On the next to last day, we got into the tiny rented Chevrolet Classic and drove from Mendoza, the third-largest city in Argentina, toward the border with Chile. We wanted to see Aconcogua, the tallest mountain in the Western Hemisphere, the tallest mountain outside the Himalayas. There’s a small visitor center near the base, with a short walking trail that provides views of the peak, and a staging area for people who are going to try to climb to the summit. The mountain was beautiful and the half-day we spent wandering around the little park was splendid, but getting there turned out to be more interesting to me.
The road wasn’t bad—a bit narrow and steep in places—but the view was beyond spectacular. The highway follows the Rio Mendoza, a narrow, fast-moving river that arises in the glaciers near Aconcogua and delivers its muddy water down through the Andes to the deserts below. The Andes were pushed up—are being pushed up—by the subduction of the Nazca Plate, which carries the floor of the southern Pacific beneath the South American Plate. The mountains are young and jagged, and unlike any mountains I’d seen before, nearly naked. Look at Pike’s Peak, or any of the Rockies, and the entire base of the mountain is clothed in a swath of conifers that soften the look and obscure the structure. The Andes are different. Aside from a dusting of tiny bushes near the bottom, and a small cap of snow on the highest peaks, the Andes are geology laid bare.
I rode in the back seat of our car and craned my neck to try to see the mountaintops. The sky was clear and sharp and the sun beamed down. We stopped every so often to take pictures. The air smelled of creosote bush and other desert plants. All of us were biologists who had worked in the North American deserts, and we struggled to match the unfamiliar plants to those we knew from home; some were cactuses and mesquites, but others were completely new to us.
At each stop, I was impressed by how unrelentingly huge and empty the mountains were. There was almost no animal life, and the plants were sparse and small. It vaguely reminded me of the Sierra Madre Occidental in Mexico, except that the mountains were twice as tall. The strata of the rocks were plainly visible, all the way up the mountains, but they weren’t even or laminar. Instead, the layers were twisted and bent by the pushing-up of the mountains; in places it was clear that giant columns of rock had even been inverted in a manner that spoke of incredible violence, but violence that had taken tens of millions of years to accomplish. That was the message of the Andes—time, time, and more time.
The stunted shrubs around the bases of the mountains were probably three or four times older than me. They grow slow, and live long. I stood beside the road and looked up at hundreds (thousands?) of layers of rock, each one of which represented thousands (tens of thousands?) of years of sediment drifting to the ocean bottom. It was on the other flank of the Andes that Darwin found the rocks that supported his friend Lyell’s ideas on the age of the earth, but that’s not what made Darwin a genius. You’d have to be blind or stupid to ride through the Andes and not understand that the earth is an old, old place.
After our day on Aconcogua, we rolled back down Ruta 7 toward Mendoza, alongside the river again. In places, the river had dug deep canyons in solid rock, leaving cliffs a hundred or more feet high. How many eons does that take? Between the road and the mountainside, an abandoned narrow-gauge railroad rusts into ruin, disappearing at places underneath talus rockslides. A steel bridge is covered by rocks, looking as if it has partially melted into the mountain. “The mountain is taking it back,” one of my companions said, and I agreed with her. The earth takes it all back.
