The face of Perito Moreno Glacier resembles a colossal fortress, its jagged spires of ice towering about 200 feet above a lake dotted with icebergs.
It is Patagonia's most-photographed glacier, yet as we stand before it I realize that images can only begin to capture its grandeur: the panorama of ice that fills our field of vision, the thunderous cracking sounds that echo from within the glacier as it slowly shifts and advances.
My wife and I have come with our two children to southern Argentina to see and experience its glaciers and mountain landscapes. We are among hundreds of visitors who stand watching from a network of raised walkways on a slope facing the glacier.
Suddenly, the cracking sound grows louder and a cascade of ice tumbles down the sheer snout of the glacier. A column the size of a 20-story building slowly begins to tip away and collapses in a giant splash about 500 yards from where we are standing.
Then other pieces break off and fall in a series lasting more than a minute, leaving a dozen new icebergs floating away.
"Woo-hoo!," my 6-year-old son shouts. "It's just like sand."
The calving glacier reminds him of sand cascading down a steep dune he had climbed a few days before on the Argentine coast.
Perito Moreno is among the most accessible large glaciers and remains relatively intact even as glaciers all over Patagonia have been retreating in the past few decades.
During that trip earlier this year, we all stood gazing at the glacier, leaning on the wooden railing and silently waiting for the next ice fall. Some people lifted cameras now and then, while others sat quietly on benches taking in the view.
Along the section of glacier that had just calved, the newly revealed wall glowed deep blue, indicating the ice had been tightly compressed during its long journey down the mountain slope.
We had heard and read that waiting for a big ice collapse could require patience, so we felt fortunate to have witnessed the spectacle within minutes of arriving. We lingered on the walkways, enjoying the cool air and seeing the glacier from different angles.
Light rain began to fall, and we retreated to a snack bar for hot chocolate.
The next day, we took a boat tour of the glaciers that border Lake Argentino.
There are dozens of glaciers in the area fed by the Southern Patagonian Ice Field, which blankets a wide swath of the Andes between Chile and Argentina. Huge quantities of meltwater flow into Lake Argentino, and then down the Santa Cruz River to the Atlantic.
We started at the port of Punta Bandera and set out aboard a catamaran carrying nearly 200 people. The wind was very cold, so we started out inside the cabin, then put on wool hats and scarves and went out on deck for a better view as we approached several icebergs glistening in the sun.
The icebergs were a gemlike radiant blue, contrasting with the charcoal-colored mountainsides behind them. The ice had been sculpted by sun and lake water into fantastic shapes topped with spikes and curves.
As we headed toward Upsala Glacier we encountered more and larger icebergs, and the boat stopped once we faced a barrier of floating ice. Some passengers posed for photos at the boat's railing with craggy masses of ice floating behind them. I wished I could get a glimpse from the air of the many icebergs floating between our boat and the glacier.
Guides announced over the loudspeaker in Spanish, English and French that Upsala Glacier could be seen in the distance. They didn't mention that it has shrunk dramatically over the past century, nor did they discuss how the glaciers have fared overall in the face of global warming. I wondered how quickly climate change might eat away at these majestic giants.
I later learned that according to a recent study by British and Swedish scientists who analyzed about 350 Patagonian glaciers, all but two of the glaciers have receded significantly since the late 1800s, and have been shrinking at a faster rate during the past three decades.
Still, Patagonia's mountain glaciers are so colossal, and fed by so much snowfall each winter, that scientists believe they are in no immediate danger of vanishing in the coming centuries.
"Those glaciers aren't going to disappear, that's for sure. They might get smaller, but they're not going to disappear," said Neil Glasser, a British glaciologist and one of the authors of the study, which was published in April in the journal Nature Geoscience.
Elsewhere in the park
Motoring on in the lake, we soon reached smaller Seco Glacier, which is aptly named "dry" and has been in retreat. On the slope below the foot of the tear-shaped glacier, a large, brown expanse of exposed rock outlined by a dense forest marked the line where the ice once extended.
Several icy peaks above were partly bare rock with deep, wavy grooves carved by the scouring ice.
We moved to the bow as the boat neared the Spegazzini Glacier, a steep, dramatic icescape that curves down a mountainside and ends in the lake. Another boat that sailed close to the glacier was dwarfed by its ice cliffs.
Our boat slowed down and stopped, and two crewmen tossed a rope over the bow and lassoed a briefcase-sized chunk of ice. They broke off a small chunk with an ice pick and passed it around.
My son held the sliver of ice for a moment, grinning, and handed it to a smiling couple next to him, who then passed it on to others.
After two days visiting the southern part of Los Glaciares National Park near El Calafate, we set out in a rental car for its northern end: the town of El Chalten and scenic Mount Fitz Roy.
There were few cars on the two-lane highway, and several groups of cyclists passed in the opposite direction as we sped through the treeless landscape between Lake Argentino and Lake Viedma.
After driving for about 20 minutes, the dramatic view of Mount Fitz Roy appeared on the horizon under a clear sky, its sheer granite faces flanked by smaller jagged peaks. Measuring 11,072 feet, the mountain is a world-class destination for trekking and climbing. We were delighted just to see its rugged beauty.
We stopped several times to look and take pictures of the mountain, being careful to park facing the wind. An employee at the rental car agency had warned us that in this area heavy gusts have been known to rip car doors from their hinges.
We laughed as we fought the wind to walk just a dozen steps at a roadside stop near El Chalten, taking photos of each other as the gusts blew our hair in all directions.
The next day, the weather was calmer near the base of Fitz Roy, and we hiked along streams and through forests where grass glowed in patches of sunlight among the bushy lenga trees.
Our infant daughter rode along in a backpack carrier, and our son enthusiastically led the way with a walking stick he found, jumping over rocks in the path.
He asked if we could hike up close to one of the glaciers we could see in the distance on the side of the mountain.
On the last afternoon of our stay, the weather was cloudy and drizzly, and we walked farther along the same trail toward Fitz Roy. After more than an hour of hiking, we stopped at a clearing. The mountain above us was shrouded in clouds.
Below the mountain we could see another glacier, veins of blue crisscrossing the white mass.
Posing there for a photo, my son smiled and raised his arms triumphantly with the glacier towering behind him.
Even from a distance across that mountain valley — and now from a distance of several months — the glaciers of Patagonia have left a powerful impression on us.