start We turn eastward and fly away from the mountains.  The ice shelf is a  sheet of snow-covered ice as far as the eye can see. In places where ice is under stress, it forms large cracks known as crevasses. but for the most part the ice shelf is nearly featureless except for small wind ripples in the snow. Although the vast, often featureless ice shelf is an amazing sight, there is much more to be learned from our instruments than from looking out the window.