Glacial landforms with dimensions smaller than the imaging capability of the first-generation multibeam sonars will become a more frequent topic as high-resolution seafloor mapping technology advances. In Pine Island Bay (PIB) glacial trough, West Antarctica, small regular ridges of only a few metres from trough to crest were mapped in water depths of about 700 m. The small size of these ridges is at the limit of what modern deep-water multibeam sonars are capable of mapping. The ridges are interpreted to have been formed at the trailing edge of mega-icebergs moving up and down in response to tides while ploughing the seafloor (Jakobsson et al. 2011). The mega-icebergs in PIB were produced by ice shelf break-up and associated grounding-zone retreat.