The Mendenhall Glacier takes about 80 years to complete the journey from its mountain source to the modest-size lake it has created within Juneau's city limits. It starts out a mile thick at the top and ends a mere 150 feet thick at the face or terminus.

Documented as receding for at least 200 years, the Mendenhall has, since 1934, pulled back a mile from the park Visitor Center to its present position. As of 1999, this formidable river of ice was retreating at 60 feet a year; today it is galloping backwards at 200 feet a year!

The 1,500 square-mile Juneau Icefield feeds and fosters 38 major glaciers, including the uncommonly-accessible Mendenhall. Despite its apparent permanence, the Icefield is only 3,000 years old, a mere tick tock on the geologic clock. Even if global warming has indeed triggered a glacial demise, as many scientists believe, visitors to Juneau still have plenty of time to take in this wonder of Mother Nature before the last ice cube floats across the lake.

I arrived at the NorthStar Trekking heliport in a complete state of ignorance. Not sure what one is supposed to bring along for a helicopter ride to the birthing end of a glacier, I had stuffed my day pack with city gloves, a crocheted hat, and extra sweater, as I donned hiking boots, jeans, sun glasses and a hooded rain jacket. Right off the bat, my daypack was replaced with a large multi-pocket fanny pack and clothing decisions were taken out of my hands.

"If you arrived in your pyjamas, we could outfit you!" owner Bob Engelbrecht made clear in the first couple of minutes as we assembled in the changing area stocked with clothing, boots and gloves to fit everyone from children to football players.

Being individually sized up for deep winter pants and hooded jacket, gloves, mountaineering boots, and wide blue gaiters on a warm Alaska summer afternoon seemed alien enough. However, the body harness, the trekking pole/ice pick, and the crampons made it clear that something truly uncommon for all of us was on the activity menu.

Scrambling into our assigned helicopter seats like a flock of ungainly Pillsbury doughboys, we each donned a headset to communicate with our pilot, Ken, and with other passengers during the 30-minute flight out of the Juneau airport. On a windless day with a nice balance of cloud and sun and headphones to drown out the sound of the rotors, we took to the air with no sensation of movement at all. My mind shot back to another flying first in my life, hot air ballooning over Turkey's haunting Cappadocia landscape. There too, I had been amazed by the perception that my flying machine was not moving at all.

We headed into the higher elevations of the massive Juneau Icefield, a virtual sea of snow, ice and towering charcoal-colored rock ranges on all sides of the helicopter. We soon locked in on the Mendenhall Glacier from its mountain top accumulation zone where up to 100 feet of snow may fall there in a season. Coming around in a circle that pointed us back towards Juneau, we began tracing the flow gradually downhill. It was quite impossible to get any sense of scale until we spotted a bright orange dome tent marking our touchdown area and tiny figures nearby who were obviously anticipating our arrival.

Glacier trekking is the closest sensation I ever expect to get to walking on the Moon. It is truly an awe-inspiring, timeless landscape that captures what glacier scientist, Dr. Maynard Miller, describes as a "sense of the eternity of the universe around you".

Totally at ease in this strange white world, our guides, Bill and Andy, helped us out of the helicopter and stabilized our first steps on the snow-packed surface. We stood on a river of ice still 2,200 feet thick at this midpoint in its flow to the coast. A moderate breeze added to the wind chill. Gratefully zipped up to my chin in a thick hooded jacket and wearing snow pants and ski gloves, I momentarily pondered Andy's choice of glacier wear - a short sleeved cotton shirt, no head gear, and a thin sleeveless fleecy. He was smiling and his arm actually felt warm.

Before we could perform a perilously ungraceful backflip onto the glacier, each of our earlier-selected crampons were strapped to our boots, now each bristling with a dozen razor-sharp metal triangles that looked like medieval torture instruments. If you kicked someone or tripped over your own leg, blood would be drawn and possibly stitches required. Lessons in how to walk in these awkward but necessary grips were the first order of business, including how to trek up and down ice hills while maintaining a reasonably vertical position. It is harder than it looks.

One of our guides casually threw out an offer to do some rappelling down an ice cliff if anyone wanted to try this during our two-hour walkabout and discussion of glacier geology. I only recall two people out of six volunteering. I was not one of them. Still, somehow when we reached the appropriate cliff face, red faced and puffing yet invigorated by our efforts, and we looked back toward the speck-sized helicopter and orange tent in the distance, it seemed to be the shortest way, well maybe the only way, across the ice canyon that lay below our feet.

Hmmm, I thought …. So this is why the harness. Another first for virtually all of us, we rappelled one by one, awkwardly but triumphantly, to the canyon floor, cheered on by each other and our watchful guides. Is this what they had in mind all along? The last guide gathered up the secured rope at the top and literally ran down the cliff to join us. Well, maybe it wasn't quite as steep as it looked.

By the time we picked our way past a series of deep crevices (deceptively shallow-looking when filled with brilliant blue-green water), forded a few sun-melting streams, and urged our tired legs in the direction of the landing site, it was hard to believe we had only been walking around the glacier for two hours. Stuffing our faces and our pockets with energy bars and Gatorade, we bid goodbye to our guides and climbed aboard Ken's helicopter to complete the loop - an exhilarating ride above the Mendenhall Glacier right over its face, across the beautiful blue-green lake now laced with orange from the setting sun, and back into the Juneau airport.

NorthStar Trekking, www.northstartrekking.com, offers three levels of glacier experience, all including a spectacular 30-minute helicopter flight each way to the glacier landing site. Small groups encourage informative and security-minded exploration suited to each client's abilities and interests. Level 1 is a Glacier Interpretive Walkabout of one hour; Level 2 is more strenuous with a two hour hike on the glacier; Level 3 involves an extended four hour hike on steep terrain with some technical climbing. The Level 2 experience is described in this article, where all but one participant on our trek were between 50 and 60+.

Mendenhall Glacier information: www.fs.fed.us/r10/tongass/districts/mendenhall/. For those Juneau visitors not into helicopters or glacier trekking, there is good news! The face of this glacier is easily accessed on a paved road, just 13 miles from the city center by rental car, taxi or tour bus. It attracts hundreds of thousands of visitors a year, especially from the many cruise ships that spend a day in port. Allow plenty of time for the impressive educational Mendenhall Glacier Visitor Center which includes a large observation deck with telescopes, a museum, a theatre and bookstore, and for exploration of numerous well-marked walking loops, hiking trails, and salmon spawning streams in the area. Guided hikes are also scheduled by park rangers.

To learn more about Juneau, Alaska's Capital City, visit www.traveljuneau.com and www.JuneauAlaska.com.

Don't miss other colorful Alaska articles in the Travel with a Challenge permanent feature collection:
Discover the charms of Juneau, Alaska's isolated capital city.
Go small-ship cruising around Alaska's Inside Passage to enjoy wildlife and glaciers very close up.
Do an independent exploration of the remote Aleutian Islands by Alaska State Ferry.

Alison Gardner is a travel journalist, magazine editor, guidebook author, and consultant. She specializes in researching alternative vacations throughout the world, suitable for people over 50 and for women travelers of all ages. She is also the publisher and editor of Travel with a Challenge web magazine.
Email: alison@travelwithachallenge.com.