BANFF, Canada — If you were offered a cup of water that had been languishing for at least 150 years, you probably would refuse to drink it. And who could blame you?
Yet in Alberta province, hundreds of thousands of people pay each year just to get close for a sample.
This pristine water is meltwater from Athabasca Glacier, one of eight glaciers spawned by the Columbia Icefield that straddles the Great Divide between Alberta and British Columbia.
Falling to earth as snow between 150 and 400 years ago in the pre-pollution era when bison roamed the plains, it is some of the purest water on earth.
An icy finger of probably the largest accumulation of ice and snow south of the Arctic Circle, the Athabasca Glacier is one of only three visible from the spectacular Icefields Parkway Highway 93.
Winding through the Rocky Mountains and some of Canada's most exquisite scenery, this 143-mile highway connects several of Western Canada's most popular attractions, including Jasper, Lake Louise and Banff, all of which are within a leisurely day's ride of the glacier.
The Athabasca is the only glacier where rides are offered onto the moving sheet of ice in specially built snow coaches. Visitors can stand on this wonder, which is still in its formative process. Just being surrounded by glistening snow-covered mountains under a brilliant blue canopy makes the excursion worthwhile.
Resembling a gigantic dollop of marshmallow creme, this shimmering tongue of ice slides imperceptibly but irrepressibly down the sides of a slate and limestone sundae.
But don't except to feel the motion. Creeping at the rate of about 75 feet a year, movement boils down to a scant one-tenth of an inch an hour.
The excursions begin with a shuttle ride from the National Park Interpretive Centre to the snow coach terminal at the glacier, where guests embark on one of the world's most unusual rides aboard a massive 56-passenger snow coach.
Navigating down a steep 300-foot moraine and looking like a colossal caterpillar on a hill, the coach lumbers out onto the ice.
A moraine is a formidable pile of debris left in recent decades by the receding glacier. While descending, the guide will point out other glacial features, such as crevasses, meltwater streams and a gleaming Mt. Andromeda.
Visitors will also be treated to a commentary of sometimes staggering facts about glaciers. Among them:
--"This peaceful-looking glacier took untold thousands of years to form and is constantly changing, even as we ride on it."
--"Trilobite fossils more than 500 million years old, found here, give evidence that these 9,000-foot peaks were once part of an ancient sea."
--"Covering more than 150 square miles, this Gargantuan ice cube represents 11% of the earth's trapped fresh water."
--"The ice you are about to walk on is more than 1,000 feet thick, equal in height to a 70-story skyscraper."
--"The splendor of the surrounding scenery is incomparable--cobalt blue sky jabbed by staccato peaks of snow and massive quantities of ice."
But beware the metering system of most modern cameras. They will be fooled by all that glare, and will thus underexpose to compensate, turning the sparkling white glacier into a dull-gray heap. The best way to correct is to purposely overexpose your photographs.
Handing out a paper cup with an admonishment not to litter the glacier with it, guides offer a sample of water from a stream gurgling with evidence of a cleaner environment long ago.
The water is distinctive because it has no taste--no chlorine, no salts, no chemicals. Nothing but pure water.
Part of the fun of venturing out onto the ice is the snow-coach. Owned and operated by Brewster Transportation and Tours, these 2 1/2-ton behemoths take 18 months to build and sell for a whopping $368,000.
That's a hefty price to pay for a vehicle with a top speed of 15 m.p.h. on the ice and 38 m.p.h. on the highway. Hardly a threat at the Indianapolis 500, these lumbering titans seem perfectly matched with the slow pace of geological time that shaped their home turf.
According to Andrew Whittick, Columbia Icefield operations manager for Brewster, there are only 11 vehicles of this type in the world, all here at Columbia Icefield.
They have had various uses, including the Olympic ski hill and assorted parades, but Whittick's favorite was a California promotion in which it ran along the beach.
"They make a great dune buggies," he said. "Not speedy but definitely impressive."
And just in case you are tempted to complain about changing a flat tire, consider this: Measuring 66 by 43 by 25 inches (almost four times the size of regular tires), these Goodyear giants cost about $5,000, but for that price they'll throw in the wheel.
Operating every day from 9 a.m. to 5 p.m. from May to October, the snow-coach tours cost $14 for adults, $7 for children and take half an hour.
Busing out on the ice is not the only way to visit the glacier. The most energetic and adventurous can arrange ice walks with guides who point out and interpret glacial features.
Beginning at the toe of the glacier, hikers can seek out caverns, crevasses and subglacial streams. Some of the caves have ceilings that are more than 100 feet from the floor and resemble gigantic, blue, ice carvings.
The walks last three hours and leave at 12:30 p.m. daily except Sunday; adults $15, children $7. Longer walks are available. Contact Peter Lemieux, Athabasca Glacier Icewalks, Box 2067, Banff, Alta., Canada T0L 0C0.
For more information about snowmobile tours on the Athabasca Glacier, contact Brewster Transportation and Tours, Box 1140, Banff, Alta., Canada T0L 0C0, (800) 661-1152, or Travel Alberta, 333 S. Grand Ave. Suite 3535, Los Angeles 90071.