On the back of the photo, it says, "The Rock (Maungarahoe), near Dargaville." Maungaraho Rock today.
These two may be of the same event. Both were taken by "J. Batchelor, Film Specialist, Whangarei". If that's John Batchelor, then the Auckland City Library photographers database lists him as operating around the years 1925-1932. Which would fit, because the speaker (detail below) sure looks like Gordon Coates.
What was happening, I don't know.