What is the smallest volcano in new zealand?

Who knows? There is a tiny one called Haughton Hill in the Maniototo, whos hummock barely makes it above the surface of the plain. And on the nearby Rock and Pillar Range, there is an explosion crater that has no significant eruptive material. And no doubt many more such round the country. OOPS! got the name wrong there. It is Haughton Hill in the Maiototo.