Popular Science: The Jatunraju Glacier – lying and waiting?
The Jatunraju glacier is situated in the central part of the Cordillera Blanca Mountains in the Andes in Peru. It is one of the most glaciated mountains in the tropical zone but almost all the glaciers are receding. Scientists have investigated how the glacier has changed and moved during the last decades. These movements were observed by old geodetic measurements, aerial and satellite images and topographic maps.
Perón Lake is the one of the biggest in the region and it is dammed by the glacier. The lake is 10 000 –
13 000 years old. The glacier got larger in the recent Little Ice Age lasting until the end of the 19th century. Now we can observe the moraines, material transported by the glacier. The lake was evaluated as dangerous and thus some reduction of the water volume was worked out in the eighties.
The glacier lies at an altitude of 4100 – 5400 metres above sea level. The movement of the glacier was analysed from satellite images and is most significant in the middle part, which is covered by a several-metre-thick layer of debris and the glacier is beneath it. The debris is transported to the lower parts of the glacier. Many supraglacial lakes are created in the active zone. They are made by the thaw. These small lakes are volatile and they can become empty very quickly. This has an effect on the relief; it creates typical holes and tunnels. The lower part of the glacier is melting and subsidence is obvious. The glacier is changing into a glacigenic rock glacier there. It contains almost all debris with a lower portion of ice, often in the form of ice cores.
To sum up, the stability of the glacier should not be influenced by recent changes and Perón Lake should also be stable if its surface does not rise. Furthermore, thanks to increasing temperatures there will likely be a shifting of the rock glacier and the authors also expect a shift of the related processes.