The grey stripe down the middle of the glacier is called a medial moraine. It is formed when two glaciers flow into each other and join on their way downhill.

沿冰川中部而下的灰色条纹被称为中碛，它是由于两条冰河在下坡时汇合在一起而形成的。

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Crossing a medial moraine, we reach a pothole in the ice with a stream plunging into it.

BBC: The perfect trip: Switzerland