After more than six weeks trawling the Peruvian Andes in search of palaeoclimate clues, our field team is visiting the last site, a potential calibration sites near Coropuna. The objective of that ongoing work is to refine the cosmogenic surface-exposure method for the tropics, thereby improving the precision of new and existing datasets.
Vanishing Tropical Glaciers
Team: Gordon Bromley, Kurt Rademaker, Matt Hegland and Gisela Winckler
Purpose: Sampling of glacier deposits
Start Date: June 19, 2011
From the Himalayas to the Alps and Rockies, mountain glaciers are rapidly melting. A sign of a warming climate, their retreat may also threaten hydropower and water supplies for cities below. To put current trends in context, scientists at Columbia's Lamont-Doherty Earth Observatory are studying rocks that record the ebb and flow of ice since the last ice age, over the past 20,000 years. They will travel the high peaks of the Peruvian Andes, including Nevado Coropuna, a 22,000 foot volcano. Other scientists will study pre-Columbian remains on the mountains. Geologist Gordon Bromley reports from Peru, while geochemist Gisela Winckler writes from the Lamont campus.
Our field team has set camp at 5045 m on the dusty slopes of Ampato, an extinct, ice-clad volcano in the Western Cordillera. This is the very mountain from which Juanita, the famous Incan ‘ice maiden’, was plucked back in 1995. The tents are clustered in the lee of a large glacial erratic and, now the clouds have cleared, the view is second to none, taking in the dry plains far below and myriad volcanic peaks in every direction.
After a busy few weeks in the Cordillera Carabaya, our field team has said goodbye to the snowy, tempestuous climate of the eastern Andes and is moving west to the desert of Arequipa. Here the mountains are massive, isolated volcanoes, many of which exceed 6000 m in elevation. In fact, Coropuna is the third highest mountain in Peru and certainly the most sprawling.
Our field team has acquired a dog, ¨”Mooch”. Walking back to camp yesterday, amid driving snow and fully laden with rock samples, there he was exploring what passes for our kitchen. Unlike most Andean dogs – ferocious beasts trained to keep geologists from harassing the livestock – this one is a cheerful soul, happy to hang around and be fed whatever is going, and always up for affection.
Thanks in large part to Matt, an undergraduate from Pacific Lutheran University in Washington, our field team now has more than sixty samples for surface-exposure dating. This is no easy feat, for collecting these samples requires a great deal of hammering on granite boulders with nothing more than a hammer and chisel. There are other ways of doing it, such as using small explosive charges, rock saws, or splitting wedges, but we find that good old-fashioned hammering is by far the safest way.
Each morning starts the same in the Andes: the frost is heavy on the insides of our tents and falls with the slightest movement, while the realization that it´s going to be a freezing exit from the sleeping bag is tempered by gratitude that the thirteen hour night is over. Yes, sunrise in the Andes is a momentous occasion each day, one that feels a million miles away from home.
After a very cold morning in Crucero, the sun burned off the clouds to reveal the black peaks of the Cordillera Carabaya to the east. There´s not so much snow left on the hills these days, just a few glacier patches clinging to the south faces of the highest summits.
This morning we left Arequipa and the comforts of the tourist trail, driving east across the puna towards the Andes proper. Our route took us along the newly constructed Caraterra Interoceanica – a highway linking the Pacific coast of Peru to ports in Brazil – and up to elevations of 4700 m. Along the way we passed the smoking Volcan Ubinas, Peru’s most active volcano, and the enormous inland sea of Lake Titicaca.
What a difference a day makes! We’ve said goodbye to the sprawling metropolis of Lima and now are happily settled in Arequipa – the White City. This name refers to the white sillar rock used in the construction of the old colonial city and which is in fact a pyroclastic deposit from the volcanoes towering above us. From our hotel room I can see the massive bell-shaped peak of El Misti (5800 m), the only active volcano of the group, and it’s looking particularly snowy this year.
18th June 2011 Lima, Peru Our 2011 field season is underway. After a full day’s travel from New York, we arrived in Lima, the capital of Peru. This sprawling city perched on the edge of the Pacific Ocean is home to more than nine million people and, after Cairo, is the largest desert city in [...]