The Anatomy of a Glacier
Above, you can see Cerre Torre, a new mountain created in the last ice age, with Glacier Grande at its foot. The lake providing the reflection has been created by the ice sheet's melting waters, and formerly was the bed of the glacier in previous eras.
Walking on a glacier can change your view of water (don't forget to sign up for the Live Earth Dow Run for Water). An important fresh water reserve, the Southern Patagonia Ice Field is the second largest extrapolar ice field in the world, and has been dubbed a global resource by UNESCO. While touring the glaciers of Patagonia last month, I did such a walk, and received an education on these shrinking resources.
When you see a glacier in its various stages moving towards the inevitable lake that awaits its melting waters, you are stunned (In the picture above, you can see me about to walk Glacier Grande's ablation zone). I literally sat, watching several glaciers, poised for the crack of ice, the calving of their walls as they fell into the water.
The part most people see is the ablation zone, where net loss occurs. In these areas, you see the ice flows falling or floating away from the glacier. It is also where you can see the greatest effects of global warming.
In the above picture of Glacier Grande, you'll see several notations that highlight the glacier's melting process over the past 25 years:
- The section marked A represents the current glacier wall, 30 meters above the water surface.
- B is a granite formation uncovered by the glacier, which is more than 40 meters high in points. This is also where the glacier wall was located approximately ten years ago.
- With C we see where the glacier wall was 25 years ago. Global warming has had a significant impact on Glacier Grande.
- D shows you sediment lines, depicting how high the glacier has been in past eras.
- The ice floes depicted by E where originally part of the wall (A), and have calved. These mini icebergs were caught by the granite formation and eventually either melt or make their way into the larger lake.
- F represents the larger ablation zone.
If you participate in a glacier walk you can see incredible ravines caused by glacial melt, shrinking and growing. The fracture zone occurs right before the mouth of the glacier where melting occurs. The constant creeking, the deep ravines, the imminent danger, and the fact that the valley you are walking in was carved out by an older form of the very same glacier reminds you of the great power water posesses.
Walking a glacier can be a surreal experience, but can also be quite dangerous. In some cases the water moves in torrents, and carves massive falls and dangerous ice caves.
Make sure you hire a guide who can show you how to do it using crampons, picks, and other equipment. In our case, we had three tour guides who helped ten of us. Believe me, we needed them. There were several dangerous bridges that could have yielded a 45-50 meter drop into the freezing lake water under the glacier.