This image shows rib-and-trough features just offshore from a mudboil-covered till plain. These features are common in the more southerly tundra areas and occur exclusively on near-shore lake bottoms composed of till or other types of stoney mud, usually in less than 2 m of water (Shilts and Dean, 1975). These particular rib and trough structures seem to break up into individual, isolated, irregularly shaped masses offshore. For further explanation, see extended caption for image 0120.