BERNHARD EDMAIER / SCIENCE PHOTO LIBRARY BERNHARD EDMAIER / SCIENCE PHOTO LIBRARY
Ogives. Aerial view of a glacier showing its annual growth curves, or ogives. These convex curves point towards the end of the glacier, as the sides move more slowly than the centre. They are made up of a series of raised bands where the summer warmth melted some of the surface ice. When it re-freezes in the winter, it is darker because it accumulated dirt. Winter growth, however, produces only white areas. The darker areas are more efficient at absorbing the Sun's heat, and partially melt, leaving shallow troughs beneath the crests. The dark bands at right and upper left are made of rubble carried by the glacier. This is the Gilkey glacier, Alaska, USA.
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