Figure 1 |
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| (a) Ripples on the underside of river ice exposed by surface melt (courtesy of G. Ashton). |  |
| (b) Rogen landscape, Boyd Lake, N.W.T., Canada |  |
| (c) Hummocky terrain including Rogen landscapes, Stettler, Alberta, Canada. Note that the original air photograph is enhanced by infilling depressions with black ink, as though they are filled by water. |  |