Over the last 30 years the Erebus Glacier Tongue has been the subject of numerious theoretical and experimental investigations which have assumed that the observed alternating strains are standing waves. Since November 1984 we have monitored the strain of the Erebus Glacier Tongue with two strain meters placed on either side of the Tongue and more recently with strain meters along the Tongue. Our data imply that flexural-gravity waves are travelling from the snout with a phase speed of and a wavelength of . We suggest these waves are generated by surface gravity waves or seiches which, when resolved along the Tongue, produce waves travelling near the minimum phase speed for flexural-gravity waves. Our observations do not support standing wave theories for the calving of glacier tongues but suggest that the calving of the Erebus Glacier Tongue on 1 March 1990 occurred when sea waves produced a large lateral force on the Tongue while it was exposed to open water.