What was the most devastating eruption in new zealand?

Answer 1

The Oaranui eruption of the Taupo Volcanic Zone, about 26 500 years ago, was the largest recent volcanic event in the world. This probably erupted about 1200 cubic kilometres of material. This reached VEI-8 on the Volcanic Explosivity Index, the highest rating available.

A more recent event directly from Taupo itself was in 181CE, and is known from red sky reports from both Chinese and Roman sources. This erupted about 120 cubic kilometres of material. This emptied the lake, and ejected about 30 cubic kilometres of material in a few minutes. There are still steaming cliffs towards the south of the lake.

In the last 27 000 years, it has erupted 28 times, and this leads some to consider an eruption likely or overdue, but volcanoes are not regular clocks.