee to Thunderbird, Kinnerly to Little Matterhorn. (The "big" Matterhorn, which straddles the border between Switzerland and Italy, was formed in the same way.)

In the park more than 50 glaciers are still at work today, carving and shaping the landscape, like artisans who continually tinker with their work. But these are not the same sculptors that were active during the Ice Age; they are new ones, born about 4,000 years ago during a widespread cold snap. Inching along at a snaillike pace, our modern glaciers may take a year to accomplish what their ancestors easily managed in just a few hours. Sperry, the biggest glacier, progresses about 30 feet a year -- token whittling compared to the heavy industry of the past. To visit one of the glaciers, however -- to see the enormous crevasses that yawn open late in summer, to enter an ice cave spewing milky meltwater, to step on the living ice -- is to bring alive the memory of those monsters that trod and tore the land so long ago.