While on descent of Murchison falls with a friend, we observed a significant ice collapse from the upper climbers left hand ice pillars. We were in the cave at the third rappel station when the release occurred. The collapse sent significant amounts of debris down the entire width of the climb. We observed ice chunks as far as 100m below the gear up spot. We very lucky to have been in the cave and on that side of the climb. Had we been anywhere else we would have struck by debris.
Once low enough we were able to see that a major portion of the upper left hand pillars had collapsed.
The collapse occurred at approximately 13:45. Temps at the base in the morning were around -15. Aside from normal daytime warming we did not see any major spikes in temperature throughout the day.

A very sobering experience!