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[Stockbild] Glacial folds. Aerial photograph of the folds in the Steller Glacier, Alaska, USA. The bands of colour are due to sand and dust from surrounding mountains, which settles on the glacier turing the ice grey. As the glacier moves, sharp folds are traced out in the ice. Most glaciers are currently receding, but several, notably those in Alaska, show regular surges that produce these patterns. (KEYSTONE/SCIENCE PHOTO LIBRARY/BERNHARD EDMAIER) === ===