A climber crosses a dangerous crevasse.


On the Move A glacier doesn’t flow smoothly. T e middle moves faster than the bottom and sides. T e diff erent speeds can crack the ice. T ese cracks are called crevasses. Some of these cracks are wide and deep. A thin crust of snow can cover a


crevasse. T e snow can’t hold much weight, though. If climbers step on it, they can fall through. Koppes once saw this happen. She


and her team were in a helicopter. Her partner leaned out. He poked the snow with a pole. It seemed firm. He jumped out. T e snow gave way. He started to fall. Luckily, Koppes was holding on to his safety rope. She pulled him to safety. Today, Koppes and her team roped


themselves together. If someone falls, the team can help.


20 NATIONAL GEOGRAPHIC EXPLORER


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