Trendall was the geologist on the 1951-52 and 1953-54 South Georgia Survey expeditions led by Duncan Carse. Trendall Crag, 1,005 m, overlooking the north side of Drygalski Fjord at the southeast end of South Georgia, was named to commemorate Alec Trendall's contribution. In 2011 he published a full account of the survey expeditions, entitled Putting South Georgia on the Map.