A snow pit shows off the season-by-season stratigraphy at the West Antarctic Ice Sheet Divide. Behind this wall of snow is open air, which allows the sun to peek through the various layers of snow. The uppermost dimmer layer is snow from last winter, the bright layer in the center is last summer, and the dimmer layer at bottom is the winter before that.

The ice cores pulled up at WAIS will be dated by counting back these seasonal layers as if they were tree rings.